A microorganism-surfactant solution and a method and device for producing lactic acid and acetic acid

Abstract

The present invention belongs to the field of biochemical technology, and specifically relates to a microorganism-surfactant solution and a method for producing lactic acid and acetic acid. The present invention provides a microorganism-surfactant solution, comprising a microorganism and a surfactant; the microorganism comprises cellulose-degrading bacteria and / or lactic acid bacteria; the surfactant comprises an alkyl glycoside; and the mass ratio of the microorganism to the surfactant is 1:1. Wherein, lactic acid bacteria produce lactic acid in an anaerobic fermentation system, and cellulose-degrading bacteria produce acetic acid. The surfactant can significantly reduce the surface tension of the liquid in the fermentation system, making it easier for microbial cells to contact the fermentation raw materials, thereby improving the fermentation efficiency. The present invention provides a method for the synchronous and directional production of lactic acid and acetic acid using a solution, wherein variable temperature gradient control and distillation are adopted during the anaerobic fermentation process to achieve directional and efficient synthesis of lactic acid and acetic acid, thereby improving the acid production efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of biochemistry, and in particular relates to a microorganism-surfactant solution and a method for producing lactic acid and acetic acid. Background Art

[0002] There are two main methods for converting agricultural waste into energy: anaerobic fermentation and direct-fired pyrolysis. Anaerobic fermentation is an effective means of increasing the value of agricultural waste. The process involves anaerobic microorganisms degrading organic waste into low-molecular-weight compounds, producing combustible energy gases such as biogas, as well as products rich in effective nutrients and stable humus. Anaerobic fermentation technology offers many advantages, including high energy efficiency, diverse product diversity, and effective waste treatment.

[0003] The principle of anaerobic fermentation to produce acetic acid is that, in an anaerobic environment, microorganisms utilize organic substrates through a process of glycolysis and fermentation. The hydrogen atoms produced by the substrate decomposition combine with carbon dioxide to form acetic acid. During anaerobic fermentation, sugars are broken down into lactic acid and energy by the enzyme lactate dehydrogenase. Lactate dehydrogenase not only catalyzes the conversion of pyruvate to lactic acid during anaerobic fermentation but also supports the continued glycolysis by regenerating NAD+, allowing lactic acid bacteria to continue metabolizing glucose and producing lactic acid in an oxygen-free environment. However, currently, acidification is the second stage of the fermentation process, and the yields of lactic acid and acetic acid during this stage are low. Summary of the Invention

[0004] In view of this, the present invention provides a microorganism-surfactant solution and a method for producing lactic acid and acetic acid, and the production of lactic acid and acetic acid is increased by adding the microorganism-surfactant solution.

[0005] In order to solve the above problems, the present invention provides the following technical solutions:

[0006] The present invention provides a microorganism-surfactant solution, comprising microorganisms and surfactants; the microorganisms include cellulose-degrading bacteria and / or lactic acid bacteria; the surfactant includes alkyl glycoside; and the mass ratio of the microorganisms to the surfactant is 1:1.

[0007] Preferably, when the microorganisms include cellulose-degrading bacteria and lactic acid bacteria, the mass ratio of the cellulose-degrading bacteria to the lactic acid bacteria is (1-2): (1-2).

[0008] The present invention provides a method for synchronously producing lactic acid and acetic acid using a solution, comprising:

[0009] Adding the solution described in the above technical solution during the anaerobic fermentation, hydrolysis and acidification stage of agricultural waste;

[0010] After the hydrolysis and acidification stage is completed, the anaerobic fermentation system undergoes temperature gradient adjustment and distillation.

[0011] Preferably, the variable temperature gradient adjustment includes a medium temperature stage and a high temperature stage; the temperature of the medium temperature stage is 20-40°C; the temperature of the high temperature stage is greater than 40°C and ≤60°C.

[0012] Preferably, the medium temperature stage is maintained for 1 to 2 days; and the high temperature stage is maintained for 1 to 2 days.

[0013] Preferably, the distillation includes a first distillation and a second distillation; the temperature of the first distillation is 115-130°C, and the temperature of the second distillation is 135-145°C.

[0014] Preferably, the total solid mass fraction of the anaerobic fermentation system is 5% to 15%.

[0015] Preferably, the agricultural waste includes one or more of straw, kitchen waste and livestock and poultry manure.

[0016] Preferably, the anaerobic fermentation device used in the method includes a hydrolysis and acidification reactor, a medium-chain fatty acid synthesis reactor and a distillation and collection device; the distillation and collection device is connected between the hydrolysis and acidification reactor and the medium-chain fatty acid synthesis reactor.

[0017] Beneficial effects of the present invention: The present invention provides a microorganism-surfactant solution comprising microorganisms and surfactants; the microorganisms include cellulose-degrading bacteria and / or lactic acid bacteria. The lactic acid bacteria are heterofermentative lactic acid bacteria. Lactic acid bacteria produce lactic acid in an anaerobic fermentation system, significantly increasing lactic acid and acetic acid yields during the hydrolysis and acidification phases. Cellulase produced by the cellulose-degrading bacteria breaks down high-molecular compounds, such as insoluble cellulose, into soluble sugars, such as glucose. These sugars can be further utilized by other microorganisms, increasing acetic acid production during the hydrolysis and acidification phases. Furthermore, cellulose degradation provides a growth substrate for various microorganisms, helping to maintain and increase the diversity of the microbial community in the anaerobic fermentation system. Furthermore, during cellulose decomposition, cellulose may release substances, such as cellobiose and glucose, that may inhibit microbial activity and hinder complete cellulose hydrolysis. Cellulose-degrading bacteria degrade these substances, reducing their negative impact on the anaerobic fermentation system. The production of acid and acetic acid lowers the pH of the fermentation system, further improving acid production efficiency.

[0018] Furthermore, surfactants can significantly reduce the surface tension of the fermentation system liquid, making it easier for microbial cells to come into contact with the fermentation feedstock, thereby improving fermentation efficiency. Surfactants can also act as antimicrobial agents, protecting the activity of enzymes such as carboxymethyl cellulase and lactate dehydrogenase, thereby indirectly increasing the production of acetic and lactic acids.

[0019] The present invention provides a method for the simultaneous production of lactic acid and acetic acid using a solution. A variable temperature gradient is used during anaerobic fermentation to increase the production of lactic acid and acetic acid by cellulose-degrading bacteria, thereby increasing both acetic acid and lactic acid production and improving straw degradation rates. This method also allows for targeted lactic and acetic acid production. Since excessively high volatile fatty acid concentrations can cause product inhibition during the hydrolysis and acidification of agricultural waste, a distillation method is used to remove this volatile fatty acid production inhibition, thereby increasing lactic and acetic acid production.

[0020] It can be seen that the technical solution provided by the present invention can achieve directional and efficient synthesis of lactic acid and acetic acid, thereby improving acid production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments are briefly introduced below.

[0022] Figure 1 Process flow chart for the directional production of lactic acid and acetic acid by coupling cellulose-degrading bacteria and lactic acid bacteria;

[0023] Figure 2 Schematic diagram of the device used in Examples 2 to 4. DETAILED DESCRIPTION

[0024] The present invention provides a microorganism-surfactant solution, comprising microorganisms and surfactants; the microorganisms include cellulose-degrading bacteria and / or lactic acid bacteria; and the mass ratio of the microorganisms to the surfactant is 1:1.

[0025] As an operative embodiment, the surfactant of the present invention may include an alkyl glycoside. The present invention does not specifically limit the source of the alkyl glycoside, and conventional products can be used. The surfactant of the present invention can promote contact between microorganisms and fermentation raw materials, thereby improving fermentation efficiency.

[0026] As an implementation method, the mass ratio of the microorganism to the surfactant is 1:1. The microorganisms of the present invention include cellulose-degrading bacteria and / or lactic acid bacteria; they may also include cellulose-degrading bacteria and lactic acid bacteria. As an implementation method, the mass ratio of the cellulose-degrading bacteria to the lactic acid bacteria of the present invention may be (1-2): (1-2); in a specific embodiment of the present invention, the mass ratio of the cellulose-degrading bacteria to the lactic acid bacteria may be 1:1, 1:2 or 2:1. In an embodiment of the present invention, the cellulose-degrading bacteria is Bacillus cellulolyticus ( Bacillus cellulosilyticus ), numbered GCMCC1.15312, purchased from the China General Microbial Culture Collection. In the embodiment of the present invention, the lactic acid bacteria is Lactobacillus plantarum ( Lactobacillus plantarum), numbered CICC 24936, was purchased from China Industrial Microbiology Culture Collection Center.

[0027] As an practicable method, the method for preparing the microorganism-surfactant solution described in the present invention may include: culturing microorganisms to obtain a culture solution; mixing a surfactant with water to obtain a surfactant solution; and mixing the culture solution and the surfactant solution to obtain a microorganism-surfactant solution. The present invention does not specifically limit the parameters of the mixing; conventional methods can be used. The APG concentration of the microorganism-surfactant solution described in the present invention can be 0.105g / g TSS to 0.250g / g TSS. In specific embodiments of the present invention, the APG concentration of the microorganism-surfactant solution can be 0.105g / g TSS, 0.245g / g TSS, or 0.250g / g TSS.

[0028] The lactic acid bacteria of the present invention produce lactic acid during the hydrolysis and acidification stage, and the cellulose-degrading bacteria can produce acetic acid. At the same time, the cellulase produced by the cellulose-degrading bacteria decomposes high-molecular compounds such as insoluble cellulose into soluble sugars such as glucose. These sugars can be further utilized by other acidifying microorganisms, thereby improving the acid production efficiency of the entire anaerobic fermentation system.

[0029] The present invention provides a method for synchronously producing lactic acid and acetic acid using a solution, comprising:

[0030] Adding the solution described in the above technical solution during the anaerobic fermentation, hydrolysis and acidification stage of agricultural waste;

[0031] After the hydrolysis and acidification stage is completed, the anaerobic fermentation system undergoes temperature gradient adjustment and distillation.

[0032] As an illustrative embodiment, the agricultural waste of the present invention may include one or more of straw, livestock and poultry manure, and food waste. The straw may include one or more of corn straw, wheat straw, rice straw, and cotton straw. The present invention does not specifically limit the source and composition of the straw; conventional straw may be used. The livestock and poultry manure may include cow dung; the present invention does not specifically limit the source of the livestock and poultry manure; conventional livestock and poultry manure may be used. As an illustrative embodiment, when the agricultural waste includes straw and livestock and poultry manure, the TS ratio of the straw to the livestock and poultry manure is preferably (6-7):(4-3). In specific embodiments of the present invention, the TS ratio of the straw to the livestock and poultry manure may be 7:3 or 6:4. As an illustrative embodiment, when the agricultural waste includes straw and food waste, the TS ratio of the food waste to the straw may be 7:3. As an practicable method, the initial carbon-nitrogen ratio of the anaerobic fermentation system after mixing the agricultural waste can be (25-35):1, or can be 25:1. The setting of the carbon-nitrogen ratio is conducive to the fermentation and acid production of the hydrolysis and acid production system.

[0033] The TS ratio specified in the present invention is intended to promote the growth and metabolism of hydrolytic acidogenic microorganisms, maintain the carbon-nitrogen ratio balance of the hydrolytic acidogenic system, promote substrate hydrolysis and acidification, and increase lactic acid and acetic acid production. In the present invention, the agricultural waste and water can be first mixed to obtain a fermentation material; the initial total solids content of the fermentation material can be 5% to 15%, or 10%. In specific embodiments of the present invention, the initial total solids content can be 5%, 7%, 10%, 11%, 13%, or 15%. The total solids content is set to increase acid production.

[0034] As an practicable manner, the present invention can obtain a fermentation system by mixing the fermentation material with the solution described in the above technical solution; the fermentation system is first subjected to hydrolysis and acidification and then to anaerobic fermentation, and the pH value of the hydrolysis and acidification can be 5.0~6.2, or 5.5~6.0; the setting of the pH value can promote efficient hydrolysis and acid production. The pH value of the anaerobic fermentation can be 5.0~6.2, or 5.5~6.0, and the setting of the pH value can promote anaerobic fermentation to produce biogas. The addition amount of the microorganism-surfactant solution of the present invention can be 8%~15% in the fermentation system, or 10%. The technical solution of the solution of the present invention has been discussed above and will not be repeated here.

[0035] As an operative embodiment, after the hydrolysis and acidification stage, the anaerobic fermentation system of the present invention undergoes variable temperature gradient adjustment and distillation, which can be performed simultaneously. The variable temperature gradient adjustment of the present invention is performed in the anaerobic fermentation apparatus. The variable temperature gradient adjustment of the present invention includes a medium temperature stage and a high temperature stage. The temperature of the medium temperature stage can be 20-40°C, or 30-38°C. In specific embodiments of the present invention, the temperature of the medium temperature stage can be 25, 28, 32, 35, 37, or 40°C. After the temperature is raised to the medium temperature stage, the medium temperature stage can be maintained for 1-2 days, or it can be maintained for 1 day before continuing to the high temperature stage. The temperature of the high temperature stage of the present invention can be greater than 40°C and ≤60°C, or it can be 45-57°C. In specific embodiments of the present invention, the temperature of the high temperature stage can be 40, 43, 45, 48, 50, 53, 55, 57, or 60°C. After the temperature is raised to the high temperature stage, the temperature is no longer raised. The high temperature stage of the present invention can be maintained for 1-2 days, or it can be maintained for 1 day. The present invention does not specifically limit the variable temperature gradient adjustment method, and conventional methods can be used. In a specific embodiment of the present invention, the variable temperature gradient adjustment includes a first temperature increase to the medium temperature stage and a second temperature increase to the high temperature stage. As an optional embodiment, the first temperature increase can be increased by 1°C to 5°C every 2 days, or can be increased by 1°C to 5°C every 2 days and by 5°C to 10°C every 2 days to the temperature of the medium temperature stage. In an embodiment of the present invention, the first temperature increase can be increased by 3°C every 2 days to the medium temperature stage. As an optional embodiment, the first temperature increase of the present invention can also be increased by 2~4°C every 2 days and by 5~7°C every 2 days in the medium temperature stage; in an embodiment of the present invention, the first temperature increase is increased by 3°C every 2 days and by 5°C every 2 days to the medium temperature stage.

[0036] The second temperature increase of the present invention can be performed by increasing the temperature by 1°C to 5°C every 2 days, or by alternating between increasing the temperature by 1°C to 5°C every 2 days and increasing the temperature by 5°C to 10°C every 2 days. As an alternative embodiment, the second temperature increase of the present invention can also be performed by increasing the temperature by 3°C every 2 days. As an alternative embodiment, the second temperature increase can also be performed by alternating between increasing the temperature by 3°C every 2 days and increasing the temperature by 5°C every 2 days.

[0037] The "increase of 1°C to 5°C every 2 days" and "increase of 5°C to 10°C every 2 days" mentioned in the present invention both refer to adjusting the temperature every 2 days. After the acidification stage, the volatile fatty acids formed inhibit the anaerobic fermentation system, reducing the production of lactic acid and acetic acid. Therefore, the present invention regulates the production of lactic acid and acetic acid by adjusting the temperature. During the mesophilic stage, cellulose-degrading bacteria produce more acetic acid, while during the high-temperature stage, lactic acid bacteria produce more lactic acid. This increases acetic acid and lactic acid production, improves straw degradation rate, and achieves targeted production of lactic acid and acetic acid.

[0038] As an practicable manner, the distillation of the present invention may include a first distillation and a second distillation; the temperature of the first distillation of the present invention may be 115-130°C, or 122°C; in a specific embodiment of the present invention, the temperature of the first distillation may be 115, 118, 122, 126, 128 or 130°C; the time of the first distillation may be 14-18 minutes, or 15 minutes; since the boiling point of lactic acid is 122°C and the boiling point of acetic acid is 118°C, the temperature of the first distillation is 115-130°C in order to distill lactic acid and acetic acid to synthesize medium-chain fatty acid precursors. The second distillation may be carried out 47-49 hours after the first distillation is completed, or 48 hours after the first distillation is completed. Controlling the time interval between the two distillations can extend the temperature residence time of the first distillation. The temperature of the second distillation of the present invention can be 135°C to 145°C, or 140°C; in a specific embodiment of the present invention, the temperature of the first distillation can be 115, 117, 119, 121, 123, 125, 127 or 130°C. The time of the second distillation can be 135°C, 137°C, 139°C, 141°C, 143°C or 145°C, or 145°C. The second distillation is carried out until all other excess volatile acids are completely evaporated. The second distillation is to distill other volatile acids except acetic acid and lactic acid for biogas production and to increase biogas production. Since excessive concentration of volatile fatty acids in the hydrolysis and acidification process will cause product inhibition, the secondary distillation method is used to remove the inhibition of volatile acid products. The hydrolyzed acidified liquid is distilled through a stepwise distillation process into a distillation collection unit (i.e., a distillation reactor). After distillation, it enters the second phase, producing medium-chain fatty acids. After entering the second phase, the volatile acids lactic acid and acetic acid condense and are collected to serve as substrates for the synthesis of medium-chain fatty acids, providing favorable conditions for anaerobic fermentation of these acids. Other short-chain acids, such as propionic acid, butyric acid, and isovaleric acid, are retained for the next reactor. Temperature control in the fermentation reactor in the acid-producing phase ultimately leads to the targeted production of lactic acid and acetic acid.

[0039] As an practicable embodiment, the fermentation device used in the method provided by the present invention comprises a hydrolysis and acidification reactor, a medium-chain fatty acid synthesis reactor and a distillation and collection device, wherein the distillation and collection device is connected between the hydrolysis and acidification reactor and the medium-chain fatty acid synthesis reactor. Figure 2 , hydrolysis and acidification and anaerobic fermentation after hydrolysis and acidification are carried out in the hydrolysis and acidification reactor; distillation is carried out in the distillation and collection device, and the hydrolysis and acidification liquid enters the synthesis medium-chain fatty acid reactor through the distillation and collection device. The distillation and collection device adjusts different distillation temperatures through synchronous distillation to relieve the inhibition of volatile acid products. In the distillation and collection device of the present invention, the evaporation area of ​​the molecular still is 0.1m 2 , condensation area is 0.2m 2 .

[0040] In the technical solution of the present invention, a two-phase anaerobic fermentation reaction process is selected for the fermentation process, so that solid-liquid separation is achieved, and the pH, ammonia nitrogen, and soluble chemical oxygen demand (SCOD) during the fermentation process are maintained relatively stable, which is beneficial to the fermentation process.

[0041] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0042] Example 1 Preparation of composite bacterial flora

[0043] The cellulose-degrading bacterium, Bacillus cellulolyticus, designated GCMCC 1.15312, was purchased from the China General Microbial Culture Collection. The culture medium of GCMCC 1.15312 was prepared by propagating the strain at 35°C using Dulbecco's filter paper strips for 9–10 days. Filter paper served as the carbon source, and the disintegration of the filter paper was considered the end of the culture. The resulting cellulose-degrading culture medium was designated as Solution A. The composition of the Dulbecco's filter paper strip medium was: 0.5 g NaNO₃, 1.0 g K₂HPO₄, 0.5 g KCl, 0.5 g MgSO₄·7H₂O, 0.005 g FeSO₄·7H₂O, 10 g filter paper, and 1000 mL distilled water. All components except the filter paper were sterilized at high temperature to obtain the sterilized medium. Pretreat the filter paper: Soak in 1% glacial acetic acid for 24 hours, check with iodine solution to ensure the absence of starch, then rinse with 2% sodium bicarbonate (NaHCO₃). After pretreatment, sterilize at 121°C for 20 minutes and dry for later use. Cut the dried filter paper into small strips (1 x 5 cm) and place them in a test tube containing the sterilized culture medium, allowing the filter paper strips to slightly protrude from the culture medium.

[0044] The lactic acid bacteria was Lactobacillus plantarum, numbered CICC 24936, purchased from the China Industrial Microbiology Culture Collection Center;

[0045] MRS medium was modified to increase the carbon source content. The composition of the modified MRS medium is as follows: 20 g glucose, 10 g peptone, 10 g beef extract, 5 g yeast extract, 0.58 g MgSO₄·7H₂O, 0.25 g MnSO₄·4H₂O, 1.0 mL Tween-80, 2 g K₂HPO₄, 2 g sodium acetate, 2 g diammonium hydrogen citrate, and 1000 mL distilled water. This modified MRS medium can increase acid production in CICC 24936.

[0046] Preparation of Lactic Acid Bacteria Liquid: CICC 24936 was inoculated into modified MRS medium and cultured for 36 hours. Incubate at 35°C to obtain the Lactic Acid Bacteria CICC 24936 liquid, designated Solution B.

[0047] Surfactant alkyl polyglycoside (APG) solution:

[0048] Add surfactant APG into water and mix well to obtain APG solution, which is recorded as solution C;

[0049] Solution A and solution B were mixed in a mass ratio of 2:1 to obtain a mixed solution; the mixed solution was then mixed with solution C of equal mass to obtain composite bacterial population 1.

[0050] Solution A and solution B were mixed in a mass ratio of 1:1 to obtain a mixed solution; the mixed solution was then mixed with an equal mass of solution C to obtain composite bacterial community 2.

[0051] Solution A and solution B were mixed in a mass ratio of 1:2 to obtain a mixed solution; the mixed solution was then mixed with solution C of equal mass to obtain composite bacterial population 3.

[0052] The fermentation device used in Examples 2 to 4 is shown in Figure 2 The device consists of a hydrolysis and acidification reactor, a medium-chain fatty acid synthesis reactor and a distillation collection device. A distillation device is connected between the hydrolysis and acidification reactor and the medium-chain fatty acid synthesis reactor. The anaerobic fermentation carried out in the hydrolysis and acidification reactor is the acid production phase, which is the first phase. The anaerobic fermentation carried out in the medium-chain fatty acid synthesis reactor is the medium-chain fatty acid production phase, which is the second phase. The process flow chart of the directional production of lactic acid and acetic acid by coupling cellulose degrading bacteria and lactic acid bacteria is shown in Figure 1 .

[0053] Example 2

[0054] Treatment group:

[0055] Acid-producing phase: Corn straw was dried and pulverized, then mixed with cow dung at a total solids (TS) ratio of 7:3 to produce a mixture with a carbon-nitrogen ratio of 25:1. This mixture was placed in a hydrolysis-acidification reactor, and water was added to produce a fermentation system with a total solids (TS) mass fraction of 10%. The pH of the fermentation system was adjusted to 5.0, and the composite bacterial consortium 1 prepared in Example 1 was added. Composite bacterial consortium 1 contained 0.105 g / g TSS APG, and the amount of composite bacterial consortium 1 added was 10% of the fermentation system volume.

[0056] After the addition of composite bacterial community 1, hydrolysis and acidification of the acid-producing phase begins.

[0057] The pH value of the acid-producing phase was always controlled at 5.0, and the hydraulic retention time was 48 h.

[0058] The reactor volume was 3 L, with an effective volume of 2.4 L (80% of the total volume). Feeding and discharging began on the first day of hydrolysis and acidification, with both daily feed and discharging volumes of 240 mL. Straw and cow dung were mixed at a total solids (TS) ratio of 7:3, and water was added to create a fermentation system with a total solids (TS) mass fraction of 10%. The feed consisted of 240 mL of fermentation system, and the discharging volume was 240 mL of fermentation broth.

[0059] After 5 days of hydrolysis and acidification, the temperature of the acid-generating phase was raised and distillation was carried out in the distillation collection device simultaneously.

[0060] The specific temperature increase is as follows: Medium-temperature stage: Starting from 29°C after acidification, the temperature of the acid-producing phase was increased by 3°C every 48 hours. When the temperature was adjusted to 38°C, the cellulose-degrading bacteria produced more acetic acid, producing 3.0g / L of acetic acid. The medium-temperature stage temperature was raised to 38°C, and the high-temperature stage temperature increase began. During this high-temperature stage, the temperature of the acid-producing phase was increased by 3°C every 48 hours. The temperature continued to rise until it reached 56°C, at which point the lactic acid bacteria produced more lactic acid, producing 6.5g / L of lactic acid. Starting from 29°C, the acetic acid and lactic acid production at each temperature point in the medium-temperature stage and the high-temperature stage are shown in Table 1. The optimal medium-temperature stage temperature was determined to be 38°C based on acetic acid production, and the optimal high-temperature stage temperature was determined to be 56°C based on lactic acid production.

[0061] The distillation process involved two distillations, with the first distillation starting five days after hydrolysis and acidification. Since lactic acid boils at 122°C and acetic acid boils at 118°C, the temperature of the distillation collection device was maintained at 123°C for 15 minutes. 48 hours after the first distillation, the second distillation was initiated, raising the temperature of the distillation collection device to 140°C to remove the remaining volatile acids from the acid-generating phase.

[0062] Production of medium-chain fatty acid phase: All fermentation liquid distilled from the acid-producing phase is collected into a medium-chain fatty acid reactor to produce the medium-chain fatty acid phase. The production of the medium-chain fatty acid phase is a constant temperature fermentation at 55°C, and the pH value of the synthetic medium-chain fatty acid reactor is 5.5.

[0063] Control group: Same as the treatment group, the only difference being that composite bacterial community 1 was not added.

[0064] Acid production efficiency (%) = (the sum of lactic acid and acetic acid produced by the treatment group - the sum of lactic acid and acetic acid produced by the control group) / the sum of lactic acid and acetic acid produced by the control group.

[0065] At the medium temperature stage of 32℃ and the high temperature stage of 50℃, the acid production efficiency of the treatment group increased by 63% compared with the control group.

[0066] At 35℃ in the medium temperature stage and 56℃ in the high temperature stage, the acid production efficiency of the treatment group increased by 78% compared with the control group.

[0067] At 38°C in the mesophilic stage and 59°C in the hyperthermic stage, the treated group increased acid production by 67% compared to the control. Table 1 does not show lactic acid production at 53°C, as the difference in lactic acid concentration between 53°C and 50°C was not significant.

[0068] Table 1 Acetic acid and lactic acid production at various temperature nodes

[0069]

[0070] In summary, the addition of cellulose-degrading bacteria and lactic acid bacteria to the anaerobic fermentation system, temperature regulation combined with distillation operation can increase the amount of acetic acid and lactic acid produced by anaerobic fermentation. The optimal temperature in the mesophilic stage is 38°C for the maximum acetic acid production, and the optimal temperature in the thermophilic stage is 56°C for the maximum lactic acid production.

[0071] Example 3

[0072] Treatment group:

[0073] Acid-generating phase: Corn straw is dried and crushed for later use. Cow dung and corn straw are used as raw materials. Cow dung and straw are mixed at a TS ratio of 6:4 to obtain a mixture with a carbon-nitrogen ratio of 30:1.

[0074] The mixture was placed in a hydrolysis and acidification reactor, and water was added to form a fermentation system. The total solids (TS) mass fraction of the fermentation system was 15%. The pH of the fermentation system was controlled at 5.0, and the composite bacterial consortium 2 prepared in Example 1 was added. Composite bacterial consortium 2 contained 0.245 g / g TSS APG. The amount of composite bacterial consortium 2 added was 10% of the fermentation system volume.

[0075] After the addition of composite bacterial consortium 2, hydrolysis and acidification of the acid-producing phase began.

[0076] The pH value of the acid-producing phase was always controlled at 5.0, and the hydraulic retention time was 36 h.

[0077] The reactor has a volume of 3 L, with an effective volume of 2.4 L (effective volume is 80% of the total volume). Feeding and discharging began on the first day of hydrolysis and acidification, with a daily feed and discharging volume of 240 mL. Straw and cow dung were mixed at a total solids (TS) ratio of 6:4, and water was added to create a fermentation system with a total solids (TS) mass fraction of 10%. The feed was a 6:4 straw to cow dung mixture; the discharging material was the fermentation broth reacting in the fermenter.

[0078] After 5 days of hydrolysis and acidification, the temperature was raised and distillation was carried out simultaneously. The temperature was raised to the acid-generating phase, and the distillation was carried out using a distillation collection device.

[0079] The temperature increase was as follows: The meso-temperature phase: After acidification, the temperature of the acid-producing phase was increased by 3°C every 48 hours, starting at 29°C. When the meso-temperature temperature reached 38°C, cellulose-degrading bacteria produced a high level of acetic acid, generating 2.8 g / L of acetic acid. The meso-temperature phase was then raised to 38°C, and the high-temperature phase began. During this phase, the temperature of the acid-producing phase was increased by 3°C every 48 hours, continuing to rise to 56°C. Lactic acid bacteria produced a high level of lactic acid, generating 6.0 g / L. The hydrolysis-acidification phase lasted from the time the fermentation system was placed in the fermenter until the distillation was completed. The temperature was increased starting at 29°C. The acetic and lactic acid yields at each meso-temperature and high-temperature phase temperature point are shown in Table 2.

[0080] The distillation process was carried out in two steps. The first distillation began five days after hydrolysis and acidification. Since lactic acid has a boiling point of 122°C and acetic acid has a boiling point of 118°C, the temperature of the distillation collection device was maintained at 125°C for 15 minutes. 48 hours after the first distillation, the second distillation was carried out, raising the temperature of the distillation collection device to 140°C to distill out the remaining volatile acids in the acid-generating phase.

[0081] Medium-chain fatty acid phase: All the fermentation liquid distilled from the acid-producing phase is collected into the medium-chain fatty acid reactor to produce the medium-chain fatty acid phase. The production of the medium-chain fatty acid phase is a constant temperature fermentation at a temperature of 55°C, and the pH value of the synthetic medium-chain fatty acid reactor is 5.5.

[0082] Control group: the same as the treatment group, the only difference being that composite bacterial community 2 was not added.

[0083] At the medium temperature stage of 32℃ and the high temperature stage of 50℃, the acid production efficiency of the treatment group increased by 61% compared with the control group.

[0084] At 35℃ in the medium temperature stage and 53℃ in the high temperature stage, the acid production efficiency of the treatment group increased by 62% compared with the control group.

[0085] At 38℃ in the medium temperature stage and 56℃ in the high temperature stage, the acid production efficiency of the treatment group increased by 69% compared with the control group.

[0086] Table 2 Acetic acid and lactic acid production at various temperature nodes

[0087]

[0088] In summary, the addition of cellulose-degrading bacteria and lactic acid bacteria to the anaerobic fermentation system, temperature regulation combined with distillation operation can increase the amount of acetic acid and lactic acid produced by anaerobic fermentation. The optimal temperature in the mesophilic stage is 38°C for the maximum acetic acid production, and the optimal temperature in the thermophilic stage is 56°C for the maximum lactic acid production.

[0089] Example 4

[0090] Treatment group:

[0091] Acid-producing phase: corn straw is dried and crushed and then set aside. Corn straw and restaurant waste are used as raw materials. The straw and restaurant waste are mixed at a TS ratio of 7:3 to obtain a mixture. The carbon-nitrogen ratio of the mixture is 25:1.

[0092] The mixture was placed in a hydrolysis and acidification reactor, and water was added to form a fermentation system. The total solids (TS) mass fraction of the fermentation system was 15%. The pH of the fermentation system was controlled at 5.0, and the composite bacterial consortium 3 prepared in Example 1 was added. Composite bacterial consortium 3 contained 0.250 g / g TSS APG. The amount of composite bacterial consortium 3 added was 10% of the fermentation system volume.

[0093] After the addition of composite bacterial group 3, hydrolysis and acidification of the acid-producing phase began.

[0094] The pH value of the acid-producing phase was always controlled at 5.0, and the hydraulic retention time was 48 h.

[0095] The reactor volume was 3 L, with an effective volume of 2.4 L (80% of the total volume). Feeding and discharging began on the first day of hydrolysis and acidification, with both daily feed and discharging volumes of 240 mL. Corn stover and food waste were mixed at a total solids (TS) ratio of 7:3, and water was added to create a fermentation system with a total solids (TS) mass fraction of 10%. The feed consisted of 240 mL of the fermentation system; the discharging volume consisted of 240 mL of fermentation broth from the fermentation reaction in the fermenter.

[0096] After 5 days of hydrolysis and acidification, the temperature was raised and distillation was carried out simultaneously. The temperature was raised to the acid-generating phase, and the distillation was carried out using a distillation collection device.

[0097] The specific temperature increase is as follows: Medium-temperature stage: After acidification, starting at 29°C, the temperature is raised by 3°C and 5°C every other day. When the temperature is adjusted to 40°C, cellulose-degrading bacteria produce more acetic acid, generating 7.0 g / L of acetic acid. The medium-temperature stage is raised to 40°C, and the high-temperature stage begins. The temperature is raised by 3°C and 5°C every other day. When the temperature reaches 56°C, lactic acid bacteria produce more lactic acid, generating 13.2 g / L of lactic acid. The temperature increases starting at 29°C. The acetic acid and lactic acid yields at each medium-temperature and high-temperature stage temperature point are shown in Table 3. The hydrolysis and acidification stage is from the time the fermented material is placed in the fermentation equipment to the end of distillation.

[0098] The distillation process was carried out in two steps. The first distillation began five days after hydrolysis and acidification. Since lactic acid boils at 122°C and acetic acid boils at 118°C, the temperature of the distillation collection device was maintained at 130°C for 15 minutes. 48 hours after the first distillation, the second distillation was initiated, raising the temperature of the distillation collection device to 145°C to distill off the remaining volatile acids in the acid-generating phase.

[0099] Medium-chain fatty acid phase: All the fermentation liquid distilled from the acid-producing phase is collected into the medium-chain fatty acid reactor to produce the medium-chain fatty acid phase. The production of the medium-chain fatty acid phase is a constant temperature fermentation at a temperature of 55°C, and the pH value of the synthetic medium-chain fatty acid reactor is 5.5.

[0100] Control group: the same as the treatment group, except that composite bacterial community 3 was not added.

[0101] At 32℃ in the medium temperature stage and 48℃ in the high temperature stage, the acid production efficiency of the treated group increased by 65% ​​compared with the control group.

[0102] At 37℃ in the mesothermal stage and 53℃ in the hyperthermal stage, the acid production efficiency of the treated group increased by 70% compared with the control group.

[0103] At 40℃ in the medium temperature stage and 56℃ in the high temperature stage, the acid production efficiency of the treatment group increased by 77% compared with the control group.

[0104] Table 3 Acetic acid and lactic acid production at various temperature nodes

[0105]

[0106] In summary, the addition of cellulose-degrading bacteria and lactic acid bacteria to the anaerobic fermentation system, temperature regulation combined with distillation operation can increase the amount of acetic acid and lactic acid produced by anaerobic fermentation. The optimal temperature in the mesophilic stage is 40°C for the maximum acetic acid production, and the optimal temperature in the high-temperature stage is 56°C for the maximum lactic acid production.

[0107] In summary, the technical solution provided by the present invention can improve the acid production efficiency, the synthesis amount of lactic acid and acetic acid, and the degradation rate of straw.

[0108] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for synchronously producing lactic acid and acetic acid using a microorganism-surfactant solution, characterized in that: It consists of the following steps: A microorganism-surfactant solution is added during the anaerobic fermentation, hydrolysis and acidification stage of agricultural waste; the agricultural waste is corn straw and cow dung; the microorganism-surfactant solution is composed of microorganisms and surfactants; the microorganisms are cellulose-degrading bacteria and lactic acid bacteria; the surfactant is an alkyl glycoside; the mass ratio of the microorganisms to the surfactant is 1:1; the mass ratio of the cellulose-degrading bacteria to the lactic acid bacteria is (1-2):(1-2); the cellulose-degrading bacteria is Bacillus cellulosilyticus, numbered GCMCC1.15312; the lactic acid bacteria is Lactobacillus plantarum, numbered CICC 24936; After the hydrolysis and acidification stage is completed, the anaerobic fermentation system undergoes variable temperature gradient adjustment and distillation; the variable temperature gradient adjustment includes a medium temperature stage and a high temperature stage; the temperature of the medium temperature stage is 20 to 40°C; the temperature of the high temperature stage is greater than 40°C and ≤60°C; the medium temperature stage is maintained for 1 to 2 days; the high temperature stage is maintained for 1 to 2 days; the distillation includes a first distillation and a second distillation; the temperature of the first distillation is 115 to 130°C, and the temperature of the second distillation is 135°C to 145°C; the total solid mass fraction of the anaerobic fermentation system is 5% to 15%.

2. The method according to claim 1, characterized in that The anaerobic fermentation device used in the method comprises a hydrolysis and acidification reactor, a medium-chain fatty acid synthesis reactor and a distillation and collection device; the distillation and collection device is connected between the hydrolysis and acidification reactor and the medium-chain fatty acid synthesis reactor.

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