Biological environment-friendly wastewater protein and its long-lasting preservation extraction method

Abstract

The present application relates to the technical field of resource recycling, and particularly relates to a kind of biological environment-friendly wastewater protein and its persistent fresh-keeping extraction method.The method is aimed at the problems of high protein content in fish processing wastewater, difficult separation and easy spoilage of recovered products, and proposes a comprehensive process integrating physical strengthening, composite flocculation and biological stabilization, which realizes efficient enrichment and separation of proteins in wastewater without relying on strong chemical conditions.The obtained protein powder has good solubility, structural stability and storage preservation.The process is simple to operate, low in energy consumption and environmentally friendly, and can realize the resource utilization of fish processing wastewater, providing a new technical approach for biological protein extraction and environmental protection treatment.

Description

Technical Field

[0001] This invention relates to the field of resource recycling technology, specifically to a biological and environmentally friendly wastewater protein extraction method and its long-lasting preservation method. Background Technology

[0002] With the rapid development of the aquatic product processing industry, a large amount of fish generates high-concentration wastewater rich in organic matter during processing such as cutting, trimming, and cleaning. This type of wastewater contains abundant soluble protein and a small amount of fat, representing a potentially high-value resource. However, traditional processes mainly focus on pollution control, emphasizing biochemical degradation or physicochemical removal technologies, without fully considering the regeneration and utilization of usable components. This leads to the direct oxidation and discharge of organic matter, wasting protein resources and increasing the energy consumption and operating costs of the treatment system.

[0003] Currently, wastewater protein is often recovered through chemical flocculation, acid precipitation, or membrane separation. However, these methods generally suffer from high energy consumption, numerous polluting byproducts, poor separation selectivity, and high protein denaturation rates. In addition, the resulting protein typically has defects such as insufficient solubility, easy oxidation and browning, and easy spoilage when stored at room temperature, making it difficult to meet the requirements for resource utilization in the feed and food industries.

[0004] In terms of recovery efficiency, existing flocculation systems mostly rely on single inorganic or organic polymer materials, which have limited adsorption capacity for proteins and floc structure stability, often resulting in small suspended particles that are difficult to settle, leading to incomplete separation. During the dispersion stage, without effective interface enhancement methods, protein molecules in wastewater easily form complex flocs with impurities, affecting the purity of subsequent separation. Especially in high-salt, high-fat environments, proteins easily form stable emulsion systems, making it difficult for traditional static flocculation to achieve efficient removal. Even with fine separation equipment such as membrane filtration, they are easily affected by fouling and clogging, resulting in high maintenance costs. Furthermore, the obtained protein products are prone to discoloration, stickiness, and flavor deterioration during storage due to residual microbial growth and oxidation, resulting in a short shelf life. These issues make the resource recovery of wastewater proteins lack stability and economic viability.

[0005] Furthermore, given the increasing demands for green manufacturing and carbon emission reduction, simply relying on increasing the amount of chemical reagents or introducing expensive equipment is no longer sustainable. The long-standing technical challenge in this field is how to achieve efficient enrichment and separation of wastewater proteins while reducing the amount of added chemical reagents and energy consumption, and ensuring the structural integrity and storage stability of the obtained proteins.

[0006] Therefore, there is an urgent need for a comprehensive process system that combines efficient enrichment and separation, structural protection, and biological preservation, which can improve the recovery rate and ensure the solubility and long-term stability of the obtained protein powder, providing a new technical path for the resource utilization of fish processing wastewater. Summary of the Invention

[0007] In view of this, the purpose of this invention is to propose a biological and environmentally friendly wastewater protein extraction method and a long-lasting preservation method to solve the problems of low wastewater protein recovery rate and easy spoilage of extracted protein.

[0008] To achieve the above objectives, this invention provides a biological and environmentally friendly method for the long-term preservation of proteins in wastewater, comprising the following steps:

[0009] S1 Wastewater Pretreatment: The cleaning wastewater from the production workshop is filtered to remove large suspended solids and fine residues, resulting in clarified pretreated wastewater.

[0010] S2 enrichment treatment: At 20-30℃, micro-nano bubble water is introduced into the pretreated wastewater through a micro-nano bubble water generator to form bubble-containing wastewater;

[0011] S3 Flocculation Separation: After the foamy wastewater enters the solid-liquid separation system, a biological flocculant is added for flocculation, and ultrasonic treatment is applied at the same time. After uniform mixing and static separation, solid and liquid phases are obtained.

[0012] S4 microbial agent treatment: The resulting liquid phase flows into the sewage treatment plant; the resulting solid protein is added with compound probiotics and bio-fermented at 25-65℃, and then freeze-dried to obtain light yellow protein powder.

[0013] Preferably, the filtration to remove large particulate matter in step S1 is performed using a stainless steel screen with a pore size of 1-2 mm.

[0014] Preferably, the filtration to remove fine residue in step S1 is performed using a precision filter element with a pore size of 80-150 μm.

[0015] Preferably, the wastewater from the production workshop cleaning process in step S1 is marine or freshwater fish meat and its by-products, such as fish heads, fish bones, fish skin, and fish scraps.

[0016] Preferably, the micro-nano bubble water in step S2 is generated by passing gas through a micro-nano bubble generator.

[0017] Preferably, the gas is one, two, or a mixture of two or more of the following: air, nitrogen, hydrogen, oxygen, ozone, and carbon dioxide.

[0018] Preferably, the bubble size of the micro-nano bubble water in step S2 is 50-500 nm.

[0019] Preferably, the concentration of bubbles in the micro / nano bubble water in step S2 is 0.1-1.5 × 10⁻⁶. 9 per mL.

[0020] Preferably, the flow rate of the micro / nano bubble water introduced in step S2 is 1.0-5.0 L / min / m 3 .

[0021] Preferably, the amount of clarified pretreated wastewater used in step S2 is 100L.

[0022] Preferably, the ultrasonic instrument in step S3 has a frequency of 30-150kHz, an ultrasonic power of 50-1000W, and an ultrasonic time of 10min.

[0023] Preferably, during the ultrasonic treatment in step S3, the process is paused for 20-40 seconds every 1.5-3 minutes.

[0024] Preferably, the bio-flocculator in step S3 is one, two, or a mixture of two or more of chitosan, starch, and polyglutamic acid.

[0025] Preferably, the chitosan has a molecular weight of 310,000-375,000 Da.

[0026] Preferably, the starch is corn starch with a linear content of 28% and a branched content of 72%.

[0027] Preferably, the polyglutamic acid has a molecular weight of 2,500,000 Da.

[0028] Preferably, in step S3, based on a volume of 100L of foamy wastewater, the amounts of chitosan, corn starch, and polyglutamic acid added are 1.5-2.5g, 1.5-2.5g, and 1.5-2.5g, respectively.

[0029] Preferably, the concentration of the compound probiotic group added in step S4 is 5-15 mL / L.

[0030] Furthermore, the compound probiotic group is composed of Bacillus subtilis, lactic acid bacteria, and polyhydroxyalkanoates in a weight ratio of 5-50:5-50:5-20.

[0031] Preferably, the freeze-drying temperature in step S4 is -25~-15℃ and the time is 6-8h.

[0032] Furthermore, the present invention also provides a bio-friendly wastewater protein.

[0033] The beneficial effects of this invention are:

[0034] The process proposed in this invention achieves efficient extraction and long-term preservation of protein from wastewater through multi-dimensional optimization of physical enhancement, chemical flocculation, and biological stabilization treatment steps, as detailed below:

[0035] First, micro- and nanobubbles have a high specific surface area and long residence time, which can effectively adsorb dispersed protein molecules at the gas-liquid interface, promote their aggregation and enrichment, and significantly improve the mass transfer rate and particle uniformity of the separation reaction, thereby improving separation efficiency and protein fidelity without increasing the chemical dosage.

[0036] Secondly, a compound system consisting of chitosan, corn starch, and polyglutamic acid is used in the flocculation stage. Compared with single natural polysaccharide flocculants, this combination utilizes the complementary characteristics of the cationic active sites of chitosan and the branched structure of corn starch, making the formed flocs more dense and stable, which is conducive to the effective capture and sedimentation of low-concentration proteins. In addition, chitosan helps to maintain the integrity of the protein's tertiary structure and reduces conformational damage during thermomechanical processes. Therefore, the resulting protein powder can quickly recover its dispersed state when dissolved, exhibiting good solubility and absorption performance.

[0037] Finally, in the post-processing stage of the product, a microbial system composed of Bacillus subtilis, lactic acid bacteria and polyhydroxy fatty acid esters is introduced. This system can form a stable biological barrier on the surface of protein powder particles, maintain a low-oxygen environment and continuously produce organic acids and antibacterial metabolites, thereby effectively controlling the re-increase of microorganisms during storage, delaying oxidation and flavor deterioration, and significantly improving the product's preservation performance.

[0038] Compared with chemical preservation methods, this invention has the advantages of being biodegradable and highly safe, and is more in line with the green and environmentally friendly requirements of food and feed processing. In summary, this invention achieves the organic unity of protein separation efficiency, structural stability and biosafety through the synergistic effect of multiple functions. It not only reduces the burden of wastewater treatment, but also realizes the resource utilization of by-products, providing a sustainable and high-value-added green treatment route for the aquatic product processing industry. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in this invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below;

[0040] Figure 1 This is a schematic diagram of the process flow of an embodiment of the present invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0042] The sources or properties of the raw materials used in the embodiments and comparative examples of this invention are as follows:

[0043] Chitosan: molecular weight 350,000 Da, Sigma-Aldrich, catalog number 419419; Corn starch: linear content 28%, branched content 72%; Polyglutamic acid: molecular weight 2,500,000 Da; Complex probiotics: Bacillus subtilis, lactic acid bacteria, and polyhydroxyalkanoates in a weight ratio of 10:10:10, with a viable count of 1×10⁻⁶. 8 CFU / mL;

[0044] Production workshop cleaning drainage: Drainage generated during the cleaning of fish meat, skin, bones, scales, head, and internal organs in the processing of saltwater or freshwater fish, with a protein content of 6g / L and a fat content of 2g / L.

[0045] Example 1: A biological and environmentally friendly wastewater protein extraction method and its long-term preservation method, the specific steps of which are as follows:

[0046] (1) Pretreatment of cleaning wastewater in production workshop: The cleaning wastewater in production workshop is introduced into a mechanical filtration device, and a stainless steel screen with a pore size of 1mm is used to remove large particulate suspended matter. Then, it is further removed by a polyester precision filter element with a pore size of 80μm to obtain clarified pretreated wastewater.

[0047] (2) Micro-nano bubble enrichment treatment: 100L of clarified pretreated wastewater was transferred to a stainless steel reaction tank, and micro-nano bubble water was introduced into it using a micro-nano bubble water generator at an air flow rate of 1.0L / min / m 3 The reaction was carried out at 20°C for 10 minutes to form foamy wastewater.

[0048] (3) Flocculation separation: 100L of foamy wastewater was introduced into the solid-liquid separation system through a valve switching, and then added to a 1L dispersion containing 1.5g chitosan, 1.5g corn starch and 1.5g polyglutamic acid. At the same time, ultrasonic treatment at 30kHz and 50W was applied for 10min. During the ultrasonic treatment, the process was paused for 20s every 1.5min and the stirring speed was maintained at 120rpm. After standing for 8min, air was introduced for air flotation separation for 5min to obtain solid and liquid phases.

[0049] (4) Microbial inoculant treatment:

[0050] After air flotation separation, the solid and liquid phases are separated, and the resulting liquid phase flows into the sewage treatment plant; the resulting solid is resuspended in deionized water, and a compound probiotic group (addition amount is 5 mL / L) is added. After standing at 25℃ for 2 hours, it is then freeze-dried in a freeze dryer to obtain light yellow protein powder. The freezing time is -25℃ and the time is 6 hours.

[0051] Example 2: A biological and environmentally friendly wastewater protein extraction method and its long-term preservation method, the specific steps of which are as follows:

[0052] (1) Pretreatment of cleaning wastewater in production workshop: The cleaning wastewater in production workshop is introduced into a mechanical filtration device, and a stainless steel screen with a pore size of 2mm is used to remove large suspended particles. Then, it is further removed by a polyester precision filter element with a pore size of 100μm to obtain clarified pretreated wastewater.

[0053] (2) Micro-nano bubble enrichment treatment: 100L of clarified pretreated wastewater was transferred to a stainless steel reaction tank, and micro-nano bubble water was introduced into it using a micro-nano bubble water generator at an air flow rate of 3.0L / min / m 3 The mixture is reacted at 25°C for 15 minutes to form foamy wastewater.

[0054] (3) Flocculation separation: 100L of foamy wastewater was introduced into the solid-liquid separation system through a valve switching, and then 1L of dispersion containing 2g chitosan, 2g corn starch and 2g polyglutamic acid was added. At the same time, 100kHz, 500W ultrasonic treatment was applied for 10min, and the stirring speed was maintained at 150rpm for 30s every 2min during the ultrasonic process. After standing for 10min, air was introduced for air flotation separation for 5min to obtain solid and liquid phases.

[0055] (4) Microbial agent treatment: After air flotation separation, the solid and liquid phases are separated and the liquid phase flows into the sewage treatment plant; the solid is resuspended in deionized water, and compound probiotics are added (addition amount is 10mL / L). After standing at 45℃ for 2h, it is freeze-dried in a freeze dryer to obtain light yellow protein powder. Freezing time is -20℃ and time is 7h.

[0056] Example 3: A biological and environmentally friendly wastewater protein extraction method and its long-term preservation method, the specific steps of which are as follows:

[0057] (1) Pretreatment of cleaning wastewater in production workshop: The cleaning wastewater in production workshop is introduced into a mechanical filtration device, and a stainless steel screen with a pore size of 2mm is used to remove large suspended particles. Then, it is further removed by a polyester precision filter element with a pore size of 150μm to obtain clarified pretreated wastewater.

[0058] (2) Micro-nano bubble enrichment treatment: 100L of clarified pretreated wastewater was transferred to a stainless steel reaction tank, and micro-nano bubble water was introduced into it using a micro-nano bubble water generator with an air flow rate of 5.0L / min / m 3 React at 30°C for 20 minutes to form foamy wastewater;

[0059] (3) Flocculation separation: 100L of foamy wastewater was introduced into the solid-liquid separation system through a valve switching, and then added to a 1L dispersion containing 2.5g chitosan, 2.5g corn starch and 2.5g polyglutamic acid. At the same time, ultrasonic treatment at 150kHz and 1000W was applied for 10min. During the ultrasonic treatment, the stirring speed was maintained at 180rpm for 40s every 3min. After standing for 12min, air was introduced for air flotation separation for 5min to obtain solid and liquid phases.

[0060] (4) Microbial agent treatment: After air flotation separation, the solid and liquid phases are separated and the liquid phase flows into the sewage treatment plant; the solid is resuspended in deionized water, and compound probiotics are added (addition amount is 15mL / L). After standing at 65℃ for 2h, it is freeze-dried in a freeze dryer to obtain light yellow protein powder. Freezing time is -15℃ and time is 8h.

[0061] Comparative Example 1: The difference from Example 2 is that in step (3), chitosan and polyglutamic acid are replaced with corn starch, and the other steps are the same as in Example 2.

[0062] Comparative Example 2: The difference from Example 2 is that in step (2), a micro-nano bubble generator is not used to introduce micro-nano bubble water, and the other steps are the same as in Example 2.

[0063] Comparative Example 3: The difference from Example 2 is that in step (4), a compound probiotic group is not introduced for protein preservation treatment, but freeze-drying is carried out directly. The remaining steps are the same as in Example 2.

[0064] Performance testing

[0065] Protein recovery rate: Three parallel samples of protein samples obtained from the examples and comparative examples were selected; according to GB / T5009.5-2016 "Determination of protein in food (Kjeldahl method)", 0.5g of dry sample was dissolved and the total nitrogen content was determined and converted to protein content. The protein recovery rate was calculated based on the total amount of protein in the wastewater before the reaction.

[0066] Preservative properties and total bacterial count of protein powder: Three parallel samples of protein samples obtained from the examples and comparative examples were selected; the determination was carried out according to GB4789.2-2016 "Food Microbiology Examination: Determination of Total Bacterial Count". The obtained protein powder samples were sealed in non-vacuum polyethylene bags at 30°C and 75% relative humidity and stored at 30°C. After 30 days, the total number of spoilage bacteria was measured.

[0067] Physicochemical properties of protein powder (solubility): Three parallel samples of protein samples from the examples and comparative examples were selected. Solubility: 1.00 g of dried protein powder sample was weighed and dispersed in 100 mL of deionized water to form a suspension. The suspension was placed in a constant temperature shaker at 25°C and 200 rpm for 30 min and then centrifuged. 25 mL of the supernatant was taken into a pre-dried and weighed aluminum box, dried at 105°C for 2 h, cooled to room temperature and weighed, and recorded as m2. The theoretical dry weight of protein powder in the initial supernatant volume was recorded as m1, and its solubility was calculated.

[0068] The results of the above measurements are shown in Table 1.

[0069] Table 1 Performance Test Results

[0070] Protein recovery rate (%) Total bacterial count (CFU / g) Solubility (%) Example 1 72.5 <![CDATA[3.2×10 3 ]]> 85.2 Example 2 81.6 <![CDATA[0.9×10 3 ]]> 88.9 Example 3 78.3 <![CDATA[1.8×10 3 ]]> 87.6 Comparative Example 1 65.2 <![CDATA[2.1×10 3 ]]> 80.4 Comparative Example 2 60.8 <![CDATA[3.0×10 3 ]]> 76.3 Comparative Example 3 78.3 <![CDATA[2.5×10 6 ]]> 77.6

[0071] Data Analysis: Data from Examples 1 to 3 in Table 1 show that the wastewater protein powder prepared by this invention exhibits high protein recovery rate, good solubility, and low total bacterial count, demonstrating the comprehensive advantages of this process in achieving wastewater resource recovery and product quality control. In summary, the method of this invention, through multi-stage filtration, bubble-enhanced dispersion, flocculation-synergistic separation, and probiotic stabilization treatment, enables the protein powder to possess high purity, good activity, and high stability, forming a stable process system suitable for the high-value recovery of protein from industrial wastewater.

[0072] As can be seen from the data in Example 2 and Comparative Example 1 in Table 1, under the same process conditions, the flocculant system using a combination of chitosan and corn starch has better flocculation performance than corn starch alone. This is presumably because chitosan can adsorb negatively charged protein molecules and suspended particles in wastewater, thereby forming a denser floc structure and improving separation efficiency. At the same time, the active groups of chitosan may generate electrostatic and hydrogen bonding interactions with amino or carboxyl groups on the protein surface, making the protein particle size distribution more uniform and thus improving product solubility. In addition, chitosan itself has a certain antibacterial effect, which can delay the growth of microorganisms during storage and indirectly reduce the final total colony count. Therefore, the introduction of chitosan into the flocculant system achieves a dual improvement in protein separation efficiency and product quality, providing a structural optimization direction for wastewater protein extraction.

[0073] As can be seen from the data in Table 1 for Example 2 and Comparative Example 2, the use of micro-nano bubbles has a significant impact on improving separation efficiency during the wastewater protein recovery process. This is presumably because the high specific surface area of ​​micro-nano bubbles promotes protein molecule aggregation and interfacial adsorption in the liquid phase, making it easier for proteins to contact flocculants and form stable precipitates, thereby improving recovery efficiency. Simultaneously, it accelerates oxygen mass transfer and water flow, causing the oxidation of reducing substances and the volatilization of odor components in the system, which helps reduce microbial activity and improve the storage stability of protein powder.

[0074] As can be seen from the data of Example 2 and Comparative Example 3 in Table 1, the addition of compound probiotics mainly affects the freshness of protein powder in the post-processing stage, indicating that the intervention of compound probiotics can significantly inhibit the microbial growth of protein powder during storage. Compound probiotic treatment provides an important biological guarantee for the long-term freshness preservation of wastewater protein in this invention.

[0075] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A biological and environmentally friendly method for the long-term preservation of protein in wastewater, characterized in that, Includes the following steps: S1 Wastewater Pretreatment: The cleaning wastewater from the production workshop is filtered to obtain clarified pretreated wastewater; S2 enrichment treatment: Micro-nano bubble water is introduced into the pretreated wastewater through a micro-nano bubble water generator to form bubble-containing wastewater; S3 Flocculation Separation: After the foamy wastewater enters the solid-liquid separation system, a biological flocculant is added for flocculation, and ultrasonic treatment is applied at the same time. After uniform mixing and static separation, solid and liquid phases are obtained. S4 microbial agent treatment: The resulting liquid phase flows into the sewage treatment plant; the resulting solid protein is fermented with a compound probiotic group and then freeze-dried to obtain light yellow protein powder.

2. The extraction method according to claim 1, characterized in that, The production workshop cleaning drainage mentioned in step S1 refers to the drainage generated during the processing of saltwater or freshwater fish, specifically the cleaning of fish meat, skin, bones, scales, heads, and internal organs.

3. The extraction method according to claim 1, characterized in that, In step S1, the removal of large particulate suspended matter is achieved by using a stainless steel screen with a pore size of 1-2 mm; the removal of fine residue is achieved by using a precision filter element with a pore size of 80-150 μm.

4. The extraction method according to claim 1, characterized in that, The micro-nano bubble water mentioned in step S2 is generated by passing gas through a micro-nano bubble generator. The gas is one, two or more of the following: air, nitrogen, hydrogen, oxygen, ozone, and carbon dioxide.

5. The extraction method according to claim 1, characterized in that, The micro-nano bubble water described in step S2 has a bubble particle size of 50-500 nm.

6. The extraction method according to claim 1, characterized in that, The flow rate of the micro / nano bubble water introduced in step S2 is 1.0-5.0 L / min / m 3 .

7. The extraction method according to claim 1, characterized in that, The ultrasonic frequency in step S3 is 30-150kHz, the ultrasonic power is 50-1000W, and the ultrasonic time is 10min.

8. The extraction method according to claim 1, characterized in that, The bio-flocculator mentioned in step S3 is one, two, or a mixture of two or more of chitosan, starch, and polyglutamic acid.

9. The extraction method according to claim 1, characterized in that, The concentration of the compound probiotic group added in step S4 is 5-15 mL / L.

10. A biological and environmentally friendly wastewater protein, characterized in that, It is extracted by the extraction method described in any one of claims 1-9.

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