Method for removing iodine in macroalgae and application

Abstract

The invention belongs to a biological deiodination technology, and provides a method for removing iodine in macroalgae and application. The chlamydomonas reinhardtii has an adsorption effect on iodine-containing substances and can be used for biological deiodination of macroalgae. Specifically, the invention provides a biological adsorption deiodination technology for removing iodine contained in edible macroalgae such as sargassum fusiforme, kelp, undaria pinnatifida and porphyra haitanensis through incubation treatment by using chlamydomonas reinhardtii in water, and a specific incubation treatment process is optimized, so that a relatively high deiodination effect is achieved.

Description

Technical Field

[0001] This invention relates to the field of biological deiodination technology, specifically to a method and application for removing iodine from large seaweeds. More specifically, it relates to a deiodination technology using *Chlamydomonas reinhardtii* to remove iodine from edible large seaweeds such as Sargassum fusiforme, kelp, wakame, and nori, and the application of this technology in the processing of low-iodine seaweed foods. Background Technology

[0002] Iodine is an essential nutrient for the human body and can usually be obtained through a balanced diet. Long-term iodine deficiency can lead to goiter and its complications, such as hypothyroidism and intellectual disability. However, excessive iodine intake over a long period can also harm the body, causing diseases such as hyperthyroidism and iodine-induced goiter.

[0003] Sargassum fusiforme, kelp, wakame, and nori are all edible large seaweeds rich in iodine, making them excellent sources of iodine. They are also rich in amino acids, vitamins, minerals, dietary fiber, unsaturated fatty acids, fucoidan, and other nutrients and functional components, making them extremely nutritious dietary materials. Currently, with the continuous improvement of people's living standards and health levels, the social demand for low-iodine seaweed nutritional foods such as iodine-free Sargassum fusiforme and its processed products is also constantly increasing.

[0004] Chinese invention patent CN106998776A discloses a method for manufacturing brown algae with reduced iodine content. Specifically, untreated brown algae raw materials are chopped, then heated in hot water at 90-100℃ for 90-300 seconds, followed by extraction with an ethanol-containing solution. This method can reduce the iodine content to an ingestible level while preserving the pigment components of the brown algae, making it suitable for long-term consumption. However, while achieving iodine removal from the algae, this method inevitably causes the destruction or loss of some nutritional components. For example, some heat-sensitive nutritional components are destroyed by heat, while some alcohol-soluble nutritional components are lost due to extraction with the ethanol-containing solution.

[0005] Existing techniques (Approaches for reducing the iodine content of the brownseaweed Saccharina latissima—effects on sensory properties, Journal of Applied Phycology [J], Krook JL et al. (2024) 36:783-796.) have investigated the effects of steam or warm water treatment on the iodine content, nutrient composition, and sensory properties of the brown seaweed Saccharina latissima. The results showed that warm water treatment reduced the dry weight iodine content by 73% and 59%, respectively. However, during the warm water treatment process, freshwater treatment resulted in greater loss of soluble nutrients (mainly carbohydrates and minerals), while seawater treatment retained more nutrients, although the proportion of minerals changed.

[0006] Chlamydomonas reinhardtii ( Chlamydomonas reinhardi Dang.) belongs to the genus Chlamydomonadaceae. Chlamydomonas Chlamydomonas reinhardtii is a single-celled eukaryotic freshwater green alga. Its growth is affected by light, temperature, nutrients, and water quality. It can grow photosynthetically autotrophically, heterotrophically, or a mixture of photosynthetically autotrophic and heterotrophic growth. Chlamydomonas reinhardtii is relatively easy to cultivate and reproduce, and grows rapidly under suitable conditions, achieving a high biomass in a short period of time. The existing technology (Research progress on the molecular defense mechanism of Chlamydomonas reinhardtii in response to heavy metal stress, Biotechnology Bulletin [J], 2025, 41(8): 53-64.) introduces the key components and regulatory mechanisms of Chlamydomonas reinhardtii in response to heavy metal stress, and combines modern molecular biology technology to study the modification of Chlamydomonas reinhardtii's heavy metal bioremediation capacity. Current research on the use of Chlamydomonas reinhardtii for wastewater treatment shows that the removal rates of heavy metals Fe(II), Cu(II), Zn(II), and Mn(II) in wastewater by Chlamydomonas reinhardtii are 87%, 68%, 60%, and 100%, respectively.

[0007] Chlamydomonas reinhardtii exhibits unique capabilities in the biotransformation and bioadsorption of metals, and has been applied in many scientific studies as an important model organism and a classic model for basic biological research. However, no research has been reported to date on the use of Chlamydomonas reinhardtii for iodine removal from edible macroalgae such as Sargassum fusiforme. Summary of the Invention

[0008] To address the problems existing in current technologies, this invention provides a method and application for removing iodine from large seaweeds. This invention discovers that *Chlamydomonas reinhardtii* can accumulate iodine on its surface through bioadsorption of iodine-containing substances, thereby achieving iodine removal from large seaweeds such as *Sargassum fusiforme*. Based on this, a bioadsorption iodine removal technology for *Chlamydomonas reinhardtii* was established. The cell walls of *Chlamydomonas reinhardtii* contain biomolecules such as polysaccharides and proteins, and their surfaces bear functional groups such as hydroxyl, carboxyl, and amino groups. Therefore, *Chlamydomonas reinhardtii* may be able to bind iodine or iodine-containing substances through electrostatic attraction, coordination, and other mechanisms, undergoing complexation and ion exchange reactions to fix iodine, iodized salts, or organic iodine molecules on the cell surface, thus achieving bioadsorption iodine removal. This method has the potential to be used for iodine removal from various edible large seaweeds such as *Sargassum fusiforme*, kelp, wakame, and *Porphyra yezoensis*.

[0009] Terminology Explanation: Unless otherwise defined, all technical terms in this document have the same meanings as commonly understood by one of ordinary skill in the art to which the subject matter of the claims pertains. Unless otherwise stated, all patents, patent inventions, and publications cited in this document are incorporated herein by reference in their entirety. If multiple definitions exist for terms in this document, the definitions in this chapter shall prevail.

[0010] It should be understood that the above brief description and the following detailed description are exemplary and for illustrative purposes only, and do not limit the subject matter of the invention in any way. In this invention, the singular is used in conjunction with the plural unless otherwise specifically stated. It should also be noted that, unless otherwise stated, the use of “or” or “or” means “and / or”. Furthermore, the use of the term “comprising” and other forms such as “including,” “containing,” and “contains” are not limiting.

[0011] The definitions of standard chemical terms can be found in the reference "Chemical Industry Dictionary, 2nd Edition. Edited by Wang Zhen. Beijing: Chemical Industry Press, April 1985."

[0012] Unless otherwise stated, conventional methods within the scope of the art shall be used.

[0013] Unless specifically defined herein, the use of all commercially available products herein employs standard techniques. For example, it may be carried out using the manufacturer's instructions for use with the kit, or in accordance with methods known in the art or the description of this invention. The techniques and methods described herein can generally be implemented according to conventional methods well known in the art, based on the descriptions in the various summary and more specific documents cited and discussed in this specification.

[0014] The terms “optional / arbitrary” or “optionally / arbitrarily” mean that the event or situation described below may or may not occur, including both the occurrence and non-occurrence of the event or situation.

[0015] The term "Chlamydomonas reinhardtii concentration % or % (w / v)" used in this article refers to the concentration of Chlamydomonas reinhardtii in a suspension of water (tap water or purified water), which is equivalent to g / 100mL.

[0016] The term "solid-liquid ratio" as used in this article refers to the mass-to-volume ratio of the raw seaweed and Chlamydomonas reinhardtii suspension in water (tap water or purified water), expressed in g / mL.

[0017] The technical solution of the present invention is as follows: In a first aspect, the present invention provides the application of Chlamydomonas reinhardtii in the deiodination of seaweed.

[0018] In some specific embodiments of the present invention, the seaweed includes one or more of Sargassum fusiforme, kelp, wakame seaweed, and Porphyra yezoensis.

[0019] The research results of this invention show that incubating seaweed with Chlamydomonas reinhardtii can effectively reduce the iodine content in edible large seaweeds. Chlamydomonas reinhardtii is a recognized safe food ingredient. Therefore, the Chlamydomonas reinhardtii bio-adsorption deiodination technology of this invention can be used in the food industry, specifically for processing and producing low-iodine seaweed ingredients such as deiodized Sargassum fusiforme, kelp, wakame seaweed, and Porphyra yezoensis.

[0020] Secondly, the present invention also provides a method for removing iodine from seaweed, the method comprising: taking Chlamydomonas reinhardtii and adding it to a medium of water to obtain a Chlamydomonas reinhardtii suspension; adding seaweed to the Chlamydomonas reinhardtii suspension at a certain solid-liquid ratio for incubation treatment to complete the deiodination of seaweed.

[0021] In this invention, the medium water is not specifically limited and can be tap water or purified water, etc. Different forms of water will not affect the deiodination effect of Chlamydomonas reinhardtii.

[0022] In some preferred embodiments of the present invention, the concentration of Chlamydomonas reinhardtii in the suspension is 0.1-20% (w / v), and the incubation time is 10-200 min; In some preferred embodiments of the present invention, the concentration of Chlamydomonas reinhardtii in the suspension is 0.1-5% (w / v), and the incubation time is 20-180 min.

[0023] In some specific embodiments of the present invention, the seaweed is Sargassum fusiforme, the concentration of Chlamydomonas reinhardtii in the suspension is 0.1-10% (w / v), and the incubation time is 30-180 min; Preferably, the concentration of *Chlamydomonas reinhardtii* in the suspension is 0.5-10% (w / v), and the incubation time is 60-120 min; or the concentration of *Chlamydomonas reinhardtii* in the suspension is 2% (w / v), and the incubation time is 60 min; or the concentration of *Chlamydomonas reinhardtii* in the suspension is 5-10% (w / v), and the incubation time is 30 min.

[0024] In some other specific embodiments of the present invention, the seaweed is kelp, the concentration of Chlamydomonas reinhardtii in the Chlamydomonas reinhardtii suspension is 0.1-2% (w / v), and the incubation time is 60-180 min; Preferably, the concentration of *Chlamydomonas reinhardtii* in the suspension is 0.1-0.5% (w / v), and the incubation time is 60-120 min; or the concentration of *Chlamydomonas reinhardtii* in the suspension is 1-2% (w / v), and the incubation time is 60 min.

[0025] In some other specific embodiments of the present invention, the seaweed is wakame, the concentration of Chlamydomonas reinhardtii in the suspension is 0.1-5% (w / v), and the incubation time is 60-180 min; Preferably, the concentration of Chlamydomonas reinhardtii in the suspension is 0.5-2% (w / v), and the incubation time is 120-180 min. More preferably, the concentration of Chlamydomonas reinhardtii in the suspension is 1-2% (w / v), and the incubation time is 120-180 min; More preferably, the concentration of Chlamydomonas reinhardtii in the suspension is 2% (w / v), and the incubation time is 120 min.

[0026] In some other specific embodiments of the present invention, the seaweed is Porphyra yezoensis, the concentration of Chlamydomonas reinhardtii in the suspension is 0.1-2% (w / v), and the shaking incubation time is 60-180 min; Preferably, the concentration of *Chlamydomonas reinhardtii* in the suspension is 0.1-0.5% (w / v), and the shaking incubation time is 120-180 min; more preferably, the concentration of *Chlamydomonas reinhardtii* in the suspension is 0.1-0.5% (w / v), and the shaking incubation time is 180 min; Preferably, the concentration of *Chlamydomonas reinhardtii* in the suspension is 1-2% (w / v), and the shaking incubation time is 60-180 min; more preferably, the concentration of *Chlamydomonas reinhardtii* in the suspension is 1-2% (w / v), and the shaking incubation time is 120-180 min; even more preferably, the concentration of *Chlamydomonas reinhardtii* in the suspension is 1-2% (w / v), and the shaking incubation time is 180 min.

[0027] In some preferred embodiments of the present invention, the concentration of Chlamydomonas reinhardtii in the suspension is 0.1-20% (w / v), the solid-liquid ratio is 1:2.5-1:100, and the mass ratio of seaweed to Chlamydomonas reinhardtii is 1:0.05-1:1; Preferably, the concentration of *Chlamydomonas reinhardtii* in the suspension is 0.5-10% (w / v), the solid-liquid ratio is 1:2.5-1:50, and the mass ratio of seaweed to *Chlamydomonas reinhardtii* is 1:0.1-1:0.5. Preferably, the concentration of Chlamydomonas reinhardtii in the suspension is 10-20% (w / v), the solid-liquid ratio is 1:2.5-1:5, and the mass ratio of seaweed to Chlamydomonas reinhardtii is 1:0.2-1:0.5.

[0028] In some preferred embodiments of the present invention, the incubation treatment is an oscillation incubation treatment or a stirring incubation treatment; the incubation temperature is 15-30°C, preferably 20-25°C, more preferably 25°C; and / or the oscillation frequency of the oscillation incubation treatment and / or the stirring speed of the stirring incubation treatment is 100-200 rpm; preferably 150-200 rpm; more preferably 200 rpm.

[0029] It should be noted that, in terms of processing methods, this invention provides various stirring modes such as oscillating stirring under room temperature or temperature-controlled conditions, continuous rotary stirring, or manual intermittent stirring. Existing technologies capable of achieving mixing effects comparable to stirring speeds of 100-200 rpm are all within the scope of protection of this invention. Those skilled in the art can choose any one or more combinations of incubation methods according to their own conditions and needs. Therefore, the embodiments of this invention are flexible and diverse, highly practical, and suitable not only for large enterprises for automated large-scale production but also for micro-enterprises for manual or semi-automated small-scale production.

[0030] In some specific embodiments of the present invention, the large seaweed to be treated needs to be pretreated before incubating Chlamydomonas reinhardtii. For example, before incubation, the large seaweed is stored at 0-8°C, and before adding Chlamydomonas reinhardtii suspension, the impurities attached to the surface of the seaweed are washed with tap water, and then the surface moisture is wiped off with absorbent paper for later use.

[0031] Compared with the prior art, the present invention has the following beneficial effects: This invention discovers that *Chlamydomonas reinhardtii*, when suspended in water, can adsorb and concentrate iodine on itself through biosorption of iodine-containing substances, thereby removing iodine from the treated seaweed and reducing the iodine content in large edible seaweeds such as Sargassum fusiforme, kelp, wakame, and nori. This has broad application prospects in the preparation of low-iodine food ingredients.

[0032] Furthermore, this invention has conducted in-depth research on the iodine removal process of Chlamydomonas reinhardtii. By further optimizing the incubation temperature, time, incubation method, Chlamydomonas reinhardtii concentration, and the solid-liquid ratio of raw materials to Chlamydomonas reinhardtii suspension, not only has a better iodine removal effect been achieved, but the iodine removal efficiency has also been greatly improved. For example, for large seaweeds such as Sargassum fusiforme and Porphyra yezoensis, which have no iodine removal effect when incubated with water as a solvent, the iodine removal effect can be significantly improved by adding Chlamydomonas reinhardtii incubation treatment. For large seaweeds such as kelp and wakame, which have a certain iodine removal effect when incubated with water as a solvent, the iodine removal rate can be further improved by adding Chlamydomonas reinhardtii incubation treatment. It also has many advantages such as shortened incubation time, reduced solvent volume, and improved iodine removal efficiency.

[0033] In addition, the bio-adsorption deiodination technology of the present invention only requires incubation in water at room temperature for several tens of minutes when deiodizing seaweed. The solvent does not contain ethanol, no heating is required, the water consumption is small, and the incubation time is short. It overcomes the shortcomings of the prior art in that heat-sensitive nutritional components are destroyed by heat and that alcohol-soluble nutritional components are lost due to extraction with ethanol-containing solvents.

[0034] In summary, the biological deiodination process of Chlamydomonas reinhardtii based on this invention does not cause any loss or damage to the nutritional components of seaweed, thus ensuring that the basic nutritional value of the food is not affected. Detailed Implementation

[0035] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products. All reagents used are analytical grade reagents.

[0036] In the following embodiments, the Chlamydomonas reinhardtii used was commercially available Chlamydomonas reinhardtii powder, which was live algae powder. It was purchased from Xi'an Tianguangyuan Biotechnology Co., Ltd. on September 19, 2025 (batch number TGY20250809-1, date 2025.08.09, shelf life 24 months, specification 99%). The algae powder was stored in a room temperature warehouse for experimental research of the present invention.

[0037] In the following embodiments, the edible large seaweed raw material referred to as Sargassum fusiforme was fresh Sargassum fusiforme with intact thallus, which was provided by Zhejiang Jinhaiyun Biotechnology Co., Ltd. on August 1, 2025. Part of the raw material was stored in a 4°C refrigerator for experimental research use in this invention, while the remaining part was frozen in a -20°C refrigerator for thawing when the raw material in the 4°C refrigerator was exhausted. The edible large seaweed raw materials referred to as kelp, wakame, and nori were all commercially available food raw materials purchased on September 21, 2025. Kelp and wakame were fresh, and nori was dried nori produced in Cangnan. The fresh kelp and wakame were stored in a 4°C refrigerator, while the dried nori was stored in a room temperature warehouse for experimental research use in this invention.

[0038] In the following examples, the iodine content in edible macroalgae samples and Chlamydomonas reinhardtii samples was determined using the "second method of redox titration" in the national standard "GB 5009.267-2020 National Food Safety Standard - Determination of Iodine in Food".

[0039] Example 1: Investigation of the effects of purified water and tap water on the deiodination of Chlamydomonas reinhardtii This embodiment uses Sargassum fusiforme as the research subject and water (purified water and tap water) as the medium. Sargassum fusiforme was incubated with Chlamydomonas reinhardtii in purified water and tap water, respectively. The changes in iodine content in Sargassum fusiforme before and after incubation were analyzed, as well as the iodine removal rate and Chlamydomonas reinhardtii iodine removal rate of each treatment group. This demonstrates the iodine removal effect of Chlamydomonas reinhardtii on the iodine content in Sargassum fusiforme. Simultaneously, the effects of two different water qualities on the iodine removal effect of Chlamydomonas reinhardtii were compared.

[0040] (1) Treatment of Sargassum fusiforme with Chlamydomonas reinhardtii in purified water and tap water 1.1 Incubation Treatment Experiment in Purified Water: Nine 500 mL Erlenmeyer flasks were divided into three groups: a solvent control group (purified water), a 0.1% Chlamydomonas reinhardtii purified water group, and a 1% Chlamydomonas reinhardtii purified water group, with three flasks in each group. In the solvent control group, 500 mL of purified water was added to each of the three Erlenmeyer flasks. In the 0.1% Chlamydomonas reinhardtii purified water group, 0.5 g of Chlamydomonas reinhardtii (weighed to an accuracy of 0.001 g) was added to each of the three Erlenmeyer flasks, followed by 500 mL of purified water. The mixture was then shaken well to prepare a 0.1% Chlamydomonas reinhardtii purified water suspension. In the 1% Chlamydomonas reinhardtii purified water group, 5.0 g of Chlamydomonas reinhardtii (weighed to an accuracy of 0.001 g) was added to each of the three Erlenmeyer flasks, followed by 500 mL of purified water. The mixture was then shaken well to prepare a 1% Chlamydomonas reinhardtii purified water suspension. Take an appropriate amount of Sargassum fusiforme from a 4℃ refrigerator, wash off any impurities on the surface of the algae with tap water, and then wipe off the surface moisture with absorbent paper. Weigh out 9 test samples, each approximately 10 g, and add them to the 9 Erlenmeyer flasks. Then, load all 9 Erlenmeyer flasks onto a shaker fixture and incubate at 25℃ and 200 rpm. Samples are taken at 60 min, 120 min, and 180 min of incubation to determine the iodine content (sampling and subsequent processing are as follows: at each time point, remove one Erlenmeyer flask from each group, including one for the solvent control purified water group, one for the 0.1% Chlamydomonas reinhardtii purified water group, and one for the 1% Chlamydomonas reinhardtii purified water group; immediately after sampling, proceed with subsequent processing: for the solvent control purified water group, after removing the Sargassum fusiforme from the Erlenmeyer flask, wipe off the surface moisture with absorbent paper, weigh approximately 10 g (accurate to 0.001 g) of sample, and place it in a 50℃ container). For the 0.1% *Chlamydomonas reinhardtii* purified water group and the 1% *Chlamydomonas reinhardtii* purified water group, after removing the *Sargassum fusiforme* from the *Chlamydomonas reinhardtii* water, the surface of the *Sargassum fusiforme* was first quickly washed with purified water to remove any adhering *Chlamydomonas reinhardtii*, and then the surface moisture was wiped off with absorbent paper. Approximately 10 g (accurate to 0.001 g) of the sample was then weighed and placed in a 50 mL crucible for later use. All samples will be used together for the following experiments to determine the iodine content.

[0041] 1.2 Incubation Treatment Experiment in Tap Water: This experiment was conducted simultaneously with the incubation treatment experiment in purified water described above. Except for using tap water instead of purified water, the experimental methods were identical to those in the purified water incubation treatment experiment. Thus, the following samples were obtained: a solvent control group (tap water group), a 0.1% Chlamydomonas reinhardtii tap water group, and a 1% Chlamydomonas reinhardtii tap water group. These samples underwent the same shaking incubation treatment at 25℃ and 200 rpm for 60 min, 120 min, and 180 min, respectively. Three samples of Sargassum fusiforme treated in tap water and six samples of Sargassum fusiforme incubated in tap water with Chlamydomonas reinhardtii were also obtained. Approximately 10 g (accurate to 0.001 g) of each sample was weighed and placed in a 50 mL crucible for iodine content determination.

[0042] 1.3 The iodine removal rate in each group of Sargassum fusiforme was calculated based on the iodine content of untreated Sargassum fusiforme (100%). Therefore, in the iodine content determination experiment, a special untreated group was set up. Three samples of different masses were weighed and measured, and the average value was taken as the iodine content in the untreated group of Sargassum fusiforme, which was used to calculate the iodine removal rate. The untreated Sargassum fusiforme samples were Sargassum fusiforme stored in a 4℃ refrigerator without incubation treatment. After being taken out of the refrigerator, the surface moisture was wiped off with absorbent paper, and three samples of approximately 10, 20, and 30 g (accurate to 0.001 g) were weighed and placed in 50 mL crucibles for use in the following iodine content determination experiments.

[0043] (2) Determination of iodine content in Sargassum fusiforme samples The iodine content in Sargassum fusiforme samples was determined using the "second method, redox titration method" from the national standard "GB 5009.267-2020 National Food Safety Standard - Determination of Iodine in Food".

[0044] 2.1 Principle of Iodine Content Determination After carbonization and ashing, the sample was subjected to oxidative oxidation of iodide ions to iodate ions (I) using liquid bromine in an acidic medium. - + 3Br2 + 3H2O → IO3 - + 6H + + 6Br - Iodate ions oxidize potassium iodide in acidic solutions to precipitate iodine molecules I2 (IO3). - + 5I - + 6H + → 3I₂ + 3H₂O). Starch is particularly sensitive to I₂, and can complex and adsorb trace amounts of I₂, turning blue, but it does not react with iodide ions (I₂). - However, it does not exhibit any color. Therefore, using starch as an indicator, starch solution is added to turn the sample solution blue, and titration is performed with sodium thiosulfate standard solution until the blue color just disappears. At this point, all iodine molecules (I₂) in the solution have been completely reduced to iodide ions (I₂O₃) by sodium thiosulfate. - (I2+ 2S2O3 2- → 2I - + S4O6 2- After titration, record the volume of sodium thiosulfate standard solution consumed and calculate the iodine content in the sample.

[0045] 2.2 Method for determining iodine content Preparation of reagent and standard solutions: All reagent and standard solutions used below were prepared in strict accordance with the methods and requirements of the "Second Method: Oxidation-Reduction Titration" in the national standard "GB 5009.267-2020 National Food Safety Standard: Determination of Iodine in Food". Potassium iodide solution and starch solution were prepared fresh for each use, and the 0.010 mol / L sodium thiosulfate standard solution for titration was prepared by diluting 0.100 mol / L sodium thiosulfate standard stock solution 10 times before use.

[0046] Arcineration and ashing of Sargassum fusiforme samples and preparation of sample solution: The crucible containing the Sargassum fusiforme sample was placed in a muffle furnace and arcinated at 550°C for 40 min. After the furnace temperature cooled to room temperature, the crucible was removed. The arcinated residue of Sargassum fusiforme in the crucible was pure white, grayish-white, or gray, i.e., pure white residue, grayish-white residue, and gray residue were mixed together. A small amount of purified water was added to the crucible for grinding. After grinding, all the aqueous solution and residue in the crucible were transferred to a 250 mL beaker. The crucible was then rinsed several times with small amounts of purified water. All the rinsing liquid was combined into the beaker, and the total volume of the solution in the beaker was about 100 mL. After boiling for 5 min, the solution was filtered through filter paper while hot into a 250 mL iodine flask. The solution was slightly yellow. After cooling to room temperature, it was used as the Sargassum fusiforme sample solution. The iodine flask was then used directly for the following titration experiments.

[0047] Take another 250 mL iodine flask, add 100 mL of purified water, and use it as a blank solution for blank tests in the following redox titration experiments.

[0048] Redox titration experiment: Take the iodine flasks containing the Sargassum fusiforme sample solution and blank solution, and add 3 drops of 1 g / L methyl orange aqueous solution to each. Shake well; the solution is pale yellow. Adjust the color to pink using 1 mol / L sulfuric acid solution. In practice, the color is adjusted by adding 1 mol / L sulfuric acid solution dropwise while shaking and observing until the solution color changes from pale yellow to pink. Then add 5 mL of saturated bromine water, shake well, and the solution changes from pink to orange-yellow. Heat to boiling until the yellow color disappears. At this point, iodide ions in the sample solution are oxidized to iodate ions (I₂O₃). - + 3Br2 + 3H2O → IO3 - + 6H + + 6Br -After slightly cooling, add 5 mL of a 200 g / L sodium formate aqueous solution, heat to boiling for 2 min, cool in a water bath to below 30°C, then add 5 mL of a 3 mol / L sulfuric acid solution and 5 mL of a 150 g / L potassium iodide aqueous solution. Cover the bottle and let it stand in the dark for 10 min. During this process, iodate ions in the sample solution oxidize potassium iodide under acidic conditions to produce free iodine molecules I₂ (IO₃). - + 5I - + 6H + → 3I₂ + 3H₂O). The different sample solutions exhibit varying shades of brownish-yellow due to differences in I₂ content → a certain color within the yellow spectrum. Generally, the sample solutions, due to their high I₂ content, are a deeper yellow. Therefore, it is advisable to initially titrate directly using the color change of the solution as an indicator until the color lightens, without adding starch indicator. Thus, the sample solution is first titrated with a 0.010 mol / L sodium thiosulfate standard solution until the solution turns light yellow. Then, 1 mL of a 5 g / L starch aqueous solution is added to both the sample solution and the blank solution. At this point, the sample solution turns a deep blue-blue-purple color due to the blue color of starch and the high I₂ content, while the blank solution is colorless or only slightly colored. Subsequently, titration with a 0.010 mol / L sodium thiosulfate standard solution continues until the blue color just disappears. At this point, the I₂ in the solution is just completely reduced to iodide ions by the added sodium thiosulfate. - Since no I2 has formed a complex with starch to produce color, the blue color of the solution has faded. After titration, record the total volume of sodium thiosulfate standard solution consumed before and after the addition of starch solution.

[0049] 2.3 Calculation of Iodine Content Iodine content is calculated using the following formula: X = [ ( V - V 0) × c × 21.15× f ] / m × 1000.

[0050] In the formula, X―― The content of iodine in the sample is expressed in milligrams per kilogram (mg / kg). V―― The volume of sodium thiosulfate standard solution consumed to titrate the sample solution, expressed in milliliters (mL); V 0 ―― The volume of sodium thiosulfate standard solution consumed to titrate the blank solution, expressed in milliliters (mL); c――The concentration of the sodium thiosulfate standard solution is expressed in moles per liter (mol / L). 21.15 ―― To titrate with 1.00 mL sodium thiosulfate standard solution [ c [(Na2S2O3) = 0.100 mol / L] is the equivalent mass of iodine, expressed in grams per mole (g / mol). f ―― This refers to the dilution factor of the sample. m ―― The mass of the sample is expressed in grams (g). 1000 ―― Unit conversion factor.

[0051] In this embodiment c It is 0.01. f It is 10.

[0052] 2.4 Calculation of Iodine Removal Rate The iodine removal rate (%) of each treatment group was calculated using the iodine content of the untreated group as a baseline (100%), according to the following formula: Iodine removal rate (%) = (Iodine content) 未孵育处理组 - Iodine content 处理组 ) / Iodine content 未孵育处理组 ×100%.

[0053] Among them, the treatment group refers to the solvent control group (solvent control purified water group or solvent control tap water group) or the Chlamydomonas reinhardtii group (Chlamydomonas reinhardtii purified water group or Chlamydomonas reinhardtii tap water group with different concentrations), the same below.

[0054] 2.5 Calculation of Iodine Removal Rate from Chlamydomonas reinhardtii The iodine removal rate of *Chlamydomonas reinhardtii* refers to the iodine removal rate that retains only the iodine removal contribution from adsorption by *Chlamydomonas reinhardtii* after deducting the contribution of solvent iodine removal under the same conditions. Therefore, it can be calculated using the following formula: Iodine removal rate of Chlamydomonas reinhardtii (%) = Iodine removal rate 莱茵衣藻组 - Iodine removal rate 溶媒对照组 .

[0055] The iodine removal rate of *Chlamydomonas reinhardtii* can also be understood as the percentage of iodine content in a sample that is further removed by *Chlamydomonas reinhardtii* after solvent immersion, relative to the iodine content of the untreated sample before deiodization treatment. Therefore, it can also be calculated using the following formula: *Chlamydomonas reinhardtii* iodine removal rate (%) = (iodine content) 溶媒对照组 - Iodine content 莱茵衣藻组 ) / Iodine content 未孵育处理组 ×100%.

[0056] (3) Experimental results The iodine content in the untreated group of Sargassum fusiforme, as well as the iodine content, deiodination rate, and iodine removal rate of each incubation group obtained by incubation in purified water or tap water with different concentrations of Chlamydomonas reinhardtii for different times, as measured by the above experiments, are shown in Table 1.

[0057] Table 1. Iodine content, iodine removal rate, and iodine removal rate of Chlamydomonas reinhardtii in each group of Sargassum fusiforme.

[0058] Table 1 shows that: 1) Compared with the untreated group, the iodine content in both the solvent control purified water group and the solvent control tap water group was not significantly reduced, and the iodine removal rate was less than 5%, indicating that the shaking treatment had no significant iodine removal effect in either the solvent control purified water group or the solvent control tap water group; 2) Compared with the untreated group, the iodine content in both the 0.1% and 1% Chlamydomonas reinhardtii incubation groups was significantly reduced, regardless of whether it was purified water or tap water. The iodine removal rate of the 0.1% Chlamydomonas reinhardtii group was in the range of 16%-30%, and that of the 1% Chlamydomonas reinhardtii group was in the range of 40%-60%. Whether in purified water or tap water, the iodine removal rate of the 1% Chlamydomonas reinhardtii group was more than twice that of the 0.1% Chlamydomonas reinhardtii group, indicating that the adsorption and iodine removal effect of 1% Chlamydomonas reinhardtii was more than twice that of 0.1% Chlamydomonas reinhardtii; 3) Comparing the Chlamydomonas reinhardtii group with the same concentration and incubation time between the purified water and tap water groups, the iodine removal rate and the iodine removal rate of Chlamydomonas reinhardtii were similar and had no significant difference, indicating that the two water qualities had almost no effect on the iodine removal effect of Chlamydomonas reinhardtii; 4) The iodine removal rate of Chlamydomonas reinhardtii was still low at 60 min in both purified water and tap water, reached a peak at 120 min, and declined at 180 min, indicating that 120 min is the optimal incubation time for iodine removal.

[0059] The above experimental results show that iodine in Sargassum fusiforme can be adsorbed and removed by incubating with Chlamydomonas reinhardtii in water. Both purified water and tap water can be used for incubation, with comparable iodine removal efficiency. The two water qualities have no effect on the iodine removal effect of Chlamydomonas reinhardtii. Therefore, Chlamydomonas reinhardtii can be used to remove iodine from Sargassum fusiforme, and for large-scale industrial production, incubation with tap water is recommended.

[0060] Example 2: Investigation of the effect of Chlamydomonas reinhardtii concentration on the iodine removal effect of macroalgae in tap water This embodiment uses Sargassum fusiforme as the subject. Sargassum fusiforme was incubated in tap water with different concentrations of Chlamydomonas reinhardtii, and the iodine content in Sargassum fusiforme was measured to examine the effect of Chlamydomonas reinhardtii concentration on the deiodination effect of Chlamydomonas reinhardtii.

[0061] (1) Treatment of Sargassum fusiforme with different concentrations of Chlamydomonas reinhardtii in tap water Take 15 500 mL Erlenmeyer flasks and divide them into 5 groups of 3. In one group, add 500 mL of tap water to each of the 3 Erlenmeyer flasks to serve as the solvent control (tap water group). In another group, add 0.5 g (weighed to 0.001 g) of *Chlamydomonas reinhardtii* to each of the 3 Erlenmeyer flasks, then add 500 mL of tap water to each, and shake well to prepare a 0.1% *Chlamydomonas reinhardtii* tap water suspension, designated as the 0.1% *Chlamydomonas reinhardtii* tap water group. In yet another group, add 2.5 g (weighed to 0.001 g) of *Chlamydomonas reinhardtii* to each of the 3 Erlenmeyer flasks, then add 500 mL of tap water to each, and shake well to prepare a 0.5% *Chlamydomonas reinhardtii* tap water suspension, designated as the 0.5% *Chlamydomonas reinhardtii* tap water group. In yet another group, add 5.0 g (weighed to 0.001 g) of *Chlamydomonas reinhardtii* to each of the 3 Erlenmeyer flasks, then add 500 mL of tap water to each... Mix 1 mL of water with tap water to prepare a 1% Chlamydomonas reinhardtii suspension, designated as the 1% Chlamydomonas reinhardtii tap water group. For the last group of three Erlenmeyer flasks, add 10.0 g of Chlamydomonas reinhardtii (weighed to an accuracy of 0.001 g) to each flask, then add 500 mL of tap water to each flask and mix well to prepare a 2% Chlamydomonas reinhardtii tap water suspension, designated as the 2% Chlamydomonas reinhardtii tap water group. Take an appropriate amount of fresh Sargassum fusiforme from a 4°C refrigerator, wash off any impurities adhering to the algal surface with tap water, and then wipe off the surface moisture with absorbent paper. Weigh out 15 samples of Sargassum fusiforme, approximately 10 g each, and add one sample to each of the 15 Erlenmeyer flasks. Then, load all 15 Erlenmeyer flasks onto a shaker fixture and incubate at 25°C and 200 rpm. Sampling and subsequent processing are the same as in Example 1.

[0062] (2) Determination of iodine content in Sargassum fusiforme samples The methods for determining iodine content and processing data are exactly the same as those in Example 1 above (except for the unincubated group, the determination of iodine content in the unincubated group is detailed in the notes in Table 2).

[0063] (3) Experimental results The iodine content in the untreated group of Sargassum fusiforme and the iodine content, deiodination rate and iodine removal rate of each group of Sargassum fusiforme treated with different concentrations of Chlamydomonas reinhardtii in tap water are shown in Table 2.

[0064] Table 2 Iodine content, iodine removal rate and Chlamydomonas reinhardtii iodine removal rate in each group of Sargassum fusiforme

[0065] Table 2 shows that: 1) Compared with the untreated group, the iodine content in the solvent control tap water group did not decrease significantly at any incubation time point, and the iodine removal rate was below 3.5%, indicating that the results are consistent with those in Example 1, and that shaking treatment in tap water has no significant iodine removal effect; 2) Compared with the solvent control tap water group, the iodine content in the Chlamydomonas reinhardtii incubation groups at different concentrations decreased significantly at each incubation time point, and the iodine removal rate of each concentration of Chlamydomonas reinhardtii group increased significantly with the increase of Chlamydomonas reinhardtii concentration; indicating that the adsorption and iodine removal effect of Chlamydomonas reinhardtii significantly increases with its concentration; 3) Among the tap water groups of each concentration of Chlamydomonas reinhardtii, the iodine removal rate of the 1% and below concentration groups reached its peak at 120 min of incubation, and then slightly decreased or remained at that level, while the iodine removal rate of the 2% concentration group reached 60% at 60 min of incubation, and then remained basically unchanged, suggesting that the adsorption of iodine by 2% Chlamydomonas reinhardtii may have reached saturation at 60 min of incubation. Therefore, at concentrations of 1% and below, *Chlamydomonas reinhardtii* requires an incubation period of 120 min to reach its peak for iodine adsorption and removal, but this incubation time is reduced to 60 min at a concentration of 2%. This suggests that at higher concentrations of 5% or above, the incubation time required to reach the peak for iodine removal may be shortened to 30 min or less.

[0066] Example 3: Investigation of the effect of solid-liquid ratio of Sargassum fusiforme and Chlamydomonas reinhardtii suspension in tap water on the iodine removal process of Chlamydomonas reinhardtii. This embodiment uses Sargassum fusiforme as the subject. A 1% Chlamydomonas reinhardtii tap water suspension and a 120-minute incubation time for which the deiodination effect reaches its peak were used. Equal amounts of fresh Sargassum fusiforme samples were placed in the 1% Chlamydomonas reinhardtii tap water suspension at different solid-liquid ratios and incubated at 25°C and 200 rpm for 120 minutes on a shaker. The iodine content, deiodination rate, and iodine removal rate of Sargassum fusiforme and Chlamydomonas reinhardtii were measured to investigate the effect of solid-liquid ratio on the deiodination effect of Chlamydomonas reinhardtii.

[0067] (1) Incubation treatment of Sargassum fusiforme and 1% Chlamydomonas reinhardtii tap water at different solid-liquid ratios Take eight 250 mL and two 500 mL Erlenmeyer flasks and divide them into two groups of five each, including four 250 mL flasks and one 500 mL flask. One group of five Erlenmeyer flasks was filled with 50, 100, 150, 200, and 500 mL of tap water, respectively, to serve as the tap water control group with solid-liquid ratios of 1:5, 1:10, 1:15, 1:20, and 1:50. Another group of five Erlenmeyer flasks was filled with 0.5, 1.0, 1.5, 2.0, and 5.0 g of *Chlamydomonas reinhardtii* (weighed to 0.001 g), respectively, followed by 50, 100, 150, 200, and 500 mL of tap water. The solutions were shaken well to prepare 1% *Chlamydomonas reinhardtii* tap water suspensions, which were then used as 1% *Chlamydomonas reinhardtii* incubation treatment groups with solid-liquid ratios of 1:5, 1:10, 1:15, 1:20, and 1:50. Take an appropriate amount of fresh Sargassum fusiforme from a 4°C refrigerator, wash off any impurities on the surface of the thallus with tap water, and then wipe off the surface moisture with absorbent paper. Weigh out 10 samples, each approximately 10 g, and add one sample to each of the 10 Erlenmeyer flasks. Then, place all 10 Erlenmeyer flasks on a shaker and incubate at 25°C and 200 rpm for 120 min. Stop shaking to terminate the incubation. The sampling and subsequent processing procedures after incubation are the same as in Example 1.

[0068] (2) Determination of iodine content in Sargassum fusiforme samples The methods for determining iodine content and processing data are exactly the same as those in Example 1 above.

[0069] (3) Experimental results The iodine content in the untreated group of Sargassum fusiforme, as well as the iodine content, deiodination rate, and iodine removal rate of each incubation group obtained by incubation in tap water and 1% Chlamydomonas reinhardtii tap water suspension for 120 min at different solid-liquid ratios, are shown in Table 3.

[0070] Table 3 Iodine content, iodine removal rate and Chlamydomonas linteus iodine removal rate in each group of Sargassum fusiforme samples

[0071] As shown in Table 3, 1) Compared with the untreated group, the iodine content in each solid-liquid ratio tap water group did not decrease significantly, and the iodine removal rate was below 4.5%, indicating that the results in Examples 1 and 2 were consistent, and the shaking treatment in tap water did not have a significant iodine removal effect on the iodine contained in Sargassum fusiforme; 2) Compared with the untreated group, the iodine content in each solid-liquid ratio tap water incubation group of Chlamydomonas reinhardtii was significantly reduced, and was significantly lower than that in the solvent control tap water group. However, the iodine removal rate in each solid-liquid ratio tap water group of Chlamydomonas reinhardtii was significantly higher than that in the solvent control tap water group, indicating that Chlamydomonas reinhardtii showed a significant adsorption and iodine removal effect in each solid-liquid ratio experiment; 3) From the changes in the data within each solid-liquid ratio tap water group of Chlamydomonas reinhardtii, the iodine content decreased with the increase of the solid-liquid ratio, while the iodine removal rate increased significantly with the increase of the solid-liquid ratio. However, in each solid-liquid ratio solvent control tap water group, the iodine content and iodine removal rate did not show this regular trend. In this experiment, the mass of *Sargassum fusiforme* in each group was the same, 10 g, and the concentration of *Chlamydomonas reinhardtii* in each group was also the same, 1%. However, the total amount of *Chlamydomonas reinhardtii* in the incubation solution varied depending on the volume of the *Chlamydomonas reinhardtii* suspension used. The total amount of *Chlamydomonas reinhardtii* in the groups with solid-liquid ratios of 1:5, 1:10, 1:15, 1:20, and 1:50 was 0.5, 1, 1.5, 2, and 5 g, respectively. The mass ratio of *Sargassum fusiforme* to *Chlamydomonas reinhardtii* in each group was 1:0.05, 1:0.1, 1:0.15, 1:0.2, and 1:0.5, respectively. Each group was treated with the same amount of *Sargassum fusiforme* incubated with different amounts of *Chlamydomonas reinhardtii*. The more *Chlamydomonas reinhardtii*, the stronger its adsorption and deiodination effect. This is consistent with the changes in the iodine removal rate of *Chlamydomonas reinhardtii* shown in Table 3.

[0072] The iodine removal rate of *Chlamydomonas reinhardtii* does not include the contribution of iodine removal through soaking in tap water, but only the contribution of adsorption iodine removal by *Chlamydomonas reinhardtii*. Therefore, it can be considered a direct indicator of the strength of the adsorption iodine removal effect of *Chlamydomonas reinhardtii*. As shown in Table 3, the iodine removal rate of *Chlamydomonas reinhardtii* increases significantly with increasing solid-liquid ratio, indicating that the adsorption iodine removal effect of *Chlamydomonas reinhardtii* in each group increases sequentially with increasing solid-liquid ratio, which is consistent with the sequential increase in the total amount of *Chlamydomonas reinhardtii* in each group. This also suggests that if the solid-liquid ratio is further increased (the total amount of *Chlamydomonas reinhardtii* further increases), for example to 1:100, that is, 10 g of *Sargassum fusiforme* is incubated in 1000 mL of 1% *Chlamydomonas reinhardtii* suspension, its iodine removal effect may become even stronger because the total amount of *Chlamydomonas reinhardtii* contained in it further increases to 10 g (the mass ratio of *Sargassum fusiforme* to *Chlamydomonas reinhardtii* reaches 1:1). However, if the total amount of *Chlamydomonas reinhardtii* increases excessively, meaning that the proportion of *Chlamydomonas reinhardtii* in the mass ratio of *Sargassum fusiforme* to *Chlamydomonas reinhardtii* is too high, the cost will increase unacceptably due to the excessive amount of *Chlamydomonas reinhardtii* used. Of course, if the solid-liquid ratio is too high, the water consumption and post-treatment workload will increase, and the cost will also increase significantly. Therefore, within the acceptable range of total *Chlamydomonas reinhardtii* usage, increasing the concentration of *Chlamydomonas reinhardtii* and reducing the suspension volume may be a good choice. For example, under the same conditions, if 10 g of *Sargassum fusiforme* is incubated with 50 mL of a 20% *Chlamydomonas reinhardtii* suspension at a solid-liquid ratio of 1:5, the total amount of *Chlamydomonas reinhardtii* will also increase to 10 g, and the mass ratio of *Sargassum fusiforme* to *Chlamydomonas reinhardtii* will reach 1:1. The increased total amount of *Chlamydomonas reinhardtii* will correspondingly enhance its deiodination effect, while overcoming the drawbacks of excessive water consumption at a solid-liquid ratio of 1:100. This also shows that the concentration of Chlamydomonas reinhardtii and the solid-liquid ratio are good engineering parameters that can be used to achieve the desired iodine removal effect by adjusting the total amount of Chlamydomonas reinhardtii and the amount of water used.

[0073] The above experimental results show that, using the same concentration of *Chlamydomonas reinhardtii* tap water suspension, adding the same amount of *Sargassum fusiforme* to different volumes of *Chlamydomonas reinhardtii* suspension at different solid-liquid ratios (i.e., incubating *Sargassum fusiforme* and *Chlamydomonas reinhardtii* in different volumes of tap water at different mass ratios), under the same incubation conditions for the same time, the adsorption and deiodination effect of *Chlamydomonas reinhardtii* increases with the increase of the solid-liquid ratio. The experimental results are consistent with the increase in the total amount of *Chlamydomonas reinhardtii* in each group. Based on the above experimental results, the insights gained, and the research results of Examples 1-3, when using *Chlamydomonas reinhardtii* to deiodize *Sargassum fusiforme* through incubation in tap water, the total amount of *Chlamydomonas reinhardtii* in the suspension and the amount of water used can be controlled by changing the *Chlamydomonas reinhardtii* concentration and solid-liquid ratio to obtain the expected deiodination effect. Once the *Chlamydomonas reinhardtii* concentration and solid-liquid ratio are determined, the mass ratio of *Sargassum fusiforme* to *Chlamydomonas reinhardtii* is also determined. Optionally, the *Chlamydomonas reinhardtii* concentration can be 0.1-20%, and the solid-liquid ratio can be... The mass ratio of Sargassum fusiforme to Chlamydomonas reinhardtii is 1:0.05-1:1, preferably 0.5-20% concentration of Chlamydomonas reinhardtii, 1:2.5-1:50 solid-liquid ratio of Sargassum fusiforme to Chlamydomonas reinhardtii, and 1:0.1-1:0.5 mass ratio of Sargassum fusiforme to Chlamydomonas reinhardtii. More preferably 10-20% concentration of Chlamydomonas reinhardtii, 1:2.5-1:5 solid-liquid ratio of Sargassum fusiforme to Chlamydomonas reinhardtii, and 1:0.2-1:0.5 mass ratio of Sargassum fusiforme to Chlamydomonas reinhardtii.

[0074] Example 4: Investigating the effect of solid-liquid ratio of Sargassum fusiforme and Chlamydomonas reinhardtii suspensions in tap water of different concentrations on the iodine removal process of Chlamydomonas reinhardtii. In this embodiment, Sargassum fusiforme was used as the subject. Equal amounts of Sargassum fusiforme samples were placed in tap water suspensions of Chlamydomonas reinhardtii at different solid-liquid ratios and incubated at room temperature (25°C) and 200 rpm for 120 min. The iodine content in Sargassum fusiforme was then measured to investigate the effect of solid-liquid ratio on the deiodination of Chlamydomonas reinhardtii.

[0075] (1) Incubation treatment of Sargassum fusiforme in tap water with different solid-liquid ratios and different concentrations of Chlamydomonas reinhardtii. Eight 250 mL and two 500 mL Erlenmeyer flasks were taken and divided into two groups of five, each group consisting of four 250 mL flasks and one 500 mL flask. In one group of five Erlenmeyer flasks, 50, 100, 150, 200, and 500 mL of tap water were added respectively to serve as the solid-liquid ratio control (tap water group) at ratios of 1:5, 1:10, 1:15, 1:20, and 1:50. In the other group of five Erlenmeyer flasks, 5.0 g of *Chlamydomonas reinhardtii* (weighed to an accuracy of 0.001 g) was added to each flask, and then 50, 100, 150, 200, and 500 mL of tap water were added respectively. These were then used as the solid-liquid ratio incubation treatment groups at ratios of 1:5, 1:10, 1:15, 1:20, and 1:50, with *Chlamydomonas reinhardtii* concentrations of 10%, 5%, 3.33%, 2.5%, and 1%, respectively. Take an appropriate amount of fresh Sargassum fusiforme from a 4°C refrigerator, wash off any impurities adhering to the surface of the thallus with tap water, and then wipe off the surface moisture with absorbent paper. Weigh out 10 samples, each approximately 10 g, and add one sample to each of the 10 Erlenmeyer flasks. Load the 10 Erlenmeyer flasks onto a shaker fixture and incubate at 25°C and 200 rpm for 120 min. Stop shaking the shaker to terminate the incubation. The sampling and subsequent processing procedures after incubation are the same as in Example 1.

[0076] (2) Determination of iodine content in Sargassum fusiforme samples The methods for determining iodine content and processing data are exactly the same as those in Example 1 above.

[0077] (3) Experimental results The iodine content in the untreated group of Sargassum fusiforme, as well as the iodine content, deiodination rate, and iodine removal rate of each incubation group obtained by incubation in tap water and tap water suspensions of Chlamydomonas reinhardtii at different solid-liquid ratios for 120 min, are shown in Table 4.

[0078] Table 4. Iodine content, iodine removal rate, and iodine removal rate of Chlamydomonas reinhardtii samples in each group.

[0079] As shown in Table 4, 1) Compared with the untreated group, the iodine content of the tap water control group with different solid-liquid ratios did not decrease significantly, and the iodine removal rate was below 5.7%, indicating that the results are consistent with those in Examples 1-3, and that shaking treatment in tap water has no significant iodine removal effect on the iodine contained in Sargassum fusiforme; 2) Compared with the untreated group, the iodine content of the tap water incubation group with different solid-liquid ratios was significantly reduced, and was significantly lower than that of the tap water control group with different solid-liquid ratios. However, the iodine removal rate of the tap water group with different solid-liquid ratios was significantly higher than that of the tap water control group with the same solid-liquid ratio, indicating that Chlamydomonas fusiforme showed a significant adsorption and iodine removal effect in different solid-liquid ratio experiments; 3) Looking at the inter-group changes in the Chlamydomonas reinhardtii tap water data for each solid-liquid ratio, the iodine content, deiodination rate, and Chlamydomonas reinhardtii iodine removal rate did not show a regular change with the solid-liquid ratio, and the changes were not significant. The deiodination rate fluctuated very little around 54%, indicating that the deiodination effect of each group was basically the same. The iodine removal rate of Chlamydomonas reinhardtii in each group was close to 50%, and the changes were also very small, indicating that the iodine removal effect of Chlamydomonas reinhardtii in each group was also basically the same.

[0080] In this example, each group of tested Sargassum fusiforme consisted of 10 g of Sargassum fusiforme. Although the solution volume of each Chlamydomonas reinhardtii group increased with the increase of the solid-liquid ratio, and the concentration decreased with the increase of the solid-liquid ratio, the total amount of Chlamydomonas reinhardtii in each group was the same, which was 5 g (Sargassum fusiforme to Chlamydomonas reinhardtii mass ratio 1:0.5). This suggests that the iodine removal effect and the strength of the iodine removal effect of Chlamydomonas reinhardtii seem to be directly related only to the total amount of Chlamydomonas reinhardtii in each group, and not directly related to the change in solid-liquid ratio or concentration. These experimental results also show that by incubating with a small volume of high-concentration Chlamydomonas reinhardtii suspension, a similar iodine removal effect as that of incubating with a large volume of low-concentration Chlamydomonas reinhardtii suspension has been obtained. This also suggests that if 10 g of Sargassum fusiforme is incubated with 25 mL of 20% Chlamydomonas reinhardtii tap water suspension (i.e., at a Sargassum fusiforme to Chlamydomonas reinhardtii mass ratio of 1:0.5) at room temperature (25°C) and shaken on a shaker at 200 rpm for 120 min, it is entirely possible to obtain a similar iodine removal effect as described above.

[0081] The above experimental results indicate that when Sargassum fusiforme is placed in tap water suspensions of Chlamydomonas reinhardtii at different solid-liquid ratios and incubated for the same period under the same conditions, the strength and effectiveness of iodine removal by Chlamydomonas reinhardtii appear to be related only to the total amount of Chlamydomonas reinhardtii in the suspension, and not to changes in the solid-liquid ratio or concentration. This embodiment achieved a similar iodine removal effect to that obtained by incubating with a small volume of high-concentration Chlamydomonas reinhardtii suspension as by incubating with a large volume of low-concentration Chlamydomonas reinhardtii suspension. This has significant practical value for industrial applications, as using a small volume of high-concentration Chlamydomonas reinhardtii suspension for incubation will save considerable water resources and correspondingly reduce costs.

[0082] Based on the research results of this embodiment and Examples 1-3 above, when using *Chlamydomonas reinhardtii* to incubate *Sargassum fusiforme* in tap water to remove iodine from *Sargassum fusiforme*, the total amount of *Chlamydomonas reinhardtii* and the amount of water in the suspension can be controlled by changing the concentration of *Chlamydomonas reinhardtii* and the solid-liquid ratio, thereby obtaining the expected iodine removal effect. Optionally, the concentration of *Chlamydomonas reinhardtii* can be 0.1-20%, and the solid-liquid ratio can be 1:2.5-1:100; preferably, the concentration of *Chlamydomonas reinhardtii* is 0.5-20%, and the solid-liquid ratio is 1:2.5-1:50; more preferably, the concentration of *Chlamydomonas reinhardtii* is 10-20%, and the solid-liquid ratio is 1:2.5-1:5.

[0083] Example 5: Investigation of the effects of Chlamydomonas reinhardtii concentration and incubation time on iodine content in kelp This embodiment uses kelp as the subject. After incubating kelp with different concentrations of Chlamydomonas reinhardtii for different times in tap water, the iodine content in the kelp was measured to examine the effects of concentration and time on the iodine removal process of Chlamydomonas reinhardtii.

[0084] (1) Treatment of kelp with different concentrations of Chlamydomonas reinhardtii in tap water The incubation treatment experiment on kelp was designed with five groups incubation periods: a control group (tap water) and groups treated with 0.1%, 0.5%, 1%, and 2% *Chlamydomonas reinhardtii* in tap water, for 60 min, 120 min, and 180 min respectively. A total of 15 experimental groups were set up, using 15 500 mL Erlenmeyer flasks, divided into five groups of three. The solution volume for each control group and each concentration of *Chlamydomonas reinhardtii* was 500 mL. The total amount of *Chlamydomonas reinhardtii* in the 0.1%, 0.5%, 1%, and 2% groups was 0.5, 2.5, 5.0, and 10.0 g, respectively. Each group consisted of 15 fresh kelp samples, approximately 10 g each. Take an appropriate amount of fresh kelp from a 4°C refrigerator, wash off any impurities adhering to the surface of the kelp with tap water, and then wipe off the surface moisture with absorbent paper. Weigh out 15 kelp samples, each approximately 10 g, and add them to 15 Erlenmeyer flasks, one sample per flask. Then, load all 15 Erlenmeyer flasks onto a shaker fixture and incubate them at room temperature (25°C) and 200 rpm. The sampling and subsequent processing after incubation are the same as in Example 1.

[0085] (2) Determination of iodine content in kelp samples The methods for determining iodine content and processing data are exactly the same as those in Example 1 above.

[0086] (3) Experimental results The iodine content in the untreated kelp group and the iodine content, deiodination rate, and iodine removal rate of each group of kelp treated with different concentrations of Chlamydomonas reinhardtii in tap water, as measured by the above experiments, are shown in Table 5.

[0087] Table 5. Iodine content, iodine removal rate, and Chlamydomonas reinhardtii iodine removal rate in kelp samples of each group.

[0088] Table 5 shows that: 1) Compared with the untreated group, the iodine content in kelp in each solvent control tap water group decreased significantly with increasing incubation time, while the iodine removal rate increased accordingly. Furthermore, the iodine removal rate reached approximately 74% after 180 min of incubation, indicating that unlike the experimental results for Sargassum fusiforme in Examples 1-4, for kelp, as long as the water volume is sufficient and the treatment time is long enough, shaking treatment in tap water will achieve a significant iodine removal effect; 2) Comparing the data of each concentration of Chlamydomonas reinhardtii group with the solvent control tap water group at the same incubation time, the iodine content decreased significantly, while the iodine removal rate increased significantly. This difference was particularly significant in the 60 min incubation group, while in the 180 min group, this difference seemed insignificant due to the already high iodine removal rate in the tap water group; 3) The iodine content, deiodization rate, and iodine removal rate of *Chlamydomonas reinhardtii* in tap water groups with different concentrations did not show a linear decrease or increase with increasing *Chlamydomonas reinhardtii* concentration among groups with the same incubation time. As mentioned earlier, because the solution volume was the same in each group, the total amount of *Chlamydomonas reinhardtii* in each group increased with increasing concentration, indicating that iodine content, deiodization rate, and iodine removal rate did not show a linear correlation with changes in the total amount of *Chlamydomonas reinhardtii*. Overall, among the various concentrations of *Chlamydomonas reinhardtii*, the 0.5% *Chlamydomonas reinhardtii* group showed the best iodine removal effect; 4) The iodine removal rate of *Chlamydomonas reinhardtii* in tap water groups of various concentrations showed a regular change among groups with different incubation times at the same concentration, that is, the iodine removal rate of *Chlamydomonas reinhardtii* decreased significantly with the increase of incubation time, indicating that the contribution of *Chlamydomonas reinhardtii* to iodine removal in each group was the largest at 60 min of incubation and the smallest at 180 min; that is, at the incubation treatment time of 180 min, the contribution of *Chlamydomonas reinhardtii* to iodine removal had become very small, and the iodine removal rate of *Chlamydomonas reinhardtii* was even lower than that of the solvent control tap water group at 60 min. However, as the incubation time decreased, the contribution of *Chlamydomonas reinhardtii* to iodine removal, i.e., the iodine removal rate of *Chlamydomonas reinhardtii*, increased significantly in the 120 min and 60 min incubation groups. Based on the iodine removal rate data, the 0.5% *Chlamydomonas reinhardtii* group not only had the largest contribution to adsorption and iodine removal, i.e., the iodine removal rate of *Chlamydomonas reinhardtii*, but also the best iodine removal effect, maintaining an iodine removal rate of 93-95%, reaching over 93% at 60 min of incubation. Although the effects of other concentrations of *Chlamydomonas reinhardtii* were not as good as the 0.5% group, the experimental results and data showed the same trend.

[0089] These results indicate that incubating kelp in tap water with Chlamydomonas reinhardtii can significantly shorten the incubation time required for iodine removal from kelp. The concentration of Chlamydomonas reinhardtii can be 0.1%-20%, preferably 0.1%-5%, more preferably 0.1%-1%, and most preferably 0.1%-0.5%. The incubation time can be 10 min-200 min, preferably 20 min-180 min, more preferably 30 min-120 min, and most preferably 60 min-120 min.

[0090] The above experimental results show that incubating kelp with Chlamydomonas reinhardtii in tap water can remove iodine from kelp, significantly shorten the incubation time required for iodine removal, and achieve better and more efficient iodine removal without increasing water usage.

[0091] Example 6: Investigation of the effects of Chlamydomonas reinhardtii concentration and incubation time on the iodine content of Undaria pinnatifida This embodiment uses wakame seaweed as the subject. After incubating it in tap water with different concentrations of Chlamydomonas reinhardtii for different times, the iodine content in wakame seaweed was measured to examine the effects of concentration and time on the iodine removal process of Chlamydomonas reinhardtii.

[0092] (1) Treatment of Wakame seaweed with different concentrations of Chlamydomonas reinhardtii in tap water The incubation experiment on *Wakame seaweed* was designed with five groups incubated for 60 min, 120 min, and 180 min respectively: a control group (tap water) and groups treated with 0.1%, 0.5%, 1%, and 2% *Chlamydomonas reinhardtii* in tap water. A total of 15 experimental groups were set up, using 15 500 mL Erlenmeyer flasks, divided into five groups of three. The solution volume for each control group and each concentration of *Chlamydomonas reinhardtii* in tap water was 500 mL. The total amount of *Chlamydomonas reinhardtii* in the 0.1%, 0.5%, 1%, and 2% groups was 0.5, 2.5, 5.0, and 10.0 g, respectively. A suitable amount of fresh *Wakame seaweed* was taken from a 4℃ refrigerator, washed with tap water to remove impurities, and then wiped dry with absorbent paper. Fifteen samples of approximately 10 g each were weighed and added to the 15 Erlenmeyer flasks, one sample per flask. Subsequently, all 15 Erlenmeyer flasks were loaded onto the shaker plate fixture and incubated at room temperature (25 °C) and 200 rpm. The sampling and subsequent processing were the same as in Example 1.

[0093] (2) Determination of iodine content in wakame seaweed samples The methods for determining iodine content and processing data are exactly the same as those in Example 1 above.

[0094] (3) Experimental results The iodine content in the untreated group of wakame seaweed and the iodine content, deiodination rate and iodine removal rate of each group of wakame seaweed treated with different concentrations of Chlamydomonas reinhardtii in tap water, as measured by the above experiments, are shown in Table 6.

[0095] Table 6. Iodine content, iodine removal rate, and iodine removal rate of *Chlamydomonas reinhardtii* in each group of *Wakame* samples.

[0096] Table 6 shows that: 1) Compared with the untreated group, the iodine content in the tap water group (solvent control) decreased with increasing incubation time, while the iodine removal rate increased accordingly. However, the iodine content was still below 6.5% at 60 min and 120 min, but reached 12.21% at 180 min. This indicates that for wakame, shaking treatment in tap water has no significant iodine removal effect when the treatment time is less than 120 min, similar to the results of Examples 1-4, but shows a certain iodine removal effect at 180 min; 2) From the overall change in iodine removal rate among the groups, compared with the tap water group (solvent control), the 0.1% Chlamydomonas reinhardtii group showed almost no additional significant iodine removal effect, while the iodine removal effect of the 0.5% and above concentration Chlamydomonas reinhardtii groups showed a significant improvement with increasing concentration, as evidenced by the iodine removal rate data; 3) From the data changes within each group of *Chlamydomonas reinhardtii*, the iodine removal rate of the 0.5% and 1% *Chlamydomonas reinhardtii* groups increased with increasing incubation time, indicating that the longer the incubation time in these two groups, the better the iodine removal effect. However, the iodine removal rate of the 2% *Chlamydomonas reinhardtii* group reached its highest peak of 58.72% at 120 min incubation time, and then slightly decreased at 180 min, indicating that the iodine removal effect of this group was best at 120 min incubation. In addition, the iodine removal rate of *Chlamydomonas reinhardtii* in each group also showed a corresponding change that was completely consistent with this, and accounted for the vast majority of the iodine removal rate in each group, indicating that the iodine removal effect in each group mainly came from the adsorption and iodine removal contribution of *Chlamydomonas reinhardtii*. 4) The data changes of the 60 min and 120 min incubation groups of each concentration of *Chlamydomonas reinhardtii* showed a clear dependence on the concentration (total) of *Chlamydomonas reinhardtii*, that is, as the concentration (total) of *Chlamydomonas reinhardtii* increased, the iodine content decreased while the iodine removal rate and the iodine removal rate of *Chlamydomonas reinhardtii* increased. This change is also consistent with the fact that the total amount of *Chlamydomonas reinhardtii* in the 0.1%, 0.5%, 1%, and 2% concentration groups increased to 0.5, 2.5, 5, and 10 g respectively. In the group treated for 180 min, although the data of each group did not show a concentration-dependent change, the iodine removal rate of each concentration of *Chlamydomonas reinhardtii* above 0.5% reached more than 50%. Although this included a large contribution from solvent immersion for iodine removal, the overall iodine removal effect was still very good.

[0097] In summary, when using *Chlamydomonas reinhardtii* to incubate and deiodize *Undaria pinnatifida*, the concentration of *Chlamydomonas reinhardtii* can be 0.1%-5%, preferably 0.5%-2%, and more preferably 1%-2%. The incubation time can be 60 min-200 min, preferably 120 min-180 min. The combination of *Chlamydomonas reinhardtii* concentration and incubation time can be between a concentration of 0.5-2% and a time of 120-180 min. Preferably, the incubation time is 180 min when the *Chlamydomonas reinhardtii* concentration is 0.5% or 1%, and more preferably, the incubation time is 120 min when the *Chlamydomonas reinhardtii* concentration is 2%.

[0098] The above experimental results show that incubating wakame seaweed with Chlamydomonas reinhardtii in tap water can remove iodine from wakame seaweed. Under the same conditions, the iodine removal effect is related to the concentration of Chlamydomonas reinhardtii and the incubation time. The iodine removal effect is better when the concentration is 0.5-2% and the incubation time is 120-180 min. Preferably, the incubation time is 180 min when the concentration is 0.5% or 1%, and more preferably, the incubation time is 120 min when the concentration is 2%.

[0099] Example 7: Investigation on the effects of Chlamydomonas reinhardtii concentration and incubation time on the iodine content of Porphyra yezoensis This embodiment uses *Porphyra yezoensis* as the subject. After incubating *Chlamydomonas reinhardtii* with different concentrations in tap water for different times, the iodine content in *Porphyra yezoensis* was measured to examine the effects of concentration and time on the iodine removal process of *Chlamydomonas reinhardtii*.

[0100] (1) Treatment of different concentrations of Chlamydomonas reinhardtii in tap water for the incubation of Porphyra yezoensis The incubation treatment experiment on *Porphyra yezoensis* was designed with five groups: a control group (tap water) and groups treated with 0.1%, 0.5%, 1%, and 2% *Chlamydomonas reinhardtii* in tap water, incubated for 60 min, 120 min, and 180 min respectively. A total of 15 experimental groups were set up, using 15 500 mL Erlenmeyer flasks, divided into five groups of three. The solution volume for each control group (tap water) and each concentration of *Chlamydomonas reinhardtii* was 500 mL. The total amount of *Chlamydomonas reinhardtii* in the 0.1%, 0.5%, 1%, and 2% groups was 0.5, 2.5, 5.0, and 10.0 g, respectively. Each group's incubation treatment sample consisted of 15 aliquots of dried *Porphyra yezoensis*, each 10 g (accurate to 0.01 g). Take an appropriate amount of dried laver sample from the room temperature storage room, weigh out 15 portions of laver sample, each 10 g (accurate to 0.01 g), and add them to 15 Erlenmeyer flasks, one portion per flask. Then, load all 15 Erlenmeyer flasks onto a shaker clamp and incubate them at room temperature (25 ℃) and 200 rpm.

[0101] Post-incubation processing: For the solvent control group (tap water group), *Porphyra yezoensis* was filtered through four layers of gauze. After squeezing out the water by tightening the gauze, it was spread evenly on a 9 cm glass petri dish. For the *Chlamydomonas reinhardtii* (tap water group) at various concentrations, the suspension was poured through a 20-mesh sieve to remove *Chlamydomonas reinhardtii*, and the filtered *Porphyra yezoensis* was poured into 500 mL of tap water. After a brief stirring to remove any attached *Chlamydomonas reinhardtii*, it was immediately poured through a 20-mesh sieve to remove the *Chlamydomonas reinhardtii*. This washing process was repeated three times. The *Porphyra yezoensis* was squeezed through the sieve to remove water and then spread evenly on a 9 cm glass petri dish. The *Porphyra yezoensis* samples on each petri dish were dried in an oven at 80℃ for 24 h until constant weight was achieved.

[0102] The untreated group samples were dried laver samples stored at room temperature without incubation. An appropriate amount of the dried laver sample was taken out, spread on a 9 cm glass petri dish, and dried in an oven at 80℃ for 24 h until constant weight was achieved, for the determination of iodine content.

[0103] (2) Determination of iodine content in laver samples The samples were dried laver samples from the untreated group and each treated group, dried to constant weight. 2.0 g of each sample (accurate to 0.01 g) was weighed, and the iodine content was determined. The iodine content determination and data processing methods were exactly the same as in Example 1 above.

[0104] (3) Experimental results The iodine content in the untreated dried laver samples and the iodine content, deiodination rate, and Chlamydomonas rindis iodine removal rate of each group of dried laver samples treated with different concentrations of Chlamydomonas rindis in tap water are shown in Table 7.

[0105] Table 7. Iodine content, iodine removal rate, and iodine removal rate of Chlamydomonas reinhardtii in each group of dried seaweed samples.

[0106] Table 7 shows that: 1) Compared with the untreated group, the iodine content in *Porphyra yezoensis* in each solvent control tap water group did not decrease significantly, and the iodine removal rate was below 5.7%, indicating that the results were the same as those of *Sargassum fusiforme* in Examples 1-4, and that shaking treatment of *Porphyra yezoensis* in tap water did not have a significant effect on removing iodine; 2) Compared with the untreated group, except for the 0.1% *Chlamydomonas reinhardtii* incubation group for 60 min, the iodine content in *Porphyra yezoensis* in tap water groups of all other concentrations decreased significantly; compared with the solvent control tap water group, except for the 0.1% *Chlamydomonas reinhardtii* 60 min group, the iodine removal rate of all other *Chlamydomonas reinhardtii* groups increased significantly; from the data changes of the *Chlamydomonas reinhardtii* tap water groups of each concentration under the same incubation time, it can be seen that the overall iodine removal effect increases with the increase of *Chlamydomonas reinhardtii* concentration (total); 3) Data from tap water groups with different concentrations of *Chlamydomonas reinhardtii* showed a clear time-dependent change. Iodine content decreased with increasing incubation time, while the iodine removal rate increased, generally indicating that longer incubation times resulted in better iodine removal. The changes in the iodine removal rate of *Chlamydomonas reinhardtii* in each group also corresponded to this, with over 94% of the iodine removal rate attributable to *Chlamydomonas reinhardtii*, suggesting that the iodine removal effect was primarily due to the adsorption and removal contribution of *Chlamydomonas reinhardtii*. 4) Data changes among tap water groups with the same incubation time for different concentrations of *Chlamydomonas reinhardtii* generally showed a concentration-dependent change, i.e., as the concentration of *Chlamydomonas reinhardtii* increased, iodine content decreased while the iodine removal rate and the iodine removal rate of *Chlamydomonas reinhardtii* increased. However, in the 180-min incubation group, the data from the 1% and 2% *Chlamydomonas reinhardtii* tap water groups did not show a concentration-dependent change; the iodine content, iodine removal rate, and *Chlamydomonas reinhardtii* iodine removal rate were essentially the same in both groups. This may be because when the incubation time reaches more than 180 min, the adsorption of iodine-containing substances by Chlamydomonas reinhardtii at a concentration of more than 1% may have reached a saturation point, that is, the adsorption and desorption of iodine-containing substances have reached an equilibrium state where the adsorption amount can no longer be increased.

[0107] In summary, when using Chlamydomonas reinhardtii to incubate and deiodize Porphyra yezoensis, the concentration of Chlamydomonas reinhardtii can be 0.1%-2%, preferably 0.5%-2%, and more preferably 1%-2%. The incubation time can be 60 min-180 min, preferably 120 min-180 min, and more preferably 180 min.

[0108] The above experimental results show that incubating Porphyra yezoensis in tap water with Chlamydomonas reinhardtii can remove iodine from Porphyra yezoensis. Under the same conditions, the iodine removal effect is related to the concentration of Chlamydomonas reinhardtii and the incubation time. Therefore, better iodine removal effect can be achieved by selecting the optimal concentration of Chlamydomonas reinhardtii and the optimal incubation time.

[0109] Example 8: Effect of incubation temperature on iodine removal efficiency of *Chlamydomonas reinhardtii* in *Sargassum fusiforme* and an empirical investigation of the biosorption and deiodination effect of *Chlamydomonas reinhardtii*. This embodiment uses Sargassum fusiforme as the subject and tap water as the medium. Two concentrations and two volumes of Chlamydomonas reinhardtii tap water suspensions were used. Equal amounts of Sargassum fusiforme were placed in the same concentration and volume of Chlamydomonas reinhardtii suspensions and incubated for the same time at different temperatures and rotation speeds. The iodine content in the Sargassum fusiforme was then measured to examine the effect of incubation temperature on the deiodination of Chlamydomonas reinhardtii. At the same time, after the Sargassum fusiforme was removed, each Chlamydomonas reinhardtii suspension was centrifuged to separate the supernatant and the Chlamydomonas reinhardtii algae. The iodine content in the algae and the supernatant was measured separately. The experiment confirmed the bio-adsorption deiodination effect of Chlamydomonas reinhardtii.

[0110] (1) Treatment of Sargassum fusiforme with Chlamydomonas reinhardtii at different temperatures The incubation treatment of *Chlamydomonas reinhardtii* in Sargassum fusiforme at different temperatures involved 10 g of Sargassum fusiforme in each group. Two methods were employed: incubation with 50 mL of 5% *Chlamydomonas reinhardtii* tap water suspension for 60 min and incubation with 500 mL of 1% *Chlamydomonas reinhardtii* tap water suspension for 120 min. Incubation was performed on a shaker at 200 rpm at 15℃, 25℃, and 30℃, respectively. A corresponding control group (tap water) was also set up to investigate the effect of incubation temperature on the deiodination of *Chlamydomonas reinhardtii* in Sargassum fusiforme.

[0111] 1.1 Experiment on incubation treatment of 5% Chlamydomonas reinhardtii suspension in tap water for 60 min: Take six 250 mL Erlenmeyer flasks. Add 50 mL of tap water to three of them to serve as the solvent control group (tap water group) for incubation at 15℃, 25℃, and 30℃, respectively. Add 2.5 g (accurate to 0.001 g) of Chlamydomonas reinhardtii to each of the other three Erlenmeyer flasks, then add 50 mL of tap water to each, shake well, and prepare a 5% Chlamydomonas reinhardtii suspension. Used as the Chlamydomonas reinhardtii incubation treatment group for incubation at 15℃, 25℃, and 30℃, respectively. Take fresh Sargassum fusiforme from a 4℃ refrigerator, rinse the surface of Sargassum fusiforme with tap water to remove impurities, wipe the surface dry with absorbent paper, weigh out 6 portions of 10 g each, and add one portion to each of the above six Erlenmeyer flasks. Subsequently, the six Erlenmeyer flasks were divided into three groups of two: one group containing a solvent control and tap water, and one group containing Chlamydomonas reinhardtii and tap water. The two Erlenmeyer flasks in each group were placed on shakers at 15°C, 25°C, and 30°C, respectively, and incubated at 200 rpm for 60 minutes. Shaking was then stopped to terminate the incubation. The Erlenmeyer flasks were removed, and the following follow-up treatments were immediately performed. For the solvent control group (tap water), after removing the Sargassum fusiforme from the Erlenmeyer flasks, the surface moisture was wiped dry with absorbent paper. Approximately 10 g (accurate to 0.001 g) of each sample was weighed and placed in a 50 mL crucible for the following experiment to determine the iodine content. After the *Sargassum fusiforme* (5% *Chlamydomonas reinhardtii*) in the tap water group was removed from the *Chlamydomonas reinhardtii* suspension, the surface of the *Chlamydomonas reinhardtii* was quickly rinsed with tap water, and then the surface moisture was wiped off with absorbent paper. Approximately 10 g (accurate to 0.001 g) of each group was weighed and placed in a 50 mL crucible for the following experiments to determine the iodine content. The *Chlamydomonas reinhardtii* suspension after removing the *Sargassum fusiforme* was centrifuged at 4200 rpm for 10 min, and the supernatant and *Chlamydomonas reinhardtii* cells were separated. 100 mL of the supernatant from each group was directly used for the following experiments to determine the iodine content, while the *Chlamydomonas reinhardtii* cells from each group were dried in a 60℃ oven for 48 h until constant weight was achieved. 2-4 g (accurate to 0.001 g) of each group was weighed and placed in a 50 mL crucible for the following experiments to determine the iodine content.

[0112] 1.2 Experiment on incubation of 1% Chlamydomonas reinhardtii suspension in tap water for 120 min: Six 500 mL Erlenmeyer flasks were used. Three flasks were each incubated with 500 mL of tap water, serving as the control group (tap water group) for incubation at 15℃, 25℃, and 30℃, respectively. The other three flasks were each incubated with 5.0 g (accurate to 0.001 g) of Chlamydomonas reinhardtii, followed by 500 mL of tap water. The mixture was shaken well to prepare a 1% Chlamydomonas reinhardtii suspension, which was used as the incubation treatment group for incubation at 15℃, 25℃, and 30℃, respectively. Fresh Sargassum fusiforme was removed from a 4℃ refrigerator, rinsed with tap water to remove surface impurities, and wiped dry with absorbent paper. Six 10 g portions were weighed and added to the six Erlenmeyer flasks, one portion per flask. Subsequently, the six Erlenmeyer flasks were divided into three groups of two, including one group containing tap water as a solvent control and one group containing tap water containing *Chlamydomonas reinhardtii*. The two Erlenmeyer flasks in each group were placed on shakers at 15°C, 25°C, and 30°C, respectively, and incubated at 200 rpm for 120 min. Shaking was then stopped to terminate the incubation. The Erlenmeyer flasks were removed, and the following follow-up treatments were immediately performed. The follow-up treatment for each group of samples in the experiment with 500 mL of 1% *Chlamydomonas reinhardtii* tap water suspension for 120 min was the same as that in the experiment with 50 mL of 5% *Chlamydomonas reinhardtii* tap water suspension for 60 min.

[0113] (2) Determination of iodine content in Sargassum fusiforme and Chlamydomonas reinhardtii samples The untreated Sargassum fusiforme samples were fresh Sargassum fusiforme samples stored in a 4°C refrigerator without any incubation treatment. After being taken out of the refrigerator, the surface moisture was wiped off with absorbent paper, and about 10 g (accurate to 0.001 g) was weighed to determine the iodine content.

[0114] The untreated Chlamydomonas reinhardtii samples were Chlamydomonas reinhardtii samples stored in a room temperature warehouse that had not been used for incubation treatment. An appropriate amount was taken out of the warehouse and dried in a 60℃ oven for 48 h. After drying to constant weight, 2.585 g was weighed to determine the iodine content.

[0115] 100 mL of the supernatant from each Chlamydomonas reinhardtii group was taken and placed in an iodine flask for direct use in the redox titration experiment for iodine content determination.

[0116] The methods for determining iodine content and processing data are exactly the same as those in Example 1 above.

[0117] It should be noted that when the crucibles containing Sargassum fusiforme and Chlamydomonas reinhardtii samples were placed in a muffle furnace and calcined at 550°C for 40 min, and the furnace temperature was cooled to room temperature before the crucibles were removed, the calcination residue of Sargassum fusiforme was pure white, grayish-white, or gray, i.e., a mixture of pure white residue, grayish-white residue, and gray residue, while the calcination residue of Chlamydomonas reinhardtii was all black.

[0118] (3) Experimental results The iodine content in the untreated group of Sargassum fusiforme, the iodine content, deiodination rate, and iodine removal rate of each group of Sargassum fusiforme treated with different concentrations of Chlamydomonas reinhardtii in tap water are shown in Table 8; the iodine content in each group of Chlamydomonas reinhardtii thallus and the iodine detection results in the supernatant of the Chlamydomonas reinhardtii suspension centrifuged are shown in Table 9.

[0119] Table 8. Iodine content, iodine removal rate and iodine removal rate of Chlamydomonas reinhardtii in each group of Sargassum fusiforme

[0120] Table 8 shows that: 1) Compared with the untreated group, the iodine content in each water group did not decrease significantly. The iodine removal rate in the 60-minute incubation group was below 3.5%, and the iodine removal rate in the 120-minute incubation group was less than 5.5%, indicating that, consistent with the results in Examples 1-4, shaking treatment of tap water at different temperatures did not have a significant effect on removing iodine from Sargassum fusiforme; 2) From the data changes of the Chlamydomonas reinhardtii incubation treatment groups at various concentrations for 60 or 120 minutes, the iodine content in Sargassum fusiforme decreased to its lowest point at 25℃, while the iodine removal rate and the iodine removal rate of Chlamydomonas reinhardtii reached their highest points at 25℃. From the changes in iodine content or iodine removal rate in each group, the iodine removal effect was best at 25℃, followed by 15℃, and then 30℃. The changes in iodine removal rate of *Chlamydomonas reinhardtii* also corresponded to this, indicating that the contribution of *Chlamydomonas reinhardtii* to iodine removal was greatest at 25℃, followed by 15℃, and then again at 30℃. These results suggest that when using *Chlamydomonas reinhardtii* to remove iodine from *Sargassum fusiforme*, incubation treatment at 25℃ or 20-25℃ is recommended.

[0121] Table 9. Iodine content in Chlamydomonas reinhardtii thallus and iodine detection results in the supernatant of Chlamydomonas reinhardtii suspension in each group.

[0122] As shown in Table 9, no iodine was detected in the supernatant of *Chlamydomonas reinhardtii* in the untreated group and in each treated group, while iodine was detected in the *Chlamydomonas reinhardtii* cells in each treated group. Furthermore, the iodine content in *Chlamydomonas reinhardtii* reached its peak at an incubation temperature of 25℃ in both the 60-min and 120-min incubation groups. The iodine content decreased with temperature, with the highest concentration at 25℃, followed by 15℃, and then again at 30℃. This result is completely consistent with the changes in iodine removal rate in *Sargassum fusiforme* and the iodine removal rate in *Chlamydomonas reinhardtii* observed in Table 8. This undoubtedly provides substantial experimental evidence for the biosorption and iodine removal function of *Chlamydomonas reinhardtii*.

[0123] The above experimental results show that incubating Sargassum fusiforme in tap water with Chlamydomonas reinhardtii can remove iodine from Sargassum fusiforme. Chlamydomonas reinhardtii concentrates iodine on its surface through biosorption of iodine-containing substances, thus exerting its iodine removal effect on Sargassum fusiforme and other large seaweeds. Under the same conditions, the incubation temperature directly affects the iodine removal effect, with the best effect at 25℃, followed by 15℃, and then 30℃. Therefore, when using Chlamydomonas reinhardtii to remove iodine from Sargassum fusiforme and other large seaweeds through incubation in tap water, the incubation temperature can be 15-30℃, with 20-25℃ being preferred, and 25℃ being even more ideal.

[0124] Example 9: Effects of incubation method and stirring rate on iodine removal efficiency of *Chlamydomonas reinhardtii* in *Sargassum fusiforme* and an empirical investigation of the biosorption and deiodination effect of *Chlamydomonas reinhardtii*. This embodiment uses Sargassum fusiforme as the subject and tap water as the medium. Equal amounts of Sargassum fusiforme are placed in Chlamydomonas reinhardtii suspension of the same concentration and volume. Different incubation methods and stirring rates are used. After incubation at the same temperature for the same time, the iodine content in Sargassum fusiforme is measured to examine the effects of incubation method and stirring rate on the deiodination of Chlamydomonas reinhardtii. At the same time, after Sargassum fusiforme is removed, each Chlamydomonas reinhardtii suspension is centrifuged to separate the supernatant and Chlamydomonas reinhardtii thallus. The iodine content in the Chlamydomonas reinhardtii thallus and supernatant is measured respectively. The experiment confirms the bio-adsorption deiodination effect of Chlamydomonas reinhardtii.

[0125] (1) Treatment of Sargassum fusiforme with Chlamydomonas reinhardtii in tap water suspension Take five 100 mL wide-mouth reagent bottles, add 2.5 g of *Chlamydomonas reinhardtii* to each, then add 50 mL of tap water to each, shake well to prepare a 5% *Chlamydomonas reinhardtii* suspension, load them onto a shaker, and pre-incubate at 25℃ and 200 rpm for 12 h for activation. Take fresh *Sargassum fusiforme* from a 4℃ refrigerator, quickly rinse the surface of the *Sargassum fusiforme* with tap water to remove any impurities, wipe the surface dry with absorbent paper, weigh out five portions of 10 g each, and add them to the five reagent bottles mentioned above. Subsequently, incubate at 25℃ for 60 min using one of the following methods: (A) standing, (B) standing with manual stirring for 5 min every 15 min (stirring once before standing and three times within 60 min of standing, for a total of four stirrings), (C) stirring with a magnetic rod at 100 rpm, (D) stirring with a magnetic rod at 150 rpm, and (E) stirring with a magnetic rod at 200 rpm. After the incubation treatment was completed, each group of Sargassum fusiforme was removed from the Chlamydomonas reinhardtii suspension, and the Chlamydomonas reinhardtii adhering to the surface was quickly rinsed with tap water. After wiping the surface with absorbent paper to remove the surface moisture, 10.0 g of each group was weighed and placed in a 50 mL crucible for the following experiments to determine the iodine content.

[0126] After removing Sargassum fusiforme, the Chlamydomonas reinhardtii suspension was centrifuged at 4200 rpm for 10 min to separate the supernatant and Chlamydomonas reinhardtii thallus. The supernatant of each group was directly used for the following experiments to determine the iodine content, while the Chlamydomonas reinhardtii thallus of each group was dried in an oven at 80℃ for 24 h. After drying to constant weight, 2.0 g of each was weighed and placed in a 50 mL crucible for the following experiments to determine the iodine content.

[0127] (2) Determination of iodine content in the sample The untreated Chlamydomonas reinhardtii samples were dried in an oven at 80℃ for 24 h. After drying to constant weight, 2.0 g was weighed to determine the iodine content.

[0128] For the Chlamydomonas reinhardtii group, 100 mL of the centrifuged supernatant was taken and placed in an iodine flask for direct titration.

[0129] The methods for determining iodine content and processing data are exactly the same as those in Example 1 above.

[0130] (3) Experimental results The iodine content in the untreated group of Sargassum fusiforme, the iodine content, deiodination rate, and iodine removal rate of each group of Sargassum fusiforme treated with tap water of the same concentration and volume are shown in Table 10; the iodine content in each group of Chlamydomonas reinhardtii and the iodine detection results in the supernatant of the Chlamydomonas reinhardtii suspension are shown in Table 11.

[0131] Table 10 Iodine content, iodine removal rate and Chlamydomonas lindane removal rate in each group of Sargassum fusiforme

[0132] As shown in Table 10, the iodine content in *Sargassum fusiforme* in each incubation treatment group gradually decreased as the stirring rate increased from zero, while the iodine removal rate correspondingly increased, indicating that the iodine removal effect improved with increasing stirring rate. This also suggests that when using *Chlamydomonas reinhardtii* to remove iodine from *Sargassum fusiforme* through incubation in tap water, thorough stirring during the incubation process is crucial to ensure sufficient contact between the *Chlamydomonas reinhardtii* and *Sargassum fusiforme*, thereby maximizing the adsorption and removal of iodine by the *Chlamydomonas reinhardtii* and achieving a good iodine removal effect.

[0133] Table 11 Iodine content in each group of Chlamydomonas reinhardtii and iodine detection results in the supernatant of Chlamydomonas reinhardtii suspension after centrifugation

[0134] As shown in Table 11, no iodine was detected in the supernatant of *Chlamydomonas reinhardtii* in the untreated group and in the treated groups. However, iodine was detected in the *Chlamydomonas reinhardtii* cells in all treated groups. Furthermore, the iodine content in each group gradually increased as the stirring rate increased from zero, consistent with the decrease in iodine content and increase in deiodination rate observed in *Sargassum fusiforme* in Table 10. This undoubtedly provides further substantial experimental evidence for the biosorption and deiodination of iodine by *Chlamydomonas reinhardtii*.

[0135] The above experimental results indicate that incubating Sargassum fusiforme in tap water can remove iodine from Sargassum fusiforme. Chlamydomonas reinhardtii concentrates iodine on its surface through biosorption, thus exerting its iodine removal effect. Thorough stirring of the incubation suspension is crucial during the treatment process. This not only promotes the growth of Chlamydomonas reinhardtii but also ensures sufficient contact between the algae and Sargassum fusiforme, maximizing the adsorption and removal of iodine. Therefore, only thorough stirring during the incubation process can achieve optimal iodine removal results.

[0136] In summary, this invention provides a novel application of Chlamydomonas reinhardtii for iodine removal and a typical case study of its application in the deiodization of edible macroalgae. The Chlamydomonas reinhardtii biosorption deiodization technology of this invention can effectively remove iodine from edible macroalgae, reducing their iodine content. Chlamydomonas reinhardtii is a recognized safe food ingredient. Therefore, the technical method of this invention can be used in the food industry, specifically for processing and producing low-iodine seaweed ingredients such as deiodized Sargassum fusiforme, kelp, wakame, and nori. The technical method of this invention allows for direct incubation with tap water when treating seaweed with Chlamydomonas reinhardtii, saving significant costs associated with purifying and preparing pure water, thus possessing practical application value.

[0137] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. Application of Chlamydomonas reinhardtii in seaweed deiodination.

2. The application according to claim 1, characterized in that, The seaweed includes one or more of Sargassum fusiforme, kelp, wakame seaweed, and Porphyra yezoensis.

3. A method for removing iodine from seaweed, characterized in that, The method includes: adding *Chlamydomonas reinhardtii* to a medium of water to obtain a *Chlamydomonas reinhardtii* suspension; adding seaweed to the *Chlamydomonas reinhardtii* suspension at a certain solid-liquid ratio for incubation treatment to complete the deiodination of the seaweed.

4. The method according to claim 3, characterized in that, The concentration of *Chlamydomonas reinhardtii* in the suspension is 0.1-20% (w / v), and the incubation time is 10-200 min. Preferably, the concentration of Chlamydomonas reinhardtii in the suspension is 0.1-10% (w / v), and the incubation time is 20-180 min.

5. The method according to claim 4, characterized in that, The seaweed is Sargassum fusiforme, the concentration of Chlamydomonas reinhardtii in the suspension is 0.1-10% (w / v), and the incubation time is 30-180 min; Preferably, the concentration of *Chlamydomonas reinhardtii* in the suspension is 0.5-10% (w / v), and the incubation time is 60-120 min; or the concentration of *Chlamydomonas reinhardtii* in the suspension is 2% (w / v), and the incubation time is 60 min; or the concentration of *Chlamydomonas reinhardtii* in the suspension is 5-10% (w / v), and the incubation time is 30 min.

6. The method according to claim 4, characterized in that, The seaweed is kelp, the concentration of Chlamydomonas reinhardtii in the suspension is 0.1-2% (w / v), and the incubation time is 60-180 min; Preferably, the concentration of *Chlamydomonas reinhardtii* in the suspension is 0.1-0.5% (w / v), and the incubation time is 60-120 min; or the concentration of *Chlamydomonas reinhardtii* in the suspension is 1-2% (w / v), and the incubation time is 60 min.

7. The method according to claim 4, characterized in that, The seaweed is wakame, the concentration of Chlamydomonas reinhardtii in the suspension is 0.1-5% (w / v), and the incubation time is 60-180 min; Preferably, the concentration of Chlamydomonas reinhardtii in the suspension is 0.5-2% (w / v), and the incubation time is 120-180 min. More preferably, the concentration of Chlamydomonas reinhardtii in the suspension is 1-2% (w / v), and the incubation time is 120-180 min; More preferably, the concentration of Chlamydomonas reinhardtii in the suspension is 2% (w / v), and the incubation time is 120 min.

8. The method according to claim 4, characterized in that, The seaweed is Porphyra yezoensis, the concentration of Chlamydomonas reinhardtii in the suspension is 0.1-2% (w / v), and the incubation time is 60-180 min; Preferably, the concentration of *Chlamydomonas reinhardtii* in the suspension is 0.1-0.5% (w / v), and the incubation time is 120-180 min; more preferably, the concentration of *Chlamydomonas reinhardtii* in the suspension is 0.1-0.5% (w / v), and the incubation time is 180 min. Preferably, the concentration of *Chlamydomonas reinhardtii* in the suspension is 1-2% (w / v), and the incubation time is 60-180 min; more preferably, the concentration of *Chlamydomonas reinhardtii* in the suspension is 1-2% (w / v), and the incubation time is 120-180 min; even more preferably, the concentration of *Chlamydomonas reinhardtii* in the suspension is 1-2% (w / v), and the incubation time is 180 min.

9. The method according to claim 3, characterized in that, The concentration of Chlamydomonas reinhardtii in the suspension is 0.1-20% (w / v), the solid-liquid ratio is 1:2.5-1:100 (g / mL), and the mass ratio of seaweed to Chlamydomonas reinhardtii is 1:0.05-1:

1. Preferably, the concentration of *Chlamydomonas reinhardtii* in the suspension is 0.5-10% (w / v), the solid-liquid ratio is 1:2.5-1:50 (g / mL), and the mass ratio of seaweed to *Chlamydomonas reinhardtii* is 1:0.1-1:0.

5. Preferably, the concentration of Chlamydomonas reinhardtii in the suspension is 10-20% (w / v), the solid-liquid ratio is 1:2.5-1:5 (g / mL), and the mass ratio of seaweed to Chlamydomonas reinhardtii is 1:0.2-1:0.

5.

10. The method according to claim 3, characterized in that, The incubation treatment is either an oscillation incubation treatment or a stirring incubation treatment; The incubation temperature is 15-30℃, preferably 20-25℃, and more preferably 25℃; and / or the oscillation frequency of the oscillation incubation and / or the stirring speed of the stirring incubation are 100-200 rpm, preferably 150-200 rpm, and more preferably 200 rpm.

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