Method for fermentation treatment of composite wastewater and joint production of single-cell protein

Abstract

The invention discloses a method for fermentation treatment of composite wastewater and joint production of single-cell protein. The method comprises the following steps: (1) carrying out multiplication culture on a microbial strain by using a basic culture medium until the OD600 of fermentation liquor reaches 50-100; and 2) feeding composite wastewater into the fermentation liquid to continue fermentation, stopping fermentation when the volume of the fermentation liquid reaches 2-3 times of the initial volume, and performing solid-liquid separation to obtain single-cell protein. According to the invention, the composite wastewater obtained by compounding two specific process wastewater in a fixed proportion is used as a fermentation raw material, so that the synergistic metabolism of organic matters can be realized to efficiently produce the single-cell protein, the utilization rate of each organic matter component in the wastewater is up to 90% or more, and meanwhile, the biochemical index BOD / COD of the residual fermentation liquor is increased to 0.5 or more.

Description

Technical Field

[0001] This invention relates to methods for treating organic wastewater, and more particularly to a method for fermenting complex wastewater and simultaneously producing single-cell protein. Background Technology

[0002] With the continuous and rapid development of the chemical industry, industrial wastewater with high concentrations of organic matter generated during industrial production has become one of the most serious challenges facing the environmental protection field. This type of industrial wastewater generally has problems such as complex composition, high pollutant concentration, high biological toxicity, and poor biodegradability. Traditional treatment methods are difficult to balance efficiency, cost, and environmental benefits.

[0003] While traditional physicochemical methods can treat such wastewater to some extent, they suffer from high costs and energy consumption, and are prone to generating secondary pollution during the treatment process, making it difficult to achieve both environmental and economic benefits, thus limiting their large-scale application. Biological treatment, on the other hand, has become one of the mainstream research directions and application technologies for industrial wastewater treatment due to its significant advantages such as low cost, ease of operation, and no secondary pollution.

[0004] For industrial wastewater containing organic acids (such as acrylic acid and acetic acid), these organic acids can be used by microorganisms as a carbon source during fermentation. Therefore, utilizing this type of organic wastewater through microbial fermentation is a new solution for treating industrial wastewater.

[0005] For example, patent CN117363499B discloses a method for producing single-cell protein using industrial wastewater and its application. This patent uses industrial wastewater to prepare basal and auxiliary culture media. After fermentation for a specific time, the auxiliary culture media is added, which can efficiently regulate the conversion of organic matter in industrial wastewater into single-cell protein cell growth resources. This combines the treatment of organic wastewater with resource development and utilization, while also increasing the COD degradation rate of industrial wastewater.

[0006] However, taking acrylonitrile process wastewater as an example, it contains high concentrations of cyanide, formaldehyde, acrolein, and other toxic and harmful organic compounds. Among these, highly toxic cyanide has a strong killing effect on microorganisms, and formaldehyde is a recognized highly effective biological inhibitor. Currently, treating this type of cyanide-containing wastewater requires highly efficient physicochemical pretreatment technologies, such as alkaline chlorination oxidation or costly wet air oxidation (WAO), to completely destroy cyanide and partially degrade formaldehyde before biological treatment can proceed. This process is not only energy and chemically demanding and poses a risk of secondary pollution, but also fails to achieve effective resource utilization of organic carbon sources in the wastewater. Furthermore, the production process of the pesticide intermediate methyl-2-(2′-hydroxyphenyl)-3-methoxyacrylate generates process wastewater containing formaldehyde, acetic acid, and methacrylic acid. This wastewater is also of the high COD, highly toxic, and difficult-to-degrade type, with extremely low biodegradability (BOD / COD < 0.35), requiring detoxification and regeneration before treatment.

[0007] The aforementioned patent CN117363499B explored the feasibility of using wastewater from the production of acrylic acid, methyl methacrylate, and polyurethane as a fermentation substrate to produce single-cell protein. The tested examples showed a COD degradation rate of ≥61.4% and a single-cell protein yield of ≥2.11 g / L / h. However, it did not conduct an in-depth study of the effects of formaldehyde and cyanide on the fermentation process. Because a large amount of other organic matter (such as sodium acetate, sodium formate, yeast-based nitrogen source, yeast extract, etc.) is added during fermentation, COD can only characterize the metabolic decomposition of all organic matter before and after fermentation, and cannot characterize the utilization of the original organic matter in the industrial wastewater. Therefore, this invention does not propose a solution on how to eliminate the adverse effects of formaldehyde and cyanide to improve the utilization rate of the original organic matter in the industrial wastewater, thereby reducing the difficulty of subsequent biochemical treatment of the fermentation reaction liquid. Summary of the Invention

[0008] To address the above technical problems, this invention proposes a method for fermenting complex wastewater and simultaneously producing single-cell protein.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A method for fermenting and treating complex wastewater and simultaneously producing single-cell protein includes the following steps:

[0011] 1) Use basal culture medium to proliferate and culture the microbial strains until the fermentation broth reaches OD. 600 Reaching 50-100;

[0012] 2) Add compound wastewater to the fermentation broth and continue fermentation. Stop fermentation when the volume of the fermentation broth reaches 2-3 times the initial volume, and obtain single-cell protein by solid-liquid separation.

[0013] The composite wastewater is a mixture of the first process wastewater and the second process wastewater in a mass ratio of (0.1-5):1, preferably (0.2-3):1, and more preferably (0.3-1):1.

[0014] The first process wastewater contains the following components in the following mass percentages: acrolein 0.01-0.1%, total cyanide 0.1-0.3%, acrylic acid 0.05-0.3%, formaldehyde 0.3-2.0%, and acetic acid 2-5%;

[0015] The second process wastewater contains the following components in the following mass percentages: propionic acid 0.05-0.50%, acrylic acid 0.2-1%, methacrylic acid 0.20-1%, formaldehyde 0.1-1%, and acetic acid 5-10%.

[0016] This invention involves a two-stage fermentation process. Stage one utilizes a basal culture medium to propagate and cultivate microbial strains, enhancing their adaptability to wastewater containing high concentrations of formaldehyde. Stage two involves adding composite wastewater as a carbon source for fermentation to produce single-cell protein. Unexpectedly, this process revealed that the components in the composite wastewater exhibit synergistic metabolic capabilities at specific ratios. This resulted not only in a high yield of single-cell protein but, more importantly, over 90% of the organic matter in the wastewater was utilized efficiently. This significantly improved the biodegradability of the fermentation wastewater, enabling efficient utilization of highly toxic wastewater during fermentation without the need for traditional Fenton oxidation to remove formaldehyde, and reducing the difficulty of subsequent biochemical treatment. This invention not only saves on Fenton oxidation steps but also reduces the difficulty of subsequent biochemical treatment of the fermentation wastewater. In practical industrial applications, the overall production energy consumption is reduced by 30-40% or more.

[0017] In a preferred example, the first process wastewater is acrylonitrile process wastewater;

[0018] Preferably, the second process wastewater is methyl-2-(2′-hydroxyphenyl)-3-methoxyacrylate process wastewater (hereinafter referred to as MHMA process wastewater).

[0019] In a preferred example, in step 1), during the propagation fermentation process, a basic carbon source and optionally a basic nitrogen source are continuously added to meet the propagation and growth requirements of the microbial strain.

[0020] Preferably, the basic carbon source is selected from one or more of glucose, molasses, acetic acid, ethanol, methanol, and starch hydrolysate.

[0021] Preferably, the basic nitrogen source is selected from one or more of ammonia, ammonium sulfate, ammonium nitrate, and ammonium chloride.

[0022] Preferably, in step 1), the pH is adjusted to 5-8 during the fermentation process; the solution used to adjust the pH of the fermentation broth is, for example, one or more of ammonia, sodium hydroxide, potassium hydroxide, and calcium hydroxide.

[0023] When the solution used to adjust the pH of the fermentation broth is ammonia, there is no need to add a basic nitrogen source; simply adjusting the pH to meet the specified range is sufficient to meet the nitrogen source requirements during the propagation fermentation process.

[0024] When the solution used to adjust the pH of the fermentation broth is an alkaline substance other than ammonia, a basic nitrogen source needs to be added to provide sufficient nitrogen for the proliferation fermentation.

[0025] In a preferred embodiment, the basal culture medium comprises: 0.5-5 g / L yeast extract, 1-3 g / L potassium dihydrogen phosphate, 0.1-0.5 g / L potassium sulfate, 0.2-1 g / L magnesium sulfate, 1-3 g / L ammonium sulfate, 0.1-0.5 g / L calcium hydroxide, 1 mL / L trace element stock solution, and 1-10 g / L basic carbon source;

[0026] Preferably, the trace element storage solution comprises the following components: citric acid 0.2-3 g / L, ferrous sulfate heptahydrate 0.5-5 g / L, zinc sulfate heptahydrate 0.1-1 g / L, manganese sulfate monohydrate 0.1-1 g / L, copper sulfate pentahydrate 0.05-0.5 g / L, ammonium molybdate tetrahydrate 0.05-0.5 g / L, cobalt chloride hexahydrate 0.01-0.3 g / L, and boric acid 0.05-0.5 g / L.

[0027] In a preferred example, in step 1), the concentration of the basic carbon source in the fermentation broth is maintained at 1-2 g / L by feeding in a basic carbon source;

[0028] Preferably, in step 1), the concentration of basic nitrogen source in the fermentation broth is maintained at 0-2 g / L, preferably 0.3-1 g / L, by adding basic nitrogen source.

[0029] In a preferred example, the microbial strain is one or more of Candida utilis, Pichia pastoris, Kluyveromyces marxianus, and Yarrowia lipolytica.

[0030] In a preferred example, in step 2), the flow rate of the composite wastewater is 300-1000 g / h to control the acetic acid concentration in the fermentation broth to 1-2 g / L, while the pH is adjusted to 5-8 during the fermentation process.

[0031] In a preferred example, the fermentation conditions in steps 1) and 2) are independent as follows: fermentation temperature 30-37℃, dissolved oxygen concentration 20-30%. The dissolved oxygen concentration can be conventionally adjusted by comprehensively considering factors such as aeration rate, stirring rate, and tank pressure. Preferably, these adjustment conditions are, for example: aeration rate 20-50 L / min, stirring rate 200-800 rpm, and tank pressure 0.05-0.1 MPa (gauge pressure).

[0032] This invention conducts in-depth research on the application of wastewater with different organic compositions in the fermentation production of single-cell protein. It was found that the composite wastewater obtained by combining the aforementioned two specific process wastewaters in a fixed ratio can be synergistically metabolized by microorganisms during fermentation, significantly reducing the biotoxicity of formaldehyde. This not only enables efficient production of single-cell protein, but also achieves a utilization rate of over 90% for each organic component in the wastewater. At the same time, the biodegradability index BOD / COD of the remaining fermentation broth is increased to over 0.5, thus completing this invention. Detailed Implementation

[0033] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

[0034] Unless otherwise specified, the raw materials used in the following embodiments of the present invention can be obtained through conventional commercial purchases. Specifically, the acrylonitrile process wastewater originates from the wastewater generated during the ammoxidation of propylene to produce acrylonitrile; the MHMA process wastewater originates from the wastewater generated during the condensation of salicylaldehyde and diethyl malonate / acetoacetate to produce methyl-2-(2′-hydroxyphenyl)-3-methoxyacrylate. The compositions of each wastewater are as follows:

[0035] Acrylonitrile process wastewater A: Composition includes acrolein 0.05%, total cyanide 0.15%, acrylic acid 0.15%, formaldehyde 1.0%, acetic acid 3.5%, with the balance being water;

[0036] Acrylonitrile process wastewater B: Composition includes acrolein 0.02%, total cyanide 0.1%, acrylic acid 0.06%, formaldehyde 0.3%, acetic acid 4.7%, with the balance being water;

[0037] Acrylonitrile process wastewater C: Composition includes acrolein 0.09%, total cyanide 0.3%, acrylic acid 0.28%, formaldehyde 1.45%, acetic acid 2.5%, with the balance being water.

[0038] MHMA process wastewater A: Composition includes 0.25% propionic acid, 0.6% acrylic acid, 0.6% methacrylic acid, 0.5% formaldehyde, 7.5% acetic acid, with the remainder being water;

[0039] MHMA process wastewater B: Composition includes 0.08% propionic acid, 0.2% acrylic acid, 0.26% methacrylic acid, 0.1% formaldehyde, 9.5% acetic acid, with the remainder being water;

[0040] MHMA process wastewater C: Composition includes 0.45% propionic acid, 0.85% acrylic acid, 0.91% methacrylic acid, 0.89% formaldehyde, 5.2% acetic acid, with the balance being water;

[0041] The performance testing and calculation methods involved in the following embodiments of the present invention are as follows:

[0042] (1) Utilization rate of organic components:

[0043] Headspace gas chromatography method for the detection of organic compounds:

[0044] Chromatographic column: DB-624, dimensions: 30m × 0.32mm × 1.8μm

[0045] Headspace conditions:

[0046] The heating equilibrium temperature is 60-70℃, the equilibrium time is 15-20 min, the injection needle temperature is slightly higher than the heating temperature (75℃), and the transfer line temperature is 90-110℃.

[0047] Gas chromatography conditions:

[0048] Inlet: Split mode, split ratio 10:1 to 20:1, temperature 200℃.

[0049] Carrier gas: high-purity helium (He), constant flow mode, flow rate 1.5-2.0 mL / min.

[0050] Column temperature program: Initial temperature 35℃, hold for 5 min, increase to 120℃ at 10℃ / min, hold for 2 min.

[0051] NPD detector: temperature 250-300℃.

[0052] Utilization rate = (Organic content of raw material wastewater - Organic content of fermentation waste liquid * Volume of fermentation liquid when fermentation stops / Initial volume of fermentation liquid) / Organic content of raw material wastewater

[0053] (2) BOD / COD

[0054] Biochemical oxygen demand (BOD) was tested according to the national standard GB / T 27852-2011, and chemical oxygen demand (COD) was tested according to the national standard GB / T32208-2015. The BOD / COD ratio was calculated to characterize the biodegradability of wastewater. The higher the value, the higher the proportion of easily degradable organic matter.

[0055]

Example 1

[0056] A method for fermenting and treating complex wastewater and simultaneously producing single-cell protein includes the following steps:

[0057] 1) Use basal culture medium to proliferate and culture the microbial strains until the fermentation broth reaches OD. 600 Reaching 75;

[0058] 2) Add compound wastewater to the fermentation broth and continue fermentation. Stop fermentation when the volume of the fermentation broth reaches 2.5 times the initial volume, and obtain single-cell protein by solid-liquid separation.

[0059] The composite wastewater is a mixture of acrylonitrile process wastewater A and MHMA process wastewater A at a mass ratio of 0.5:1.

[0060] In step 1) of this embodiment, the basic culture medium includes: 2 g / L yeast extract, 2.2 g / L potassium dihydrogen phosphate, 0.3 g / L potassium sulfate, 0.5 g / L magnesium sulfate, 2 g / L ammonium sulfate, 0.2 g / L calcium hydroxide, 1 mL / L trace element stock solution, and 2 g / L glucose.

[0061] The trace element storage solution contains the following components: citric acid 1.5 g / L, ferrous sulfate heptahydrate 2.5 g / L, zinc sulfate heptahydrate 0.5 g / L, manganese sulfate monohydrate 0.5 g / L, copper sulfate pentahydrate 0.25 g / L, ammonium molybdate tetrahydrate 0.25 g / L, cobalt chloride hexahydrate 0.15 g / L, boric acid 0.25 g / L, and water to a final volume of 1 L.

[0062] In step 1) of this embodiment, 50wt% glucose is continuously added to meet the requirements for the proliferation and growth of microbial strains, specifically to maintain the glucose concentration in the fermentation broth at 1.5g / L.

[0063] In step 1) of this embodiment, the microbial strain is Candida utilis, and the fermentation conditions are: temperature 33℃, dissolved oxygen concentration 25%, and pH is adjusted to 6.5 with ammonia water during the fermentation process.

[0064] In step 2) of this embodiment, the flow rate of the composite wastewater is 650 g / h to control the acetic acid concentration in the fermentation broth to 1.5 g / L, while ammonia water is used to adjust the pH to 6.5 during the fermentation process.

[0065] In step 2) of this embodiment, the fermentation conditions are: temperature 33℃ and dissolved oxygen concentration 25%.

[0066] Step 2) After fermentation, single-cell protein was obtained by centrifugation (yield DCW 1.5%). The remaining fermentation waste liquid was analyzed for organic matter content, and the utilization rate (%) of each organic component in the wastewater was calculated. At the same time, the BOD / COD value was tested, and the calculation results were summarized in Table 1.

[0067]

Example 2

[0068] A method for fermenting and treating complex wastewater and simultaneously producing single-cell protein includes the following steps:

[0069] 1) Use basal culture medium to proliferate the microbial strains until the OD600 of the fermentation broth reaches 60;

[0070] 2) Add compound wastewater to the fermentation broth and continue fermentation. Stop fermentation when the volume of the fermentation broth reaches 2.3 times the initial volume, and obtain single-cell protein by solid-liquid separation.

[0071] The composite wastewater is a mixture of acrylonitrile process wastewater B and MHMA process wastewater B at a mass ratio of 0.3:1.

[0072] In step 1) of this embodiment, the basic culture medium includes: yeast powder 2.5 g / L, potassium dihydrogen phosphate 2.2 g / L, potassium sulfate 0.3 g / L, magnesium sulfate 0.5 g / L, ammonium sulfate 2.0 g / L, calcium hydroxide 0.2 g / L, trace element stock solution 1 mL / L, and glucose 2.0 g / L;

[0073] The trace element storage solution contains the following components: citric acid 1.5 g / L, ferrous sulfate heptahydrate 2.5 g / L, zinc sulfate heptahydrate 0.5 g / L, manganese sulfate monohydrate 0.5 g / L, copper sulfate pentahydrate 0.25 g / L, ammonium molybdate tetrahydrate 0.25 g / L, cobalt chloride hexahydrate 0.15 g / L, and boric acid 0.25 g / L.

[0074] In step 1) of this embodiment, 50wt% methanol is continuously added to meet the requirements for the proliferation and growth of microbial strains, specifically by maintaining the methanol concentration in the fermentation broth at 1.5g / L.

[0075] In step 1) of this embodiment, the microbial strain is Candida utilis, and the fermentation conditions are: temperature 32℃, dissolved oxygen concentration 25%, and pH is adjusted to 7.0 with ammonia water during the fermentation process.

[0076] In step 2) of this embodiment, the flow rate of the composite wastewater is 600 g / h to control the acetic acid concentration in the fermentation broth to 1.5 g / L, while ammonia water is used to adjust the pH to 7.0 during the fermentation process.

[0077] In step 2) of this embodiment, the fermentation conditions are: temperature 34℃ and dissolved oxygen concentration 23%.

[0078] Step 2) After fermentation, single-cell protein was obtained by centrifugation (yield DCW 4.2%). The remaining fermentation waste liquid was analyzed for organic matter content, and the utilization rate (%) of each organic component in the wastewater was calculated. At the same time, the BOD / COD value was tested, and the calculation results were summarized in Table 1.

[0079]

Example 3

[0080] A method for fermenting and treating complex wastewater and simultaneously producing single-cell protein includes the following steps:

[0081] 1) Use basal culture medium to proliferate the microbial strains until the OD600 of the fermentation broth reaches 80;

[0082] 2) Add compound wastewater to the fermentation broth and continue fermentation. Stop fermentation when the volume of the fermentation broth reaches 2.1 times the initial volume, and obtain single-cell protein by solid-liquid separation.

[0083] The composite wastewater is a mixture of acrylonitrile process wastewater C and MHMA process wastewater C at a mass ratio of 1.5:1.

[0084] In step 1) of this embodiment, the basic culture medium includes: yeast powder 1.8 g / L, potassium dihydrogen phosphate 2.5 g / L, potassium sulfate 0.2 g / L, magnesium sulfate 0.4 g / L, ammonium sulfate 2.5 g / L, calcium hydroxide 0.15 g / L, trace element stock solution 1 mL / L, and starch hydrolysate 3.0 g / L;

[0085] The trace element storage solution contains the following components: citric acid 2.0 g / L, ferrous sulfate heptahydrate 3.0 g / L, zinc sulfate heptahydrate 0.8 g / L, manganese sulfate monohydrate 0.3 g / L, copper sulfate pentahydrate 0.15 g / L, ammonium molybdate tetrahydrate 0.10 g / L, cobalt chloride hexahydrate 0.05 g / L, and boric acid 0.20 g / L.

[0086] In step 1) of this embodiment, 50wt% starch hydrolysate is continuously added to meet the requirements for the proliferation and growth of microbial strains, specifically by maintaining the concentration of starch hydrolysate in the fermentation broth at 1.5g / L.

[0087] In step 1) of this embodiment, the microbial strain is Pichia pastoris, and the fermentation conditions are: temperature 37℃, dissolved oxygen concentration 20%, and pH is adjusted to 7.5 with ammonia water during the fermentation process.

[0088] In step 2) of this embodiment, the flow rate of the composite wastewater is 700 g / h to control the acetic acid concentration in the fermentation broth to 1.8 g / L, while ammonia water is used to adjust the pH to 7.5 during the fermentation process.

[0089] In step 2) of this embodiment, the fermentation conditions are: temperature 30℃ and dissolved oxygen concentration 22%.

[0090] Step 2) After fermentation, single-cell protein was obtained by centrifugation (yield DCW 1.43%). The remaining fermentation waste liquid was analyzed for organic matter content, and the utilization rate (%) of each organic component in the wastewater was calculated. At the same time, the BOD / COD value was tested. The calculation results are summarized in Table 1.

[0091]

Example 4

[0092] A method for fermenting and treating complex wastewater and simultaneously producing single-cell protein includes the following steps:

[0093] 1) Use basal culture medium to proliferate the microbial strains until the OD600 of the fermentation broth reaches 90;

[0094] 2) Add compound wastewater to the fermentation broth and continue fermentation. Stop fermentation when the volume of the fermentation broth reaches 2.6 times the initial volume, and obtain single-cell protein by solid-liquid separation.

[0095] The composite wastewater is a mixture of acrylonitrile process wastewater A and MHMA process wastewater C in a mass ratio of 0.8:1.

[0096] In step 1) of this embodiment, the basic culture medium includes: yeast powder 3.5 g / L, potassium dihydrogen phosphate 1.8 g / L, potassium sulfate 0.4 g / L, magnesium sulfate 0.7 g / L, ammonium sulfate 1.8 g / L, calcium hydroxide 0.30 g / L, trace element stock solution 1 mL / L, and ethanol 4.0 g / L;

[0097] The trace element storage solution contains the following components: citric acid 1.0 g / L, ferrous sulfate heptahydrate 4.0 g / L, zinc sulfate heptahydrate 0.6 g / L, manganese sulfate monohydrate 0.7 g / L, copper sulfate pentahydrate 0.08 g / L, ammonium molybdate tetrahydrate 0.30 g / L, cobalt chloride hexahydrate 0.10 g / L, and boric acid 0.40 g / L.

[0098] In step 1) of this embodiment, 50wt% ethanol is continuously added to meet the requirements for the proliferation and growth of microbial strains, specifically by maintaining the ethanol concentration in the fermentation broth at 1g / L.

[0099] In step 1) of this embodiment, the microbial strain is Kluyveromyces martensii, and the fermentation conditions are: temperature 30℃, dissolved oxygen concentration 20%, and pH is adjusted to 6.0 with ammonia water during the fermentation process.

[0100] In step 2) of this embodiment, the flow rate of the composite wastewater is 900 g / h to control the acetic acid concentration in the fermentation broth to 2 g / L, while ammonia water is used to adjust the pH to 6.0 during the fermentation process.

[0101] In step 2) of this embodiment, the fermentation conditions are: temperature 37°C and dissolved oxygen concentration 26%.

[0102] Step 2) After fermentation, single-cell protein was obtained by centrifugation (yield DCW 1.78%). The remaining fermentation waste liquid was analyzed for organic matter content, and the utilization rate (%) of each organic component in the wastewater was calculated. At the same time, the BOD / COD value was tested. The calculation results are summarized in Table 1.

[0103]

Example 5

[0104] A method for fermenting and treating complex wastewater and simultaneously producing single-cell protein includes the following steps:

[0105] 1) Use basal culture medium to proliferate the microbial strains until the OD600 of the fermentation broth reaches 100;

[0106] 2) Add compound wastewater to the fermentation broth and continue fermentation. Stop fermentation when the volume of the fermentation broth reaches 2.8 times the initial volume, and obtain single-cell protein by solid-liquid separation.

[0107] The composite wastewater is a mixture of acrylonitrile process wastewater B and MHMA process wastewater A in a mass ratio of 5:1.

[0108] In step 1) of this embodiment, the basic culture medium includes: yeast powder 4.0 g / L, potassium dihydrogen phosphate 2.8 g / L, potassium sulfate 0.45 g / L, magnesium sulfate 0.9 g / L, ammonium nitrate 2.2 g / L, calcium hydroxide 0.40 g / L, trace element stock solution 1 mL / L, and acetic acid 3.5 g / L;

[0109] The trace element storage solution contains the following components: citric acid 0.5 g / L, ferrous sulfate heptahydrate 1.5 g / L, zinc sulfate heptahydrate 0.3 g / L, manganese sulfate monohydrate 0.9 g / L, copper sulfate pentahydrate 0.40 g / L, ammonium molybdate tetrahydrate 0.05 g / L, cobalt chloride hexahydrate 0.25 g / L, and boric acid 0.10 g / L.

[0110] In step 1) of this embodiment, 50wt% acetic acid is continuously added to meet the requirements for the proliferation and growth of microbial strains, specifically by maintaining the acetic acid concentration in the fermentation broth at 1.5g / L.

[0111] In step 1) of this embodiment, the microbial strain is Yersinia lipophila, and the fermentation conditions are: temperature 30℃, dissolved oxygen concentration 20%, and pH is adjusted to 6.5 with ammonia water during the fermentation process.

[0112] In step 2) of this embodiment, the flow rate of the composite wastewater is 1000 g / h to control the acetic acid concentration in the fermentation broth to 1.5 g / L, while ammonia water is used to adjust the pH to 6.5 during the fermentation process.

[0113] In step 2) of this embodiment, the fermentation conditions are: temperature 38℃ and dissolved oxygen concentration 28%.

[0114] Step 2) After fermentation, single-cell protein was obtained by centrifugation (yield DCW 2.5%). The remaining fermentation waste liquid was analyzed for organic matter content, and the utilization rate (%) of each organic component in the wastewater was calculated. At the same time, the BOD / COD value was tested, and the calculation results were summarized in Table 1.

[0115]

Example 6

[0116] A method for fermenting and treating complex wastewater and simultaneously producing single-cell protein includes the following steps:

[0117] 1) Use basal culture medium to proliferate the microbial strains until the OD600 of the fermentation broth reaches 50;

[0118] 2) Add compound wastewater to the fermentation broth and continue fermentation. Stop fermentation when the volume of the fermentation broth reaches 3 times the initial volume, and separate the solid and liquid to obtain single-cell protein.

[0119] The composite wastewater is a mixture of acrylonitrile process wastewater B and MHMA process wastewater C in a mass ratio of 2.5:1.

[0120] In step 1) of this embodiment, the basic culture medium includes: yeast powder 1.0 g / L, potassium dihydrogen phosphate 2.0 g / L, potassium sulfate 0.15 g / L, magnesium sulfate 0.3 g / L, ammonium chloride 1.5 g / L, calcium hydroxide 0.10 g / L, trace element stock solution 1 mL / L, and molasses 2.5 g / L;

[0121] The trace element storage solution contains the following components: citric acid 3.0 g / L, ferrous sulfate heptahydrate 0.8 g / L, zinc sulfate heptahydrate 0.1 g / L, manganese sulfate monohydrate 0.2 g / L, copper sulfate pentahydrate 0.50 g / L, ammonium molybdate tetrahydrate 0.45 g / L, cobalt chloride hexahydrate 0.30 g / L, and boric acid 0.50 g / L.

[0122] In step 1) of this embodiment, 50wt% molasses is continuously added to meet the requirements for the proliferation and growth of microbial strains, specifically to maintain the concentration of fermentable sugar in the fermentation broth at 2.5g / L.

[0123] In step 1) of this embodiment, the microbial strain is Yersinia lipophila, and the fermentation conditions are: temperature 32℃, dissolved oxygen concentration 20%, and pH is adjusted to 7.0 with ammonia water during the fermentation process.

[0124] In step 2) of this embodiment, the flow rate of the composite wastewater is 400 g / h to control the acetic acid concentration in the fermentation broth to 2.5 g / L, while ammonia water is used to adjust the pH to 7.0 during the fermentation process.

[0125] In step 2) of this embodiment, the fermentation conditions are: temperature 33℃ and dissolved oxygen concentration 25%.

[0126] Step 2) After fermentation, single-cell protein was obtained by centrifugation (yield DCW 1.75%). The remaining fermentation waste liquid was analyzed for organic matter content, and the utilization rate (%) of each organic component in the wastewater was calculated. At the same time, the BOD / COD value was tested, and the calculation results were summarized in Table 1.

[0127] Comparative Example 1

[0128] Fermentation was carried out in essentially the same manner as in Example 1, except that the composite wastewater was replaced with acrylonitrile process wastewater A.

[0129] Comparative Example 2

[0130] Fermentation was carried out in essentially the same manner as in Example 1, except that the composite wastewater was replaced with MHMA process wastewater A.

[0131] Comparative Example 3

[0132] Fermentation was carried out in essentially the same manner as in Example 1, except that the composite wastewater was a mixture of acrylonitrile process wastewater A and MHMA process wastewater A in a mass ratio of 7:1.

[0133] Table 1

[0134]

[0135] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A method for fermenting and treating complex wastewater and simultaneously producing single-cell protein, characterized in that, Includes the following steps: 1) Use basal culture medium to proliferate and culture the microbial strains until the fermentation broth reaches OD. 600 Reaching 50-100; 2) Add compound wastewater to the fermentation broth and continue fermentation. Stop fermentation when the volume of the fermentation broth reaches 2-3 times the initial volume, and obtain single-cell protein by solid-liquid separation. The composite wastewater is a mixture of the first process wastewater and the second process wastewater in a mass ratio of (0.1-5):1, preferably (0.2-3):1, and more preferably (0.3-1):

1. The first process wastewater contains the following components in the following mass percentages: acrolein 0.01-0.1%, total cyanide 0.1-0.3%, acrylic acid 0.05-0.3%, formaldehyde 0.3-2.0%, and acetic acid 2-5%; The second process wastewater contains the following components in the following mass percentages: propionic acid 0.05-0.50%, acrylic acid 0.2-1%, methacrylic acid 0.20-1%, formaldehyde 0.1-1%, and acetic acid 5-10%.

2. The method for fermenting and treating complex wastewater and jointly producing single-cell protein according to claim 1, characterized in that, The first process wastewater is acrylonitrile process wastewater; Preferably, the second process wastewater is methyl-2-(2′-hydroxyphenyl)-3-methoxyacrylate process wastewater.

3. The method for fermenting and treating complex wastewater and jointly producing single-cell protein according to claim 1, characterized in that, Step 1) During the propagation fermentation process, a basic carbon source and, optionally, a basic nitrogen source are continuously added to meet the propagation and growth requirements of the microbial strain; Preferably, the basic carbon source is selected from one or more of glucose, molasses, acetic acid, ethanol, methanol, and starch hydrolysate. Preferably, the basic nitrogen source is selected from one or more of ammonia, ammonium sulfate, ammonium nitrate, and ammonium chloride; Preferably, the pH is adjusted to 5-8 during the proliferation fermentation process in step 1).

4. The method for fermenting and treating complex wastewater and jointly producing single-cell protein according to any one of claims 1-3, characterized in that, The basic culture medium contains: yeast extract 0.5-5 g / L, potassium dihydrogen phosphate 1-3 g / L, potassium sulfate 0.1-0.5 g / L, magnesium sulfate 0.2-1 g / L, ammonium sulfate 1-3 g / L, calcium hydroxide 0.1-0.5 g / L, trace element stock solution 1 mL / L, and basic carbon source 1-10 g / L; Preferably, the trace element storage solution comprises the following components: Citric acid 0.2-3 g / L, ferrous sulfate heptahydrate 0.5-5 g / L, zinc sulfate heptahydrate 0.1-1 g / L, manganese sulfate monohydrate 0.1-1 g / L, copper sulfate pentahydrate 0.05-0.5 g / L, ammonium molybdate tetrahydrate 0.05-0.5 g / L, cobalt chloride hexahydrate 0.01-0.3 g / L, boric acid 0.05-0.5 g / L.

5. The method for fermenting and treating complex wastewater and jointly producing single-cell protein according to any one of claims 1-4, characterized in that, In step 1), the concentration of basic carbon source in the fermentation broth is maintained at 1-2 g / L by feeding in a basic carbon source; Preferably, in step 1), the concentration of basic nitrogen source in the fermentation broth is maintained at 0-2 g / L by adding basic nitrogen source.

6. The method for fermenting and treating complex wastewater and jointly producing single-cell protein according to any one of claims 1-5, characterized in that, Step 1) The fermentation conditions are: fermentation temperature 30-37℃, dissolved oxygen concentration 20-30%.

7. The method for fermenting and treating complex wastewater and jointly producing single-cell protein according to any one of claims 1-6, characterized in that, The microbial strain is one or more of the following: Candida utilis, Pichia pastoris, Kluyveromyces martensii, and Yersinia lipolytica.

8. The method for fermenting and treating complex wastewater and jointly producing single-cell protein according to any one of claims 1-7, characterized in that, In step 2), the flow rate of the composite wastewater is 300-1000 g / h to control the acetic acid concentration in the fermentation broth to be 1-2 g / L.

9. The method for fermenting and treating complex wastewater and jointly producing single-cell protein according to any one of claims 1-8, characterized in that, The fermentation conditions in step 2) are: fermentation temperature 30-37℃, dissolved oxygen concentration 20-30%, and pH adjusted to 5-8 during fermentation.

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