Microorganism-surfactant solution and method and device for producing lactic acid and acetic acid

Abstract

The invention belongs to the technical field of biochemistry, and particularly relates to a microorganism-surfactant solution and a method for producing lactic acid and acetic acid. The invention provides a microorganism-surfactant solution. The microorganism-surfactant solution comprises microorganisms and a surfactant, the microorganisms comprise cellulose degrading bacteria and / or lactic acid bacteria; the surfactant comprises alkyl glycoside; the mass ratio of the microorganisms to the surfactant is 1: 1. Wherein the lactic acid bacteria generate lactic acid in the anaerobic fermentation system, and the cellulose degrading bacteria generate acetic acid. The surface active agent can obviously reduce the surface tension of liquid of a fermentation system, so that microbial cells are easier to contact with fermentation raw materials, and the fermentation efficiency is improved. The invention provides a method for synchronously and directionally producing lactic acid and acetic acid by using a solution, which adopts variable-temperature gradient regulation and distillation in the anaerobic fermentation process to realize directional efficient synthesis of lactic acid and acetic acid and improve 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 ways to utilize agricultural waste for energy: anaerobic fermentation and direct combustion pyrolysis. Anaerobic fermentation is an effective technical means for high-value utilization of agricultural waste. The essence of this method is that anaerobic microorganisms degrade organic waste into low molecular weight compounds, and obtain combustible energy gases such as biogas and products rich in effective nutrients and stable humus during the fermentation process. Anaerobic fermentation technology has many advantages, such as high energy utilization efficiency, product diversification, and good waste treatment effect.

[0003] The principle of anaerobic fermentation to produce acetic acid is that in an anaerobic environment, microorganisms use organic substrates through fermentation and fermentation processes, and combine the hydrogen atoms produced by the decomposition of the substrate with carbon dioxide to produce acetic acid. In the anaerobic fermentation process, sugars are decomposed into lactic acid and energy under the action of lactate dehydrogenase. Lactate dehydrogenase not only catalyzes the reduction of pyruvate to lactic acid in anaerobic fermentation, but also supports the continued glycolysis by regenerating NAD+, allowing lactic acid bacteria to continue to metabolize glucose and produce lactic acid in an anaerobic environment. However, at present, acidification is the second stage of the fermentation process, and the production of lactic acid and acetic acid in the acidification stage is 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 yield 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: 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.

[0006] 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).

[0007] The present invention provides a method for synchronously producing lactic acid and acetic acid by using a solution, comprising: Adding the solution described in the above technical solution during the anaerobic fermentation, hydrolysis and acidification stage of agricultural waste; After the hydrolysis and acidification stage is completed, the anaerobic fermentation system undergoes temperature gradient adjustment and distillation.

[0008] 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.

[0009] Preferably, the medium temperature stage is maintained for 1 to 2 days; and the high temperature stage is maintained for 1 to 2 days.

[0010] 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°C-145°C.

[0011] Preferably, the total solid mass fraction of the anaerobic fermentation system is 5% to 15%.

[0012] Preferably, the agricultural waste includes one or more of straw, kitchen waste and livestock and poultry manure.

[0013] Preferably, 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.

[0014] Beneficial effects of the present invention: 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. Wherein, the lactic acid bacteria are heterofermentative lactic acid bacteria, and the lactic acid bacteria produce lactic acid in the anaerobic fermentation system, which can significantly increase the lactic acid production and acetic acid production in the hydrolysis and acidification stage. The cellulase produced by the cellulose-degrading bacteria decomposes high molecular compounds such as insoluble cellulose into soluble sugars such as glucose, which can be further utilized by other microorganisms to increase the acetic acid production in the hydrolysis and acidification stage. At the same time, the degradation of cellulose provides a growth matrix for a variety of microorganisms, which helps to maintain and increase the diversity of microbial communities in the anaerobic fermentation system, and cellulose may release some substances such as cellobiose and glucose during the decomposition process, which may inhibit the activity of microorganisms and hinder the complete hydrolysis of cellulose, while the cellulose-degrading bacteria reduce their negative impact on the anaerobic fermentation system by degrading these substances. The production of acid and acetic acid reduces the pH value of the fermentation system, further improving the acid production efficiency.

[0015] In addition, surfactants can significantly reduce the surface tension of the fermentation system liquid, making it easier for microbial cells to contact the fermentation raw materials, thereby improving the fermentation efficiency. Surfactants can also act as antimicrobial agents to protect the activity of enzymes such as carboxymethyl cellulase and lactate dehydrogenase, thereby indirectly increasing the production of acetic acid and lactic acid.

[0016] The present invention provides a method for synchronously producing lactic acid and acetic acid by using a solution, wherein a variable temperature gradient is adopted in the anaerobic fermentation process to increase the lactic acid production of cellulose degrading bacteria and the acetic acid production of cellulose degrading bacteria, thereby achieving the effect of increasing the acetic acid and lactic acid production and increasing the straw degradation rate, and producing lactic acid and acetic acid in a directional manner. Since an excessively high concentration of volatile fatty acids in the hydrolysis and acidification process of agricultural waste will cause product inhibition, a distillation method is adopted to remove the inhibition of volatile fatty acid products and increase the production of lactic acid and acetic acid.

[0017] 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, and improve acid production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments are briefly introduced below.

[0019] Figure 1 Process flow chart for the directional production of lactic acid and acetic acid by coupling cellulose-degrading bacteria and lactic acid bacteria; Figure 2 Schematic diagram of the device used in Examples 2 to 4. DETAILED DESCRIPTION

[0020] 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.

[0021] As an practicable manner, the surfactant of the present invention may include an alkyl glycoside, and the present invention has no particular limitation on the source of the alkyl glycoside, and conventional products may be used. The surfactant of the present invention can promote the contact between microorganisms and fermentation raw materials and improve fermentation efficiency.

[0022] 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 implementable 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, purchased from China Industrial Microbiological Culture Collection Center.

[0023] As an practicable manner, the method for preparing the microorganism-surfactant solution of the present invention may include: culturing the microorganism to obtain a culture solution; mixing the surfactant with water to obtain a surfactant solution; mixing the culture solution and the surfactant solution to obtain a microorganism-surfactant solution. The present invention does not specifically limit the mixing parameters, and conventional methods may be used. The APG concentration of the microorganism-surfactant solution of the present invention may be 0.105 g / g TSS to 0.250 g / g TSS. In a specific embodiment of the present invention, the APG concentration of the microorganism-surfactant solution may be 0.105 g / g TSS, 0.245 g / g TSS or 0.250 g / g TSS.

[0024] The lactic acid bacteria of the present invention produce lactic acid in 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.

[0025] The present invention provides a method for synchronously producing lactic acid and acetic acid by using a solution, comprising: Adding the solution described in the above technical solution during the anaerobic fermentation, hydrolysis and acidification stage of agricultural waste; After the hydrolysis and acidification stage is completed, the anaerobic fermentation system undergoes temperature gradient adjustment and distillation.

[0026] As an practicable manner, the agricultural waste of the present invention may include one or more than two of straw, livestock and poultry excrement and food waste; the straw may include one or more than two of corn straw, wheat straw, rice straw and cotton straw; the present invention has no special restrictions on the source and composition of the straw, and conventional straw may be used. The livestock and poultry excrement may include cow dung; the present invention has no special restrictions on the source of the livestock and poultry excrement, and conventional livestock and poultry excrement may be used. As an practicable manner, when the agricultural waste may include straw and livestock and poultry excrement, the TS ratio of the straw and livestock and poultry excrement is preferably (6-7): (4-3); in a specific embodiment of the present invention, the TS ratio of the straw and livestock and poultry excrement may be 7:3 or 6:4. As an practicable manner, when the agricultural waste may include straw and food waste, the TS ratio of the food waste and straw may be 7:3. As an practicable manner, 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 acid production system.

[0027] The TS ratio of the present invention is limited to promote the growth and metabolism of hydrolytic acid-producing microorganisms, maintain the carbon-nitrogen ratio balance of the hydrolytic acid-producing system, promote substrate hydrolysis and acidification, and increase the production of lactic acid and acetic acid. In the present invention, the agricultural waste and water can be first mixed to obtain a fermentation material; the initial total solid content of the fermentation material can be 5% to 15%, or 10%; in a specific embodiment of the present invention, the initial total solid content can be 5%, 7%, 10%, 11%, 13% or 15%. The total solid content is set to increase the acid production.

[0028] 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 scheme of the solution of the present invention has been discussed above and will not be repeated here.

[0029] As an operative mode, after the hydrolysis and acidification stage is completed, the anaerobic fermentation system of the present invention performs variable temperature gradient adjustment and distillation, and variable temperature gradient adjustment and distillation can be performed simultaneously. The variable temperature gradient adjustment of the present invention is performed in an anaerobic fermentation device. 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 a specific embodiment of the present invention, the temperature of the medium temperature stage can be 25, 28, 32, 35, 37 or 40°C; after the present invention is heated to the medium temperature stage, the medium temperature stage can be maintained for 1-2d, or it can be maintained for 1d and then continue to be heated 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 a specific embodiment of the present invention, the temperature of the high temperature stage can be 40, 43, 45, 48, 50, 53, 55, 57 or 60°C. The present invention is heated to the high temperature stage and no longer continues to heat up. The high temperature stage of the present invention can be maintained for 1-2d, or it can be maintained for 1d. 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 by alternating between increasing 1°C to 5°C every 2 days and increasing 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 increased 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 increased by 5°C every 2 days to the medium temperature stage.

[0030] The second temperature increase of the present invention can be increased to the temperature of the high temperature stage by increasing 1°C to 5°C every 2 days or by alternating 1°C to 5°C every 2 days and 5°C to 10°C every 2 days. As an optional embodiment, the second temperature increase of the present invention can also be carried out by increasing 3°C every 2 days. As an optional embodiment, the second temperature increase can also be carried out by alternating 3°C every 2 days and 5°C every 2 days.

[0031] The "increase of 1°C to 5°C every 2 days" and "increase of 5°C to 10°C every 2 days" described in the present invention both refer to adjusting the temperature once every 2 days. After the acidification stage is completed, 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. In the medium temperature stage, cellulose-degrading bacteria produce more acetic acid, and in the high temperature stage, lactic acid bacteria produce more lactic acid, thereby achieving the effect of increasing the production of acetic acid and lactic acid and increasing the straw degradation rate, and achieving the effect of directional production of lactic acid and acetic acid.

[0032] 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 14-18min, or 15min; 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 performed 47-49h after the first distillation is completed, or the second distillation may be performed 48h after the first distillation is completed. Controlling the time interval between the two distillations may 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 performed 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. Through step-by-step distillation, the hydrolyzed acidified liquid enters the distillation collection device (i.e., distillation reactor) for distillation and then enters the second phase to produce medium-chain fatty acids. After the hydrolyzed acidified liquid enters the second phase, the volatile acids lactic acid and acetic acid are condensed and collected as substrates for synthesizing medium-chain fatty acids, providing favorable conditions for anaerobic fermentation of synthetic production of medium-chain fatty acids. Other short-chain acids such as propionic acid, butyric acid, and isovaleric acid are retained in the next reactor. Then, by regulating the temperature of the fermentation reactor in the acid-producing phase, lactic acid and acetic acid are finally produced in a directional manner.

[0033] As an practicable manner, 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, and 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 synthetic 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 distiller is 0.1m 2 , condensation area is 0.2m 2 .

[0034] 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) of the fermentation process are maintained relatively stable, which is beneficial to the fermentation process.

[0035] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0036] Example 1 Preparation of composite bacterial flora The cellulose degrading bacteria is Bacillus cellulolyticus, numbered GCMCC 1.15312, purchased from the China General Microbial Culture Collection; the preparation of the cellulose degrading bacterial solution GCMCC 1.15312 uses Dulbecco's filter paper strip culture medium for bacterial expansion, and is cultured at a constant temperature of 35°C for 9 to 10 days. The filter paper in the culture medium is used as a carbon source, and the disintegration of the filter paper is used as the end of the culture. The cellulose degrading bacterial solution obtained after the culture is recorded as solution A. The composition of the Dulbecco's filter paper strip culture medium is: NaNO3 0.5g, K2HPO4 1.0g, KCl 0.5g, MgSO4· 7H2O 0.5g. FeSO4· 7H2O 0.005g, 10g filter paper and 1000mL distilled water. Except for the filter paper, all other components in the culture medium are sterilized at high temperature to obtain a sterilized culture medium. Pre-treat the filter paper: soak it in 1% glacial acetic acid for 24 hours, check with iodine solution to make sure there is no starch, then rinse it with 2% sodium carbonate solution NaHCO3, sterilize it at 121℃ for 20 minutes, and dry it for later use. Cut the dried filter paper into small strips (1×5cm) and put them into a test tube containing the sterilized culture medium mentioned above, so that the filter paper strips slightly leak out of the culture medium liquid surface.

[0037] The lactic acid bacteria was Lactobacillus plantarum, numbered CICC 24936, purchased from the China Industrial Microbiological Culture Collection Center; The MRS medium was improved to increase the carbon source content in the medium. The composition of the improved MRS medium was as follows: 20 g glucose, 10 g peptone, 10 g beef extract, 5 g yeast powder, 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. The improved MRS medium can increase the acid production of CICC 24936.

[0038] Preparation of lactic acid bacteria liquid: CICC 24936 was inoculated into the modified MRS medium for 36 hours. The culture was cultured at 35°C to obtain the lactic acid bacteria CICC 24936 liquid, which was recorded as solution B. Surfactant Alkyl Glucoside (APG) Solution: Add surfactant APG into water and mix well to obtain APG solution, which is referred to as C solution; Solution A and solution B are mixed in a mass ratio of 2:1 to obtain a mixed solution; the mixed solution is then mixed with solution C of equal mass to obtain composite bacterial community 1.

[0039] Solution A and solution B are mixed in a mass ratio of 1:1 to obtain a mixed solution; the mixed solution is then mixed with solution C of equal mass to obtain composite bacterial community 2.

[0040] Solution A and solution B are mixed in a mass ratio of 1:2 to obtain a mixed solution; the mixed solution is then mixed with solution C of equal mass to obtain composite bacterial community 3.

[0041] 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 .

[0042] Example 2 Treatment Group: Acid-producing phase: corn stalks were dried and crushed, and corn stalks and cow dung were mixed at a total solid (TS) ratio of 7:3 to obtain a mixture with a carbon-nitrogen ratio of 25:1. The mixture was placed in a hydrolysis acidification reactor, and water was added to obtain a fermentation system with a total solid (TS) mass fraction of 10%. The pH value of the fermentation system was regulated at 5.0, and the composite flora 1 prepared in Example 1 was added. The composite flora 1 contained 0.105 g / g TSS APG, and the amount of composite flora 1 added was 10% of the volume of the fermentation system.

[0043] After the addition of composite bacterial community 1, hydrolysis and acidification of the acid-producing phase began.

[0044] The pH value of the acid-producing phase was always controlled at 5.0, and the hydraulic retention time was 48 h.

[0045] The volume of the reactor is 3L, and the effective volume is 2.4L (the effective volume is 80% of the total volume); the feed and discharge start on the first day of hydrolysis and acidification, and the daily feed volume and discharge volume during the hydrolysis and acidification process are both 240mL. Straw and cow dung are mixed at a total solid (TS) ratio of 7:3, and water is added to obtain a fermentation system. The total solid (TS) mass fraction of the fermentation system is 10%, and the feed is 240mL of the fermentation system; the discharge is 240mL of the fermentation liquid obtained by fermentation.

[0046] After 5 days of hydrolysis and acidification, the temperature of the acid-generating phase was raised and distillation was performed in the distillation collection device simultaneously.

[0047] The specific temperature increase is as follows: Medium temperature stage: starting from 29°C after the acidification, the temperature of the acid-producing phase is increased by 3°C every 48 hours. When the temperature is adjusted to 38°C, the cellulose-degrading bacteria produce more acetic acid, generating 3.0 g / L of acetic acid. The medium temperature stage is heated to 38°C, and the high temperature stage is started. The temperature of the acid-producing phase is increased by 3°C every 48 hours during the high temperature stage. The temperature is continued to rise until the temperature reaches 56°C. The lactic acid bacteria produce more lactic acid and generate 6.5 g / L of lactic acid. The temperature is increased from 29°C. The acetic acid and lactic acid production at each medium temperature stage temperature node and high temperature stage temperature node are shown in Table 1. The optimal medium temperature stage temperature is determined to be 38°C based on the acetic acid production, and the optimal high temperature stage temperature is determined to be 56°C based on the lactic acid production.

[0048] The distillation is specifically as follows: a total of two distillations are carried out, and the first distillation is carried out after 5 days of hydrolysis and acidification. Since the boiling point of lactic acid is 122°C and the boiling point of acetic acid is 118°C, the temperature of the distillation collection device is 123°C during the first distillation, and the distillation time is 15 minutes. After the first distillation is completed for 48 hours, the second distillation is started, and the temperature of the distillation collection device is increased to 140°C to distill out the remaining volatile acids in the acid-producing phase.

[0049] Production of medium-chain fatty acid phase: All distilled fermentation liquid from the acid-producing phase is collected in 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.

[0050] Control group: Same as the treatment group, the only difference was that composite flora 1 was not added.

[0051] 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.

[0052] At 32℃ in the medium temperature stage and 50℃ in the high temperature stage, the acid production efficiency of the treatment group increased by 63% compared with the control group.

[0053] 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.

[0054] At 38℃ in the mesophilic stage and 59℃ in the hyperthermic stage, the acid production efficiency of the treatment group increased by 67% compared with the control group. In Table 1, the lactic acid production at 53℃ is not shown in Table 1 because the lactic acid concentration at 53℃ is not much different from that at 50℃.

[0055] Table 1 Acetic acid and lactic acid production at various temperature nodes

[0056] In summary, adding cellulose-degrading bacteria and lactic acid bacteria to the anaerobic fermentation system, and combining temperature regulation 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 high-temperature stage is 56°C for the maximum lactic acid production.

[0057] Example 3 Treatment Group: Acid-producing phase: corn stalks are dried and crushed for later use. Cow dung and corn stalks are used as raw materials, and the cow dung and stalks are mixed at a TS ratio of 6:4 to obtain a mixture, and the carbon-nitrogen ratio of the mixture is 30:1.

[0058] The mixture was placed in a hydrolysis acidification reactor, and water was added to obtain a fermentation system, wherein the total solid (TS) mass fraction of the fermentation system was 15%. The pH value of the fermentation system was regulated at 5.0, and the composite flora 2 prepared in Example 1 was added. The composite flora 2 contained 0.245 g / g TSS APG, and the addition amount of the composite flora 2 was 10% of the volume of the fermentation system.

[0059] After the addition of composite bacterial community 2, hydrolysis and acidification of the acid-producing phase began.

[0060] The pH value of the acid-producing phase was always controlled at 5.0, and the hydraulic retention time was 36 h.

[0061] The volume of the reactor is 3L, and the effective volume is 2.4L (the effective volume is 80% of the total volume); the feed and discharge start on the first day of hydrolysis and acidification, and the daily feed volume and discharge volume during the hydrolysis and acidification process are both 240mL. Straw and cow dung are mixed at a total solid (TS) ratio of 6:4, and water is added to obtain a fermentation system. The total solid (TS) mass fraction of the fermentation system is 10%, and the feed is a 6:4 mixed fermentation system of straw and cow dung; the discharge is the fermentation liquid that is reacting in the fermentation tank.

[0062] 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.

[0063] The specific temperature increase is as follows: Medium temperature stage: starting from 29°C after the acidification, the temperature of the acid-producing phase is increased by 3°C every 48 hours. When the medium temperature is adjusted to 38°C, the cellulose-degrading bacteria produce more acetic acid, generating 2.8 g / L of acetic acid. The medium temperature stage is heated to 38°C, and the high temperature stage is started. The temperature of the acid-producing phase is increased by 3°C every 48 hours. When the temperature continues to rise to 56°C, the lactic acid bacteria produce more lactic acid, generating 6.0 g / L of lactic acid. The hydrolysis and acidification stage is from the time when the fermentation system is placed in the fermentation tank to the end of distillation. The temperature is raised from 29°C, and the acetic acid and lactic acid yields at each medium temperature stage temperature node and high temperature stage temperature node are shown in Table 2.

[0064] The distillation is specifically as follows: a total of two distillations are carried out, and the first distillation is carried out after 5 days of hydrolysis and acidification. Since the boiling point of lactic acid is 122°C and the boiling point of acetic acid is 118°C, the temperature of the distillation collection device is 125°C during the first distillation, and the distillation time is 15 minutes. After the first distillation is completed for 48 hours, the second distillation is started, and the temperature of the distillation collection device is increased to 140°C to distill out the remaining volatile acids in the acid-producing phase.

[0065] Medium-chain fatty acid phase: All the distilled fermentation liquid from the acid-producing phase is collected in 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 55°C, and the pH value of the synthetic medium-chain fatty acid reactor is 5.5.

[0066] Control group: Same as the treatment group, the only difference was that composite flora 2 was not added.

[0067] At 32℃ in the medium temperature stage and 50℃ in the high temperature stage, the acid production efficiency of the treatment group increased by 61% compared with the control group.

[0068] 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.

[0069] 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.

[0070] Table 2 Acetic acid and lactic acid production at each temperature node

[0071] In summary, adding cellulose-degrading bacteria and lactic acid bacteria to the anaerobic fermentation system, and combining temperature regulation 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 high-temperature stage is 56°C for the maximum lactic acid production.

[0072] Example 4 Treatment Group: Acid-producing phase: corn stalks are dried and crushed for later use. Corn stalks and food waste are used as raw materials. The stalks and food waste are mixed at a TS ratio of 7:3 to obtain a mixture. The carbon-nitrogen ratio of the mixture is 25:1.

[0073] The mixture was placed in a hydrolysis acidification reactor, and water was added to obtain a fermentation system, wherein the total solid (TS) mass fraction of the fermentation system was 15%. The pH value of the fermentation system was regulated at 5.0, and the composite flora 3 prepared in Example 1 was added. The composite flora 3 contained 0.250 g / g TSS APG, and the addition amount of the composite flora 3 was 10% of the volume of the fermentation system.

[0074] After the addition of composite bacterial community 3, hydrolysis and acidification of the acid-producing phase began.

[0075] The pH value of the acid-producing phase was always controlled at 5.0, and the hydraulic retention time was 48 h.

[0076] The volume of the reactor is 3L, and the effective volume is 2.4L (the effective volume is 80% of the total volume). Feeding and discharging began on the first day of hydrolysis and acidification, and the daily feed volume and discharging volume during the hydrolysis and acidification process were both 240mL. Corn stalks and kitchen waste were mixed at a total solid (TS) ratio of 7:3, and water was added to obtain a fermentation system. The total solid (TS) mass fraction of the fermentation system was 10%, and the feed was 240mL of the fermentation system; the discharging was 240mL of the fermentation liquid obtained by the fermentation in the fermentation tank.

[0077] 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.

[0078] The specific temperature increase is as follows: Medium temperature stage: starting from 29°C after the acidification, the temperature is raised by 3°C and 5°C every other day. When the temperature is adjusted to 40°C, the cellulose degrading bacteria produce more acetic acid, generating 7.0g / L of acetic acid. The medium temperature stage is heated to 40°C, and the high temperature stage is started. The temperature increase in the high temperature stage is alternating between 3°C and 5°C every other day. When the temperature in the high temperature stage reaches 56°C, the lactic acid bacteria produce more lactic acid, generating 13.2g / L of lactic acid. The temperature is raised from 29°C. The acetic acid and lactic acid yields at each medium temperature stage temperature node and high temperature stage temperature node are shown in Table 3. The hydrolysis acidification stage starts from the placement of the fermented material in the fermentation equipment to the end of distillation.

[0079] The distillation is specifically as follows: a total of two distillations are carried out, and the first distillation is carried out 5 days after hydrolysis and acidification. Since the boiling point of lactic acid is 122°C and the boiling point of acetic acid is 118°C, the temperature of the distillation collection device is 130°C during the first distillation, and the distillation time is 15 minutes. After the first distillation is completed for 48 hours, the second distillation is started, and the temperature of the distillation collection device is increased to 145°C to distill out the remaining volatile acids in the acid-producing phase.

[0080] Medium-chain fatty acid phase: All the distilled fermentation liquid from the acid-producing phase is collected in 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 55°C, and the pH value of the synthetic medium-chain fatty acid reactor is 5.5.

[0081] Control group: Same as the treatment group, the only difference was that composite flora 3 was not added.

[0082] At 32℃ in the medium temperature stage and 48℃ in the high temperature stage, the acid production efficiency of the treatment group increased by 65% ​​compared with the control group.

[0083] At 37℃ in the medium temperature stage and 53℃ in the high temperature stage, the acid production efficiency of the treatment group increased by 70% compared with the control group.

[0084] 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.

[0085] Table 3 Acetic acid and lactic acid production at each temperature node

[0086] In summary, adding cellulose-degrading bacteria and lactic acid bacteria to the anaerobic fermentation system, and combining temperature regulation with distillation operation can increase the amount of acetic acid and lactic acid produced by anaerobic fermentation. The optimal temperature in the medium temperature 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.

[0087] 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 improve the degradation rate of straw.

[0088] Although the above embodiment describes the present invention in detail, 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 protection scope of the present invention.

Claims

1. A microorganism-surfactant solution, characterized in that: It comprises microorganisms and surfactants; the microorganisms comprise cellulose-degrading bacteria and / or lactic acid bacteria; the surfactant comprises alkyl glycoside; and the mass ratio of the microorganisms to the surfactant is 1:

1.

2. The solution according to claim 1, characterized in that 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).

3. A method for synchronously producing lactic acid and acetic acid using a solution, characterized in that: include: Adding the solution of claim 1 or 2 during the anaerobic fermentation, hydrolysis and acidification stage of agricultural waste; After the hydrolysis and acidification stage is completed, the anaerobic fermentation system undergoes temperature gradient adjustment and distillation.

4. The method according to claim 3, characterized in that 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.

5. The method according to claim 4, characterized in that The medium temperature stage is maintained for 1 to 2 days; the high temperature stage is maintained for 1 to 2 days.

6. The method according to claim 3, characterized in that 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°C-145°C.

7. The method according to claim 3, characterized in that The total solid mass fraction of the anaerobic fermentation system is 5%~15%.

8. The method according to claim 3, characterized in that The agricultural waste includes one or more of straw, kitchen waste and livestock and poultry manure.

9. The method according to claim 3, 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.

Images