Method for producing culture substrate for algae

Abstract

This invention provides a method for producing a culture substrate for algae that reduces the amount of concrete wastewater discharged and improves the production efficiency of algae by increasing the growth rate of algae. [Solution] The present invention provides a method for producing a culture substrate for algae, characterized by adding nitrogen and phosphorus to concrete wastewater mainly composed of calcium ions and sulfate ions to produce a culture substrate for algae. As the concrete wastewater, wash water used to clean the inside of a concrete mixer after concrete mixing may be used.

Description

[Technical Field]

[0001] This invention relates to a method for producing a culture substrate for algae. [Background technology]

[0002] Traditionally, the amount of concrete waste generated during the manufacturing and demolition of concrete has been a concern, and methods for recycling concrete waste have been considered. Currently, one method of utilizing concrete waste is being researched: using it as a raw material for cultivating algae.

[0003] Patent Document 1 discloses an algae cultivation system that utilizes concrete waste materials. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-144299 [Overview of the project] [Problems that the invention aims to solve]

[0005] According to the algae cultivation system disclosed in Patent Document 1, a sufficient amount of CO2 can be supplied according to the quantity and growth of the algae, and concrete waste can be effectively utilized. However, while coarse particles with a particle size of 1 mm to 5 mm, which are crushed by a raw material crusher, are used, fine particles with a particle size of less than 1 mm are used as raw material for cement clinker, and no method for utilizing the fine particles and wastewater components for algae cultivation is disclosed. In other words, there is a problem in that concrete wastewater cannot be utilized in the cultivation system.

[0006] Therefore, the present invention has been devised in view of the above-described problems, and an object thereof is to provide a method for producing a culture medium for algae, which reduces the amount of waste concrete drainage and improves the production efficiency of algae by improving the growth rate of algae.

Means for Solving the Problems

[0007] The method for producing a culture medium for algae according to the first invention is characterized in that nitrogen and phosphorus are added to concrete drainage mainly composed of calcium ions and sulfate ions to produce a culture medium for algae.

[0008] The method for producing a culture medium for algae according to the second invention is characterized in that, in the first invention, the washing water used for washing inside the concrete mixer after concrete mixing is used as the concrete drainage.

Effects of the Invention

[0009] According to the first invention, nitrogen and phosphorus are added to concrete drainage mainly composed of calcium ions and sulfate ions. Therefore, it is possible to produce a culture medium for improving the growth rate of algae by utilizing the concrete drainage. As a result, the amount of waste concrete drainage can be reduced, and the production efficiency of algae can be improved by improving the growth rate of algae.

[0010] According to the second invention, the washing water used for washing inside the concrete mixer after concrete mixing is used. Therefore, it is possible to produce a culture medium for algae rich in calcium ions and sulfate ions. As a result, the production efficiency of algae can be further improved by further improving the growth rate of algae.

Brief Description of the Drawings

[0011] [Figure 1] Figs. 1(a) to 1(b) are graphs showing the experimental results regarding the cell density of algae comparing the examples and comparative examples according to the present invention. [Figure 2]Figures 2(a) to 2(b) are graphs showing the experimental results regarding the protein content, comparing the examples and comparative examples according to the present invention. [Figure 3] Figures 3(a) to 3(b) are graphs showing the experimental results regarding the carbohydrate content, comparing the examples and comparative examples according to the present invention. [Figure 4] Figures 4(a) to 4(b) are graphs showing the experimental results regarding the lipid content, comparing the examples and comparative examples according to the present invention. [Figure 5] Figures 5(a) to 5(b) are graphs showing the experimental results regarding the chlorophyll a content, comparing the examples and comparative examples according to the present invention. [Figure 6] Figures 6(a) to 6(b) are graphs showing the experimental results regarding the chlorophyll b content, comparing the examples and comparative examples according to the present invention. [Figure 7] Figures 7(a) to 7(b) are graphs showing the experimental results regarding the carotenoid content, comparing the examples and comparative examples according to the present invention.

Mode for Carrying Out the Invention

[0012] Hereinafter, an example of a method for producing a culture substrate for algae as an embodiment of the present invention will be described in detail while referring to the drawings. Note that the configurations in each drawing are schematically described for the purpose of explanation, and for example, the sizes of each configuration and the size ratios between configurations may be different from those in the drawings.

[0013] (Method for Producing a Culture Substrate for Algae) Referring to the drawings, an example of the method for producing a culture substrate for algae in the present embodiment will be described.

[0014] First, the culture substrate for algae will be described.

[0015] <Culture Substrate for Algae> The culture substrate for algae is used, for example, to supply algae and promote their growth. The culture substrate for algae according to the present invention is made from concrete wastewater mainly composed of calcium ions and sulfate ions, and is particularly rich in sulfate ions, which are nutrients necessary for algal growth and are indispensable for the synthesis of amino acids and proteins.

[0016] Furthermore, the culture substrate for algae is supplemented with nitrogen and phosphorus, which are necessary for promoting algal growth, in addition to the concrete wastewater. By using such a culture substrate for algae, it is possible to improve the growth rate of algae while utilizing concrete wastewater. This reduces the amount of concrete wastewater to be discarded and improves the efficiency of algal production by increasing the growth rate of algae.

[0017] The culture substrate for algae contains, for example, calcium ions and sulfate ions. The culture substrate for algae may also contain components such as nitrogen and phosphorus, as well as sodium ions, potassium ions, chloride ions, nitrate ions, etc.

[0018] The following are examples of suitable ion concentrations for the culture substrate for algae. The culture substrate for algae may contain, for example, calcium ions in a concentration of 100 mg / L to 1600 mg / L. High concentrations of calcium ions have the effect of promoting the cell wall structure and growth of algae, but concentrations exceeding 1600 mg / L may cause stress to the algae due to excessive ion concentrations. The culture substrate for algae may also contain, for example, sulfate ions in a concentration of 20 mg / L to 1200 mg / L, and more preferably 250 mg / L to 1200 mg / L. Sulfate ions play an important role in sulfur metabolism and have the effect of promoting the growth of algae, but concentrations below 250 mg / L carry the risk of nutrient deficiency, and concentrations above 1200 mg / L may increase stress on the algae due to pH fluctuations, etc.

[0019] Furthermore, the culture substrate for algae may contain, for example, 150 mg-N / L to 200 mg-N / L of nitrogen. Nitrogen is necessary for protein synthesis in algae, and concentrations above 150 mg-N / L promote growth, but concentrations exceeding 200 mg-N / L may cause stress to the algae due to excessive nutrient supply. In addition, the culture substrate for algae may contain, for example, 40 mg-P / L to 50 mg-P / L of phosphorus. Phosphorus is an important component for energy metabolism and cell division in algae, and concentrations above 40 mg-P / L can stably promote algal growth, but concentrations exceeding 50 mg-P / L may conversely lead to excessive supply and risk stress to the algae.

[0020] Furthermore, the culture substrate for algae may contain, for example, 20 mg / L to 40 mg / L of sodium ions. Sodium contributes to regulating the osmotic pressure of algae, and while a moderate osmotic pressure can be maintained at concentrations of 20 mg / L or higher, concentrations exceeding 40 mg / L may stress the algae. The culture substrate for algae may also contain, for example, 20 mg / L to 60 mg / L of potassium ions. Potassium supports the enzyme activity of algae and promotes growth at concentrations of 20 mg / L or higher, but excessive concentrations exceeding 60 mg / L may be harmful to the algae. The culture substrate for algae may also contain, for example, 8 mg / L to 15 mg / L of chloride ions. Chloride ions are an important component in regulating the osmotic pressure of algae, and it is thought that growth can be promoted without stressing the algae within the range of 8 mg / L to 15 mg / L. The culture substrate for algae may also contain, for example, 3 mg-N / L to 200 mg-N / L of nitrate ions. Nitrate ions are a major nitrogen source for algae, and within the range of 3 mg-N / L to 200 mg-N / L, they can promote algal growth while avoiding excessive nutrient supply.

[0021] By using an algal culture substrate that satisfies the above ion concentrations, the growth of algae can be more reliably promoted.

[0022] The culture substrate for algae is, for example, a liquid. It is used, for example, as a liquid culture medium for algae. The culture substrate for algae has a pH of approximately 10. In addition to liquid culture substrates, the culture substrate for algae may also be a highly storable powdered culture substrate, a pelletized culture substrate, or a gel-like culture substrate or a solid block-like culture substrate that allows for stable nutrient supply.

[0023] Powdered culture substrate is a culture substrate that concentrates nutrients for algae and can be dissolved in water and used as a liquid culture medium. Powdered culture substrate has excellent storage properties, is easy to store, and is convenient because the concentration can be adjusted according to the culture conditions at the time of use. Pellet-type culture substrate is a culture substrate that has been compressed and molded into small pellets and has high sedimentation properties, making it suitable for supplying benthic algae mainly grown in aquariums and culture tanks. Pellet-type culture substrate is convenient because the supply amount is easy to control and diffusion is suppressed more than powder, allowing for localized nutrient supply.

[0024] Gel culture substrates are culture substrates formed by solidifying alginate or agar into a gel-like state. They can supply nutrients to algae gradually, making them suitable when quantitative nutrient supply is required. Gel culture substrates are highly convenient because they release nutrients slowly, allowing for a stable nutrient supply over a certain period. Solid block culture substrates, on the other hand, are culture substrates processed into solid blocks. They utilize the property of slowly dissolving in water and are used in large culture tanks and ponds. Solid block culture substrates are highly convenient because they allow for long-term nutrient supply and reduce the frequency of culture substrate replacement, thus simplifying maintenance.

[0025] Any known algae may be used as the algae to be supplied as culture substrate for algae. Specifically, for example, species of the genera Scenedesmus, Chlorella, Euglenid, Arthrospira, and other freshwater microalgae may be used.

[0026] Next, we will explain the method for producing culture substrates for algae.

[0027] For example, a method for producing culture substrates for algae is to use calcium ions (Ca 2+ ) and sulfate ions (SO4 2- Nitrogen and phosphorus are added to concrete wastewater, which mainly consists of ). In this case, a culture substrate for improving the growth rate of algae can be produced by utilizing concrete wastewater. This reduces the amount of concrete wastewater to be discarded and improves the efficiency of algae production by improving the growth rate of algae.

[0028] Specifically, sodium nitrate (NaNO3) and potassium dihydrogen phosphate (KH2PO4), diluted 200 times, are added to the concrete wastewater. At this time, the solutes are adjusted so that, for example, the nitrogen concentration is approximately 176 mg / L and the phosphorus concentration is approximately 42 mg / L per liter of concrete wastewater. Note that the additives are not limited to these, and any salt or other substance that allows for adjustment of nitrogen and phosphorus concentrations may be used, and any nitrogen and phosphorus compounds that can add nitrogen and phosphorus may be used. In addition, known plant nutrient solutions (liquid fertilizers) containing nitrogen and phosphorus may be used as additives.

[0029] <Concrete drainage> Concrete wastewater is alkaline wastewater generated during the production of ready-mix concrete, etc. For example, concrete wastewater has a pH of approximately 12.

[0030] Concrete wastewater can be used, for example, wastewater containing dissolved concrete components, which is generated by flushing out concrete waste materials remaining in ready-mix concrete manufacturing equipment. Other types of concrete wastewater may be used, such as wastewater generated when flushing out concrete residue after dismantling formwork after concrete placement, wastewater generated when flushing out concrete deposits adhering to the inside of pumps and pipes after concrete placement, slurry wastewater generated when flushing out water for surface cooling and dust suppression during cutting and polishing of concrete surfaces, and wastewater generated when flushing out formwork and products during the manufacturing process of precast concrete products.

[0031] Concrete wastewater can be used, for example, the wash water used to clean the inside of a concrete mixer after concrete mixing. In this case, a culture substrate for algae rich in calcium ions and sulfate ions can be produced. This can further improve the efficiency of algae production by increasing the growth rate of algae. Concrete wastewater, which is mainly liquid, contains many calcium ions, sulfate ions, and fine solid matter (slurry components) that have dissolved when it came into contact with concrete during the washing process, and these components contribute to promoting algae growth. In contrast, concrete waste generated during building demolition, etc., is mainly solid components such as aggregates and cement paste residues, and the ionic components it contains are different from those of concrete wastewater, so it cannot contribute to promoting algae growth.

[0032] For concrete wastewater, in addition to using the wash water as described above, filtered water from which impurities have been removed in a filtration tank, or settled water from which fine impurities have been removed by coagulation and sedimentation treatment in a sedimentation tank may be used. When the wash water is used as is, the concentration of calcium ions and sulfate ions is high, and these components can further promote the growth of algae. When the wash water is filtered and settled, impurities and fine impurities are removed, creating a cleaner environment more suitable for algae growth, and further promoting algae growth by reducing stress on the algae.

[0033] Concrete wastewater has, for example, an EC value (fertilizer concentration) of approximately 5.5 mS / cm to approximately 7.3 mS / cm. Concrete wastewater has, for example, a TDS value (dissolved solids concentration) of approximately 5 ppt. Concrete wastewater has, for example, a Salt value (salinity concentration) of approximately 2.7 ppt to approximately 3.7 ppt.

[0034] According to this embodiment, nitrogen and phosphorus are added to concrete wastewater, which mainly consists of calcium ions and sulfate ions. Therefore, a culture substrate for improving the growth rate of algae can be produced using concrete wastewater. This reduces the amount of concrete wastewater discarded and improves the efficiency of algae production by increasing the growth rate of algae.

[0035] Furthermore, according to this embodiment, the washing water used to clean the inside of the concrete mixer after concrete mixing is used. Therefore, it is possible to produce a culture substrate for algae that is rich in calcium ions and sulfate ions. This makes it possible to further improve the production efficiency of algae by further improving the growth rate of algae. [Examples]

[0036] The following describes in detail the algal growth-promoting effect of the algal culture substrate according to the present invention, citing examples of the present invention and comparative examples using the embodiments described above. In this experiment, changes in the cell density of algae provided with the algal culture substrate, as well as changes in the content of proteins, carbohydrates, lipids, and pigments, were evaluated. The pigments contained in algae were used as one of the indicators of the growth-promoting effect because they are related to the growth and photosynthetic capacity of algae. In particular, among the pigments, the content of chlorophyll a, the main pigment that converts light energy into chemical energy through algal photosynthesis, chlorophyll b, which broadens the range of light that can be used for photosynthesis, and carotenoids, which help to counteract nutrient deficiencies and environmental stresses, were evaluated.

[0037] The production conditions for the culture substrate for algae were as follows:

[0038] To verify the algal growth promoting effect of culture substrates for algae, particularly when comparing the use of concrete wastewater, we prepared two examples of the present invention: Examples 1 and 2, which were prepared by adding additives to concrete wastewater, and Comparative Examples 1 and 2, which were prepared by adding additives to distilled water without using concrete wastewater. Example 1 of the present invention is a combination of concrete wastewater and a commercially available plant nutrient solution, while Example 2 of the present invention is a combination of concrete wastewater and nitrogen and phosphorus compounds. Comparative Example 1 is a combination of distilled water and a commercially available plant nutrient solution, while Comparative Example 2 is a combination of distilled water and nitrogen and phosphorus compounds.

[0039] For concrete wastewater, treated sedimentation water was used. Specifically, the wash water discharged when flushing the inside of a concrete mixer used for ready-mix concrete production was filtered in a filtration tank to produce filtered water, and then treated sedimentation water was produced by coagulation and sedimentation treatment of this filtered water in a sedimentation tank. The ionic component concentrations of the wash water, filtered water, and treated sedimentation water are shown in Table 1, and other characteristics are shown in Table 2.

[0040] [Table 1]

[0041] [Table 2]

[0042] For the algal culture substrate of Example 1 of the present invention, 5 mg of the hydroponic liquid fertilizer "Ouchi no Yasai One-Resolution C" was added to 1 L of concrete wastewater. In addition, the pH was lowered from 12.1 before addition to 10, and the concentration of the liquid after addition was adjusted to approximately 176.37 mg / L for nitrogen and approximately 42.16 mg / L for phosphorus.

[0043] For the algal culture substrate of Example 2 of the present invention, 5 mL of a 35 g-N / L sodium nitrate solution and 5 mL of 8.4 g-P / L potassium dihydrogen phosphate were added to 1 L of concrete wastewater. In addition, the pH was lowered from 12.1 before addition to 10, and the concentration of the liquid after addition was adjusted to approximately 176.37 mg / L for nitrogen and approximately 42.16 mg / L for phosphorus.

[0044] For the culture substrate for algae in Comparative Example 1, 5 mg of the hydroponic liquid fertilizer "Ouchi no Yasai One-Resolution C" was added to 1 L of distilled water. The pH was adjusted to 6.7, and the concentration of the liquid after addition was adjusted to approximately 176.37 mg / L for nitrogen and approximately 42.16 mg / L for phosphorus.

[0045] For the algal culture substrate in Comparative Example 2, 5 mL of a 35 g-N / L sodium nitrate solution and 5 mL of an 8.4 g-P / L potassium dihydrogen phosphate were added to 1 L of distilled water. The pH was adjusted to 6.7, and the concentration of the liquid after addition was adjusted to approximately 176.37 mg / L for nitrogen and approximately 42.16 mg / L for phosphorus.

[0046] The algae used as the culture substrate for algae was Scenedesmus sp. at a dry weight of 400 mg / L.

[0047] The algal culture conditions were as follows: the algae were supplied to a beaker containing liquid algal culture substrate for 7 days. A Sanyo Electric Co., Ltd. "MIR-153" incubator with light was used to adjust the illuminance inside the beaker to 8000 lux. A "LabServ Digital Orbital Shaker FS120460LJ" was used to continuously apply 140 rpm of vibration to the beaker. The culture was carried out at room temperature of 25°C.

[0048] To evaluate changes in algal cell density, algae cultured for 7 days in an algal culture substrate were evaluated using cell density and MLVSS (Mixed Liquor Volatile Suspended Solids) values ​​as indicators. Cell density is an indicator that shows how much individual algal cells are proliferating in the culture medium, and since it measures the number of cells themselves, it is suitable for understanding the rate and amount of growth. The MLVSS value is an indicator that represents the biomass of microorganisms and algae, and it shows the total mass of organic components (biomass) in the culture medium. Since it reflects the size of each cell and the amount of organic matter contained, it is suitable for understanding the increase in biomass and the concentration of organic matter in the entire culture. There is generally a positive correlation between cell density and MLVSS value. Therefore, by evaluating both cell density and MLVSS value in combination, the efficiency of algal growth and changes in biomass can be analyzed in detail. Cell density was evaluated using microscopy. For details, take a certain amount of sample from the culture medium and use a Sunlead glass bacterial counting chamber "A161" under the microscope of an AS ONE Corporation biological microscope "LRM18B / T" to count 1 m 2The number of cells per unit volume was measured by counting and standardizing that number. Alternatively, the number may be measured using a counting chamber manufactured by Hausmann, or by using instruments such as flow cytometry or automated cell counters. For counting using an automated cell counter, the number of cells may be measured using a standardized setting, such as the Z2 automated cell counter manufactured by Beckman Coulter. Subsequently, the number of cells per unit volume (cell density) was calculated based on the measured number of cells. The calculated number of cells is usually expressed as the number of cells per unit volume [mL]. The MLVSS value was evaluated using the measurement method based on APHA's "Standard Methods for the Examination of Water and Wastewater". Specifically, a certain amount of sample was taken from the culture medium, and the solid matter was filtered using filter paper or a glass fiber filter "GF / C" manufactured by Whatman® as a filter. The solid matter remaining on the filter was then dried at 105°C for 1 hour to remove moisture. The dried sample was then strongly heated at 550°C for 20-30 minutes, causing the organic matter to volatilize and leaving only the inorganic matter. Subsequently, the MLVSS value was calculated based on the mass difference before and after ignition. The calculated MLVSS value is usually expressed as the amount of organic components per unit volume (mg / L).

[0049] To evaluate the changes in the protein content of algae, the Lowry method was used to evaluate algae cultured for 7 days in an algal culture substrate (Reference: A rapid and general method for measurement of protein in micro-algal biomass - ScienceDirect).

[0050] To evaluate the changes in the carbohydrate content of algae, the phenol-sulfuric acid method was used to evaluate algae cultured for 7 days in an algal culture substrate (Reference: An improved henol-sulfuric acid method for the quantitative measurement of total carbohydrates in algal biomass - ScienceDirect).

[0051] To evaluate the changes in the lipid content of algae, the Bligh-Dyer method was used to evaluate algae cultured for 7 days in an algal culture substrate (Reference: Liquid Extraction: Bligh and Dyer | SpringerLink).

[0052] To evaluate the changes in the pigment content of algae, chlorophyll a, chlorophyll b, and carotenoids were extracted with methanol from algae cultured for 7 days in an algal culture substrate and analyzed using a spectrophotometer (Reference:

[34] Chlorophylls and carotenoids: Pigments of photosynthetic biomembranes - ScienceDirect).

[0053] <Evaluation of algal cell density> Figure 1(a) and Table 3 show the results of comparing Example 1 of the present invention and Comparative Example 1, both of which were treated with plant nutrient solution, regarding the evaluation of algal cell density. The pH after 7 days was 8.8 for Example 1 and 8.3 for Comparative Example 1. The numbers in parentheses in Table 3 for the initial (day 0) and 7-day entries represent the MLVSS values.

[0054] [Table 3]

[0055] According to Figure 1(a) and Table 3, the cell density of algae cultured for 7 days in the culture substrate of Example 1 of the present invention was 1.79 [10 6cells / mL], the cell density after 1 day was 2.00[10 6 cells / mL], the cell density after 2 days was 2.38[10 6 cells / mL], the cell density after 3 days was 2.80[10 6 cells / mL], the cell density after 4 days was 3.18[10 6 cells / mL], the cell density after 5 days was 3.57[10 6 cells / mL], the cell density after 6 days was 3.73[10 6 cells / mL], the cell density after 7 days was 3.84[10 6 cells / mL]. Also, the MLVSS value was such that the initial MLVSS value was 400[mg / L] and the MLVSS value after 7 days was 858[mg / L].

[0056] Also, the cell density of the algae cultured for 7 days in the culture medium of Comparative Example 1 was such that the initial cell density was 1.79[10 6 cells / mL], the cell density after 1 day was 1.95[10 6 cells / mL], the cell density after 2 days was 2.26[10 6 cells / mL], the cell density after 3 days was 2.57[10 6 cells / mL], the cell density after 4 days was 3.01[10 6 cells / mL], the cell density after 5 days was 3.28[10 6 cells / mL], the cell density after 6 days was 3.40[10 6 cells / mL], the cell density after 7 days was 3.51[10 6 cells / mL]. Also, the MLVSS value was such that the initial MLVSS value was 400[mg / L] and the MLVSS value after 7 days was 784[mg / L].

[0057] Based on the above results, it was found that the cell density of algae cultured for 7 days in the culture substrate of Example 1 of the present invention was improved compared to Comparative Example 1. Furthermore, the MLVSS value of algae cultured for 7 days in the culture substrate of Example 1 of the present invention was improved compared to Comparative Example 1, indicating a greater increase in the biomass of the algae. This is thought to be due to the nutrients abundantly contained in the concrete wastewater, which is the raw material for Example 1 of the present invention, contributing to the growth of the algae, and demonstrating that the presence or absence of nutrients has a significant impact on the growth of algae. Therefore, it can be said that the growth rate of algae can be improved by using an algal culture substrate to which plant nutrients have been added to concrete wastewater. In addition, it is expected that algae cultured using the algal culture substrate of the present invention can be utilized as feed or as a raw material for culture substrates. This can improve the convenience of producing feed or culture substrates.

[0058] Furthermore, regarding the evaluation of algal cell density, the results of comparing Example 2 of the present invention, in which nitrogen and phosphorus compounds were added, with Comparative Example 2 are shown in Figure 1(b) and Table 4. The pH after 7 days was 8.8 for Example 2 of the present invention and 8.3 for Comparative Example 2. In Table 4, the numbers in parentheses for the initial (day 0) and 7-day entries represent the MLVSS values.

[0059] [Table 4]

[0060] According to Figure 1(b) and Table 4, the cell density of algae cultured for 7 days in the culture substrate of Example 2 of the present invention was 1.79 initially [10 6 cells / mL], 2.00 after 1 day [10 6 cells / mL], 2 days later was 2.03[10 6 [cells / mL], 2.32 after 3 days [10 6 cells / mL], 2.65 after 4 days [10 6 [cells / mL], 3.03 after 5 days [10 6 [cells / mL], 3.26 after 6 days [10 6 [cells / mL], 3.50 after 7 days [10 6The value was [cells / mL]. Furthermore, the MLVSS value was 400 [mg / L] initially, and 782 [mg / L] after 7 days.

[0061] Furthermore, the cell density of algae cultured in the culture substrate of Comparative Example 2 for 7 days was 1.79 initially [10 6 [cells / mL], 1.92 after 1 day [10 6 cells / mL], 1.98 after 2 days [10 6 [cells / mL], 2.12 after 3 days [10 6 cells / mL], 2.26 after 4 days [10 6 [cells / mL], 2.32 after 5 days [10 6 [cells / mL], 2.36 after 6 days [10 6 cells / mL], 2.43 after 7 days [10 6 The value was [cells / mL]. Furthermore, the MLVSS value was 400 [mg / L] initially, and 543 [mg / L] after 7 days.

[0062] Based on the above results, it was found that even when nitrogen compounds and phosphorus compounds were added instead of plant nutrient solution, the cell density of algae cultured for 7 days in the culture substrate of Example 2 of the present invention was improved compared to Comparative Example 2. Furthermore, the MLVSS value of algae cultured for 7 days in the culture substrate of Example 2 of the present invention was improved compared to Comparative Example 2, indicating a greater increase in algal biomass. Therefore, it can be said that using an algal culture substrate to which nitrogen compounds and phosphorus compounds have been added to concrete wastewater can improve the growth rate of algae.

[0063] <Evaluation of the protein content of algae> The evaluation of the protein content of algae is shown in Figure 2(a) and Table 5, comparing Example 1 of the present invention, in which a plant nutrient solution was added, with Comparative Example 1. Note that "mg / g DW" refers to the content per gram of algae based on dry weight, and the same applies hereafter.

[0064] [Table 5]

[0065] According to Figure 2(a) and Table 5, the protein content of algae cultured for 7 days in the culture substrate of Example 1 of the present invention was 301.30 [mg / g DW] initially, 325.30 [mg / g DW] after 3 days, and 323.25 [mg / g DW] after 7 days.

[0066] Furthermore, the protein content of algae cultured in the culture substrate of Comparative Example 1 for 7 days was 301.30 [mg / g DW] initially, 315.00 [mg / g DW] after 3 days, and 309.65 [mg / g DW] after 7 days.

[0067] Based on the above results, it was found that the protein content of algae cultured for 7 days in the culture substrate of Example 1 of the present invention was improved compared to Comparative Example 1. This is thought to be because ionic components such as calcium and potassium contained in the concrete wastewater, which is the raw material for Example 1 of the present invention, promote protein synthesis in the algae. Therefore, it can be said that by using the algal culture substrate of Example 1 of the present invention, which is obtained by adding plant nutrient solution to concrete wastewater, it is possible to improve the protein content of algae. Furthermore, it is expected that algae cultured using the algal culture substrate of the present invention can be used as a raw material for high-protein feed or high-protein culture substrate. This will improve the convenience of producing high-protein feed or high-protein culture substrate.

[0068] On the other hand, in Comparative Example 1, the distilled water does not contain nutrients, and the nutrients contained in the additives are insufficient, which is thought to have suppressed the increase in the protein content of the algae. For this reason, it is not possible to improve the protein content of the algae with the culture substrate of Comparative Example 1.

[0069] Furthermore, regarding the evaluation of the protein content of algae, the results of comparing Example 2 of the present invention, in which nitrogen compounds and phosphorus compounds were added, with Comparative Example 2 are shown in Figure 2(b) and Table 6.

[0070] [Table 6]

[0071] According to Figure 2(b) and Table 6, the protein content of algae cultured for 7 days in the culture substrate of Example 2 of the present invention was 301.30 [mg / g DW] initially, 321.85 [mg / g DW] after 3 days, and 319.30 [mg / g DW] after 7 days.

[0072] Furthermore, the protein content of algae cultured in the culture substrate of Comparative Example 2 for 7 days was 301.30 [mg / g DW] initially, 303.15 [mg / g DW] after 3 days, and 303.65 [mg / g DW] after 7 days.

[0073] Based on these results, it was found that even when nitrogen compounds and phosphorus compounds were added instead of plant nutrient solution, the protein content of algae cultured for 7 days in the culture substrate of Example 2 of the present invention was improved compared to Comparative Example 2. Therefore, it can be said that by using the algal culture substrate of Example 2 of the present invention, in which nitrogen compounds and phosphorus compounds are added to concrete wastewater, it is possible to improve the protein content of algae.

[0074] Furthermore, it was found that the algal culture substrate of Example 2 of the present invention, despite having only nitrogen and phosphorus added, contains almost the same amount of protein as the algal culture substrate of Example 1 of the present invention, which had plant nutrient solution added. This is thought to be because components such as calcium and potassium contained in concrete wastewater promote protein production.

[0075] On the other hand, in Comparative Example 2, the distilled water does not contain nutrients, and the nutrients contained in the additives are insufficient, which is thought to suppress the increase in the protein content of the algae. Therefore, it is not possible to improve the protein content of the algae with the culture substrate of Comparative Example 2.

[0076] <Evaluation of the carbohydrate content of algae> The evaluation of the carbohydrate content of algae is shown in Figure 3(a) and Table 7, comparing Example 1 of the present invention, in which a plant nutrient solution was added, with Comparative Example 1.

[0077] [Table 7]

[0078] According to Figure 3(a) and Table 7, the carbohydrate content of algae cultured for 7 days in the culture substrate of Example 1 of the present invention was 402.80 [mg / g DW] initially, 431.35 [mg / g DW] after 3 days, and 431.70 [mg / g DW] after 7 days.

[0079] Furthermore, the carbohydrate content of algae cultured in the culture substrate of Comparative Example 1 for 7 days was 402.80 [mg / g DW] initially, 415.10 [mg / g DW] after 3 days, and 415.90 [mg / g DW] after 7 days.

[0080] Based on the above results, it was found that the carbohydrate content of algae cultured for 7 days in the culture substrate of Example 1 of the present invention was improved compared to Comparative Example 1. This suggests that the nutrients contained in the concrete wastewater, which is the raw material for Example 1 of the present invention, have a positive effect on the growth of the algae. Therefore, it can be said that by using the algae culture substrate of Example 1 of the present invention, which has plant nutrient solution added to concrete wastewater, it is possible to improve the carbohydrate content of the algae. Furthermore, it is expected that algae cultured using the algae culture substrate of the present invention can be used as a raw material for high-nutrient feed or high-nutrient culture substrate. This will improve the convenience of producing high-nutrient feed or high-nutrient culture substrate.

[0081] On the other hand, in Comparative Example 1, the distilled water does not contain nutrients, and the nutrients contained in the additives are insufficient, which is thought to suppress the increase in the carbohydrate content of the algae. Therefore, it is not possible to improve the carbohydrate content of the algae with the culture substrate of Comparative Example 1.

[0082] Furthermore, regarding the evaluation of the carbohydrate content of algae, the results of comparing Example 2 of the present invention, in which nitrogen compounds and phosphorus compounds were added, with Comparative Example 2 are shown in Figure 3(b) and Table 8.

[0083] [Table 8]

[0084] According to Figure 3(b) and Table 8, the carbohydrate content of algae cultured for 7 days in the culture substrate of Example 2 of the present invention was 402.80 [mg / g DW] initially, 424.35 [mg / g DW] after 3 days, and 418.65 [mg / g DW] after 7 days.

[0085] Furthermore, the carbohydrate content of algae cultured in the culture substrate of Comparative Example 2 for 7 days was 402.80 [mg / g DW] initially, 400.90 [mg / g DW] after 3 days, and 401.70 [mg / g DW] after 7 days.

[0086] Based on these results, it was found that even when nitrogen compounds and phosphorus compounds were added instead of plant nutrient solution, the carbohydrate content of algae cultured for 7 days in the culture substrate of Example 2 of the present invention was improved compared to Comparative Example 2. Therefore, it can be said that by using the algal culture substrate of Example 2 of the present invention, in which nitrogen compounds and phosphorus compounds are added to concrete wastewater, it is possible to improve the carbohydrate content of algae.

[0087] Furthermore, it was found that the algal culture substrate of Example 2 of the present invention, despite having only nitrogen and phosphorus added, contains almost the same amount of carbohydrates as the algal culture substrate of Example 1 of the present invention, which had plant nutrient solution added. This is thought to be because the calcium and sulfates contained in the concrete wastewater promote the production of carbohydrates.

[0088] On the other hand, in Comparative Example 2, the distilled water contains no nutrients, and the nutrients contained in the additives are insufficient, which is thought to suppress the increase in the carbohydrate content of the algae. Therefore, it is not possible to improve the carbohydrate content of the algae with the culture substrate of Comparative Example 2.

[0089] <Evaluation of the lipid content of algae> The evaluation of the lipid content of algae is shown in Figure 4(a) and Table 9, comparing Example 1 of the present invention, in which a plant nutrient solution was added, with Comparative Example 1.

[0090] [Table 9]

[0091] According to Figure 4(a) and Table 9, the lipid content of algae cultured for 7 days in the culture substrate of Example 1 of the present invention was 204.30 [mg / g DW] initially, 157.65 [mg / g DW] after 3 days, and 163.65 [mg / g DW] after 7 days.

[0092] Furthermore, the lipid content of algae cultured in the culture substrate of Comparative Example 1 for 7 days was 204.30 [mg / g DW] initially, 157.15 [mg / g DW] after 3 days, and 158.75 [mg / g DW] after 7 days.

[0093] Based on the above results, it was found that the lipid content of algae cultured for 7 days in the culture substrate of Example 1 of the present invention was reduced to the same level as in Comparative Example 1 and remained stable even after the 3rd day. This is thought to be because the components in the concrete wastewater promote lipid synthesis while simultaneously accelerating its decomposition, resulting in a stable lipid content after decomposition. Therefore, it can be said that by using the algal culture substrate of Example 1 of the present invention, which has plant nutrient solution added to concrete wastewater, it is possible to suppress the increase in the lipid content of algae. Furthermore, algae cultured using the algal culture substrate of the present invention can be expected to be useful as a raw material for low-lipid feed or low-lipid culture substrate. This will improve the convenience of producing low-lipid feed or low-lipid culture substrate.

[0094] Furthermore, regarding the evaluation of the lipid content of algae, the results of comparing Example 2 of the present invention, in which nitrogen compounds and phosphorus compounds were added, with Comparative Example 2 are shown in Figure 4(b) and Table 10.

[0095] On the other hand, in Comparative Example 1, the distilled water did not contain nutrients, and the nutrients contained in the additives were insufficient, so it is thought that lipid synthesis did not proceed and therefore the lipid content did not increase. For this reason, the culture substrate in Comparative Example 1 cannot suppress the increase in the lipid content of algae.

[0096] [Table 10]

[0097] According to Figure 4(b) and Table 10, the lipid content of algae cultured for 7 days in the culture substrate of Example 2 of the present invention was 204.30 [mg / g DW] initially, 165.05 [mg / g DW] after 3 days, and 171.70 [mg / g DW] after 7 days.

[0098] Furthermore, the lipid content of algae cultured in the culture substrate of Comparative Example 2 for 7 days was 204.30 [mg / g DW] initially, 206.95 [mg / g DW] after 3 days, and 205.30 [mg / g DW] after 7 days.

[0099] Based on the above results, it was found that the lipid content of algae cultured for 7 days in the culture substrate of Example 2 of the present invention, to which nitrogen compounds and phosphorus compounds were added instead of plant nutrient solution, was reduced compared to Comparative Example 2. Therefore, it can be said that by using the culture substrate for algae of Example 2 of the present invention, to which nitrogen compounds and phosphorus compounds are added to concrete wastewater, it is possible to suppress the increase in the lipid content of algae.

[0100] Furthermore, it was found that the algal culture substrate of Example 2 of the present invention, despite having only nitrogen and phosphorus added, contained almost the same amount of lipids as the algal culture substrate of Example 1 of the present invention, which had plant nutrient solution added. This is thought to be because the calcium ions and high pH contained in the concrete wastewater created an environment in which lipids were easily broken down, resulting in accelerated lipid decomposition.

[0101] On the other hand, in Comparative Example 2, the lipid content did not decrease but rather tended to increase. This suggests that lipid decomposition did not proceed very well in distilled water. Therefore, the culture substrate in Comparative Example 2 could not suppress the increase in lipid content.

[0102] <Evaluation of pigment content in algae> The evaluation of the chlorophyll a content of algae is shown in Figure 5(a) and Table 11, comparing Example 1 of the present invention, in which a plant nutrient solution was added, with Comparative Example 1.

[0103] [Table 11]

[0104] According to Figure 5(a) and Table 11, the chlorophyll a content of algae cultured for 7 days in the culture substrate of Example 1 of the present invention was 6.44 [μg / mg] initially, 15.79 [μg / mg] after 3 days, and 15.83 [μg / mg] after 7 days.

[0105] Furthermore, the chlorophyll a content of algae cultured for 7 days in the culture substrate of Comparative Example 1 was 6.44 [μg / mg] initially, 11.85 [μg / mg] after 3 days, and 12.92 [μg / mg] after 7 days.

[0106] Based on the above results, it was found that the chlorophyll a content of algae cultured for 7 days in the culture substrate of Example 1 of the present invention was improved compared to Comparative Example 1. This is thought to be because the ionic components such as calcium, potassium, and sulfate contained in the concrete wastewater, which is the raw material for Example 1 of the present invention, promote the photosynthetic ability of the algae and promote the production of pigments. Therefore, it can be said that by using the algal culture substrate of Example 1 of the present invention, which is concrete wastewater to which plant nutrients have been added, it is possible to improve the chlorophyll a content of algae and, consequently, improve the growth rate of algae.

[0107] On the other hand, in Comparative Example 1, the distilled water does not contain nutrients, and the nutrients contained in the additives are insufficient, which is thought to have suppressed the synthesis of chlorophyll a in the algae. For this reason, the culture substrate in Comparative Example 1 cannot improve the chlorophyll a content of the algae or the growth rate of the algae.

[0108] Furthermore, the results of comparing Example 2 of the present invention, in which nitrogen compounds and phosphorus compounds were added, with Comparative Example 2 are shown in Figure 5(b) and Table 12.

[0109] [Table 12]

[0110] According to Figure 5(b) and Table 12, the chlorophyll a content of algae cultured for 7 days in the culture substrate of Example 2 of the present invention was 6.44 [μg / mg] initially, 13.78 [μg / mg] after 3 days, and 12.79 [μg / mg] after 7 days.

[0111] Furthermore, the chlorophyll a content of algae cultured for 7 days in the culture substrate of Comparative Example 2 was 6.44 [μg / mg] initially, 6.66 [μg / mg] after 3 days, and 5.07 [μg / mg] after 7 days.

[0112] Based on these results, it was found that even when nitrogen compounds and phosphorus compounds were added instead of plant nutrient solution, the chlorophyll a content of algae cultured for 7 days in the culture substrate of Example 2 of the present invention was improved compared to Comparative Example 2. Therefore, it can be said that by using the algal culture substrate of Example 2 of the present invention, which has nitrogen compounds and phosphorus compounds added to concrete wastewater, it is possible to improve the chlorophyll a content of algae.

[0113] Furthermore, it was found that the algal culture substrate of Example 2 of the present invention, despite having only nitrogen and phosphorus added, contains almost the same amount of chlorophyll a as the algal culture substrate of Example 1 of the present invention, which has plant nutrient solution added.

[0114] On the other hand, in Comparative Example 2, the distilled water does not contain nutrients, and the nutrients contained in the additives are insufficient, which is thought to suppress the synthesis of chlorophyll a in the algae. For this reason, the culture substrate in Comparative Example 2 cannot improve the chlorophyll a content of the algae or the growth rate of the algae.

[0115] Next, regarding the evaluation of the chlorophyll b content of algae, the results of comparing Example 1 of the present invention, in which a plant nutrient solution was added, with Comparative Example 1 are shown in Figure 6(a) and Table 13.

[0116] [Table 13]

[0117] According to Figure 6(a) and Table 13, the chlorophyll b content of algae cultured for 7 days in the culture substrate of Example 1 of the present invention was 1.35 [μg / mg] initially, 4.16 [μg / mg] after 3 days, and 3.17 [μg / mg] after 7 days.

[0118] Furthermore, the chlorophyll b content of algae cultured in the culture substrate of Comparative Example 1 for 7 days was 1.35 [μg / mg] initially, 3.35 [μg / mg] after 3 days, and 3.86 [μg / mg] after 7 days.

[0119] Based on the above results, it was found that the chlorophyll b content of algae cultured in the culture substrate of Example 1 for 7 days was significantly higher than that of Comparative Example 1 after 3 days. Therefore, it can be said that by using the algal culture substrate of Example 1, which is concrete wastewater to which plant nutrients are added, it is possible to improve the chlorophyll b content of algae and, consequently, the growth rate of algae. However, after 7 days, the chlorophyll b content of algae in the culture substrate of Example 1 decreased. Nevertheless, the peak value of chlorophyll b content in Example 1 was higher than the peak value in Comparative Example 1. This is thought to be because the algae reached their growth peak after 3 days, and then chlorophyll b was decomposed due to changes in nutrient consumption and photosynthesis. In other words, the algal culture substrate of Example 1 can improve the chlorophyll b content of algae at least in the short term. Furthermore, depending on conditions such as nutrient supply and culture period, it may be possible to improve the chlorophyll b content of algae over the long term.

[0120] Furthermore, the results of comparing Example 2 of the present invention, in which nitrogen compounds and phosphorus compounds were added, with Comparative Example 2 are shown in Figure 6(b) and Table 14.

[0121] [Table 14]

[0122] According to Figure 6(b) and Table 14, the chlorophyll b content of algae cultured for 7 days in the culture substrate of Example 2 of the present invention was 1.35 [μg / mg] initially, 3.34 [μg / mg] after 3 days, and 2.66 [μg / mg] after 7 days.

[0123] Furthermore, the chlorophyll b content of algae cultured in the culture substrate of Comparative Example 2 for 7 days was 1.35 [μg / mg] initially, 1.66 [μg / mg] after 3 days, and 0.89 [μg / mg] after 7 days.

[0124] Based on the above results, it was found that the chlorophyll b content of algae cultured for 7 days in the culture substrate of Example 2 of the present invention, to which nitrogen compounds and phosphorus compounds were added instead of plant nutrient solution, was improved compared to Comparative Example 2. Therefore, it can be said that by using the culture substrate for algae of Example 2 of the present invention, to which nitrogen compounds and phosphorus compounds were added to concrete wastewater, it is possible to improve the chlorophyll b content of algae. In addition, similar to Example 1 of the present invention, the chlorophyll b content in Example 2 decreased after 7 days compared to after 3 days. However, the peak value of the chlorophyll b content was higher than the peak value in Comparative Example 2, similar to Example 1 of the present invention.

[0125] Furthermore, it was found that the algal culture substrate of Example 2 of the present invention, despite having only nitrogen and phosphorus added, contains almost the same amount of chlorophyll b as the algal culture substrate of Example 1 of the present invention, which had plant nutrient solution added.

[0126] On the other hand, in Comparative Example 2, the distilled water does not contain nutrients, and the nutrients contained in the additives are insufficient, which is thought to suppress the synthesis of chlorophyll b in the algae. For this reason, the culture substrate in Comparative Example 2 cannot improve the chlorophyll b content of the algae or the growth rate of the algae.

[0127] Next, regarding the evaluation of the carotenoid content of algae, the results of comparing Example 1 of the present invention, in which a plant nutrient solution was added, with Comparative Example 1 are shown in Figure 7(a) and Table 15.

[0128] [Table 15]

[0129] According to Figure 7(a) and Table 15, the carotenoid content of algae cultured for 7 days in the culture substrate of Example 1 of the present invention was 1.00 [μg / mg] initially, 1.54 [μg / mg] after 3 days, and 1.72 [μg / mg] after 7 days.

[0130] Furthermore, the carotenoid content of algae cultured in the culture substrate of Comparative Example 1 for 7 days was 1.00 [μg / mg] initially, 0.85 [μg / mg] after 3 days, and 1.55 [μg / mg] after 7 days.

[0131] Based on the above results, it was found that the carotenoid content of algae cultured for 7 days in the culture substrate of Example 1 of the present invention was slightly higher than that of Comparative Example 1, but was almost the same. This suggests that the algae did not suffer any particular nutrient deficiency or environmental stress from the concrete wastewater used as the raw material for Example 1 of the present invention. In other words, it is clear that the culture substrate for algae of Example 1 of the present invention does not cause excessive stress in the algal culture environment. Therefore, by using the culture substrate for algae of Example 1 of the present invention, which is made by adding plant nutrient solution to concrete wastewater, it is possible to suppress the increase in the carotenoid content of algae and, consequently, improve the growth rate of algae.

[0132] Furthermore, the results of comparing Example 2 of the present invention, in which nitrogen compounds and phosphorus compounds were added, with Comparative Example 2 are shown in Figure 7(b) and Table 16.

[0133] [Table 16]

[0134] According to Figure 7(b) and Table 16, the carotenoid content of algae cultured for 7 days in the culture substrate of Example 2 of the present invention was 1.00 [μg / mg] initially, 1.22 [μg / mg] after 3 days, and 1.94 [μg / mg] after 7 days.

[0135] Furthermore, the carotenoid content of algae cultured in the culture substrate of Comparative Example 2 for 7 days was 1.00 [μg / mg] initially, 4.63 [μg / mg] after 3 days, and 5.47 [μg / mg] after 7 days.

[0136] Based on the above results, it was found that the carotenoid content of algae cultured for 7 days in the culture substrate of Example 2 of the present invention, to which nitrogen compounds and phosphorus compounds were added instead of plant nutrient solution, was lower than that of Comparative Example 2. This is thought to be because in Comparative Example 2, the algae could not grow sufficiently due to a deficiency of nutrients other than nitrogen and phosphorus, resulting in increased stress from light and the environment, and thus promoting the production of carotenoids to increase stress tolerance. On the other hand, it was found that the carotenoid content of Example 2 of the present invention was slightly higher than that of Example 1 of the present invention and Comparative Example 1, but was almost the same. This is thought to be because the concrete wastewater used as the raw material for Example 2 of the present invention supplements the nutrients necessary for algae growth, and the algae do not suffer any particular nutrient deficiency or environmental stress. In other words, it is clear that the culture substrate for algae of Example 2 of the present invention does not cause excessive stress in the algae culture environment. For this reason, it can be said that by using the culture substrate for algae of Example 2 of the present invention, to which nitrogen compounds and phosphorus compounds are added to concrete wastewater, it is possible to suppress the increase in the carotenoid content of algae and, consequently, improve the growth rate of algae.

[0137] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents.

Claims

1. To produce a culture substrate for algae by adding nitrogen and phosphorus to concrete wastewater, which mainly consists of calcium ions and sulfate ions. A method for producing a culture substrate for algae, characterized by the following.

2. As the concrete wastewater, the wash water used to clean the inside of the concrete mixer after concrete mixing is used. A method for producing a culture substrate for algae according to claim 1, characterized by the above.

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