Method for synthesizing acetic acid from carbon dioxide by using sludge microbial flora

Abstract

The invention discloses a method for synthesizing acetic acid from carbon dioxide by using sludge microbial flora, which comprises the following steps: step 1, inoculation: taking sludge containing acetogenic bacteria as an inoculum, and adding the inoculum into a reactor containing a basic culture medium; step 2, establishing an initial environment: introducing mixed gas for providing a carbon source and an energy source into the reactor, aerating, and replacing air in the reactor; step 3, implementing a nutrition stress stage: after aeration in the step 2 is finished, sealing the reactor, and carrying out constant-temperature culture for 10-15 days; and 4, strengthening culture in a recovery period: after the step 3 is finished, connecting a mixed gas providing a carbon source and an energy source with the reactor, executing periodic constant-temperature culture, and regularly replacing the basic culture medium in the periodic constant-temperature culture process. The method is simple to operate, low in cost and high in acetic acid yield.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of bioengineering technology, in particular to a method for synthesizing acetic acid from carbon dioxide by using a microbial flora in sludge. BACKGROUND

[0002] With the continuous deepening of global industrialization and the large consumption of fossil fuels, the concentration of carbon dioxide (CO2) in the atmosphere continues to rise, and the global climate change caused thereby has become a serious challenge for human society. Under this background, carbon capture and utilization (CCU) technology has been highly valued by countries around the world because of its dual advantages of reducing greenhouse gas emissions while converting CO2 into high-value-added products. Developing efficient CO2 conversion technology not only has important significance for achieving the goal of "carbon neutrality", but also provides a new path for the green and sustainable production of chemical raw materials.

[0003] Among the many CO2 conversion routes, biological catalytic conversion technology exhibits unique advantages due to its mild reaction conditions, environmental friendliness, and strong sustainability. Among them, the Wood-Ljungdahl (W-L) pathway is one of the most efficient biological carbon fixation pathways known. It has been found that acetogenic bacteria existing in complex bacterial flora in sludge can utilize CO2, CO and H2 as substrates for growth and metabolism through the W-L pathway and produce acetic acid.

[0004] Acetic acid, as a key basic chemical raw material, is widely used in many fields such as food, chemical industry, medicine and pesticide. At present, the synthesis of acetic acid in industry mainly relies on chemical processes such as methanol carbonylation, which is usually carried out at high temperature and high pressure, and has problems such as high energy consumption and heavy pollution. Therefore, developing new biological synthesis routes using CO2 as raw material is of great significance for promoting the green transformation of acetic acid production.

[0005] However, there are still many challenges in directly using raw sludge to convert CO2 into acetic acid: the microbial community in natural sludge is complex and not specific in function, and the proportion of bacterial flora that can effectively utilize CO2 to synthesize acetic acid is low; during the cultivation process, the structure of the bacterial flora is easy to be unbalanced, leading to unstable catalytic function; the solubility of CO2 in water is low, and the mass transfer efficiency is poor, which limits the utilization efficiency of microorganisms; the accumulation of metabolic products may inhibit the activity of the bacterial flora, affecting the stability of long-term operation.

[0006] Currently, the culture method for mixed bacteria is mostly adopted by the strategy of continuous optimization, that is, by continuously supplementing nutrients and maintaining the optimal growth conditions to maintain the activity of the bacterial community. However, such a strategy is often difficult to achieve effective enrichment of high-performance functional strains. In recent years, studies have shown that the application of appropriate selection pressure may promote the enrichment of functional bacterial community, but there is still a lack of systematic research and effective methods on how to direct domestication of mixed bacteria with high-efficiency conversion of CO2 to acetic acid through specific culture strategies.

[0007] Therefore, developing a method which is simple to operate, low in cost and capable of efficiently domesticating sludge microbial community and realizing stable and efficient conversion of CO2 to acetic acid has become a technical problem to be solved in the field. Such a technology not only provides a new way for the resource utilization of CO2, but also opens up a new route for the green production of acetic acid, and has important scientific value and application prospect. SUMMARY

[0008] The purpose of the present application is to provide a method for synthesizing acetic acid from carbon dioxide by using sludge microbial community, which overcomes the technical defects in the prior art. The present application is simple to operate, low in cost and high in acetic acid yield.

[0009] The technical scheme adopted to achieve the purpose of the present application is as follows: A method for synthesizing acetic acid from carbon dioxide by using sludge microbial community, comprising the following steps: Step 1, inoculation: inoculating sludge containing acetic acid-producing bacteria into a reactor containing a basic medium; Step 2, initial environment establishment: introducing a mixed gas providing carbon source and energy into the reactor, and performing aeration to replace the air in the reactor; Step 3, implementation of nutritional stress phase: after the aeration of step 2 is completed, the reactor is sealed and incubated at a constant temperature, and the incubation time is 10-15 days; Step 4, recovery period intensive culture: after step 3 is completed, the mixed gas providing carbon source and energy is connected to the reactor, and periodic constant temperature incubation is performed, and the basic medium is replaced periodically during the periodic constant temperature incubation.

[0010] In the above technical scheme, in step 1, the basic medium contains 4.2 g / L NaHCO3, 2.45 g / L NaH2PO4, 4.575 g / L Na2HPO4, 0.13 g / L KCl, 0.31 g / L NH4Cl, 0.5 g / L yeast extract, 10 mL / L vitamin solution, 10 mL / L trace element solution, 1 g / L sodium 2-bromoethyl sulfonate and 0.25 g / L L-type cysteine.

[0011] In the technical scheme, the mixed gas providing carbon source and energy source in the step 1 and the step 4 is a mixed gas composed of CO2 and H2.

[0012] In the technical scheme, the volume fraction of CO2 in the mixed gas is 15%-25%, and the volume fraction of H2 is 75%-85%.

[0013] In the technical scheme, the aeration time in the step 2 is 5-15 minutes, and the flow rate of the aeration gas is 5-10 mL / min.

[0014] In the technical scheme, the temperature of the constant temperature culture in the step 3 and the step 4 is 35±1℃.

[0015] In the technical scheme, the mixed gas is filled into an aluminum foil gas bag in the step 4, and the aluminum foil gas bag is connected with the reactor through a conduit.

[0016] In the technical scheme, the aluminum foil gas bag is replaced every 2 days, and the basic culture medium is replaced every 10 days in the step 4.

[0017] In the technical scheme, the aluminum foil gas bag is replaced after aeration every time the basic culture medium is replaced.

[0018] In the technical scheme, the periodic constant temperature culture lasts for at least 40 days in the step 4.

[0019] Compared with the prior art, the beneficial effects of the present application are: 1. The present application successfully realizes the efficient biological conversion of CO2 to acetic acid by constructing a specific gas environment and a periodic culture strategy, and the acetic acid concentration can be significantly increased from about 200 mg / L to more than 1000 mg / L, thereby providing an effective biological technology path for the resource utilization of CO2.

[0020] 2. The present application innovatively introduces a nutritional stress stage, effectively screens and enriches high-performance strains by interrupting the supply of gas and nutrients for 10-15 days, and the microbial community shows stronger metabolic activity after recovery culture, and the acetic acid yield can be increased to about 2200 mg / L.

[0021] 3. The special basic culture medium formula adopted in the present application effectively inhibits the activity of methanogens in the sludge containing acetic acid-producing bacteria by adding sodium 2-bromoethyl sulfonate, and maintains a suitable oxidation-reduction potential by adding L-type cysteine, thereby creating an optimal growth environment for acetic acid-producing bacteria and significantly improving the reaction selectivity.

[0022] 4. The present application uses cheap and readily available activated sludge as the source of bacterial strains, and combines a simple and easy-to-use gas bag gas supply system, thereby greatly reducing the operation cost and technical threshold, and having good industrial application prospect.

[0023] 5. The mixed microbial flora obtained by the domestication method of the present application has excellent stability and can maintain high-efficiency acetic acid synthesis capacity during long-term culture, laying a foundation for realizing continuous production. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The time course curve of acetic acid concentration change with culture time after introducing nutritional stress for Example 1 of the present application.

[0025] Figure 2 The time course curve of acetic acid concentration change with culture time during the process of using the basic domestication method for Comparative Example 1 of the present application.

[0026] Figure 3 The comparative bar chart of acetic acid final yield at the end of the respective culture period for Example 1 and Comparative Example 1 of the present application. DETAILED DESCRIPTION The present application will be further described in conjunction with specific examples. It should be understood that the specific examples described herein are merely used to explain the present application and are not used to limit the present application.

[0027] Example 1 A method for efficiently synthesizing acetic acid from CO2 by using a sludge microbial flora, the steps of which are as follows: Step one, inoculation: 30 mL of sludge obtained from the return sludge of the secondary sedimentation tank of a municipal wastewater treatment plant is used as inoculum and added to a 125 mL anaerobic bottle containing 70 mL of special basic medium; three parallel samples (A1, A2, A3) are set in this example. The special basic medium comprises 4.2 g / L NaHCO3, 2.45 g / L NaH2PO4, 4.575 g / L Na2HPO4, 0.13 g / L KCl, 0.31 g / L NH4Cl, 0.5 g / L yeast extract, 10 mL / L vitamin solution, 10 mL / L trace element solution, 1 g / L sodium 2-bromoethyl sulfonate and 0.25 g / L L-type cysteine.

[0028] Step two, initial environment establishment: a mixed gas composed of 20% CO2 and 80% H2 (v / v) is introduced into each anaerobic bottle, the gas flow rate is controlled at 5~10 mL / min, and the aeration is continued for 10 minutes to sufficiently replace the headspace in the bottle and establish the initial gas phase environment.

[0029] Step three, nutritional stress phase implementation: immediately after the aeration was finished, the bottle mouth was sealed with a butyl rubber plug to form a strictly closed system. Then the system was placed in a constant temperature shaker incubator at 35 °C and cultured for 12 days at a rotation speed of 120 rpm. All gas and nutrient replenishment was interrupted during this phase to exert selective pressure on the microbial community.

[0030] Step four, recovery phase reinforced culture: after the nutritional stress phase was over, the gas replenishment system was re-established by connecting an aluminum foil gas bag pre-charged with 100 mL of the same mixed gas to the anaerobic bottle through a conduit. Then periodic culture operations were performed, the aluminum foil gas bag was replaced every 2 days, and the culture medium was replaced every 10 days. The bacteria were retained by standing and settling, and 70 mL of supernatant was discarded, and an equal amount of fresh culture medium was added. Before replacing the gas bag each time, the mixed gas composed of 20% CO2 and 80% H2 (v / v) was used for aeration. The above periodic operations were maintained, and the total culture time was 40 days.

[0031] As Figure 1 It can be seen that after the recovery culture after nutritional stress, the microbial community showed significantly enhanced metabolic activity. The acetic acid concentration increased rapidly from the 13th day, and by the end of the culture (39th day), the acetic acid concentrations of the three parallel samples reached 2290 mg / L, 2030 mg / L, and 2177 mg / L, respectively.

[0032] Comparative Example 1 The present embodiment provides a method for synthesizing carbon dioxide into acetic acid by using sludge microbial flora, the steps of which are as follows: Step one, inoculation: 30 mL of sludge was taken from the return sludge of the secondary sedimentation tank of a municipal wastewater treatment plant as inoculum, and was added to a 125 mL anaerobic bottle containing 70 mL of special base medium; three parallel samples (B1, B2, B3) were set in this embodiment. The special base medium comprises: 4.2 g / L NaHCO3, 2.45 g / L NaH2PO4, 4.575 g / L Na2HPO4, 0.13 g / L KCl, 0.31 g / L NH4Cl, 0.5 g / L yeast extract, 10 mL / L vitamin solution, 10 mL / L trace element solution, 1 g / L sodium 2-bromoethyl sulfonate, and 0.25 g / L L-type cysteine.

[0033] Step two, initial environment establishment: a mixed gas composed of 20% CO2 and 80% H2 was introduced into the anaerobic bottle, and aeration was performed at a flow rate of 5-10 mL per minute for 10 minutes to fully replace the headspace in the bottle and establish the initial gas phase environment.

[0034] Step three, closed culture and gas supplement: after the aeration, immediately connect an aluminum foil gas bag pre-filled with 100ml of the same mixed gas to the anaerobic bottle through a conduit to form a closed gas supplement system, and place the whole reaction system in a constant temperature shaker at 35°C and 120rpm for culture; Step four, periodic operation: replace the gas bag every two days and the culture medium every ten days (after replacing the culture medium, first aerate with a mixed gas composed of 20% CO2 and 80% H2, then replace the gas bag), retain the sludge precipitate by static settling, discard 70ml of supernatant, add 70ml of fresh culture medium, and repeat the above steps for continuous culture for 40 days.

[0035] As Figure 2 It can be seen that the acetic acid concentration increased from the 13th day, and by the end of the culture (39th day), the acetic acid concentrations of the three parallel samples reached 1064mg / L, 1124mg / L and 1410mg / L, respectively.

[0036] Comparing Example 1 and Comparative Example 1, the final acetic acid yield of the method based on nutritional stress of Example 1 was significantly higher than that of the basic domestication method of Comparative Example 1.

[0037] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the principles of the present application, several improvements and refinements can be made, and these improvements and refinements should also be considered within the scope of protection of the present application.

Claims

1. A method for synthesizing acetic acid from carbon dioxide using a microbial consortium of sludge, characterized by, The method comprises the following steps: Step 1, inoculation: adding sludge containing acetogenic bacteria as inoculum into a reactor containing base medium; Step 2, initial environment establishment: introducing mixed gas providing carbon source and energy into the reactor, and aerating to replace air in the reactor; Step 3, implementing of the nutritional stress phase: after the aeration of step 2 is completed, sealing the reactor and performing constant temperature culture for 10-15 days; Step 4, recovery period intensive culture: after step 3 is completed, connecting the mixed gas providing carbon source and energy with the reactor, and performing periodic constant temperature culture, and periodically replacing the base medium during the periodic constant temperature culture.

2. The method for synthesizing acetic acid from carbon dioxide using a sludge microbial community according to claim 1, characterized by, In step 1, the base medium contains 4.2 g / L NaHCO3, 2.45 g / L NaH2PO4, 4.575 g / L Na2HPO4, 0.13 g / L KCl, 0.31 g / L NH4Cl, 0.5 g / L yeast extract, 10 mL / L vitamin solution, 10 mL / L trace element solution, 1 g / L sodium 2-bromoethyl sulfonate and 0.25 g / L L-cysteine.

3. The method of claim 1, wherein the sludge microbial community is a microbial community of the genus Clostridium. In step 1 and step 4, the mixed gas providing carbon source and energy is a mixed gas composed of CO2 and H2.

4. The method for synthesizing carbon dioxide into acetic acid using a sludge microbial community according to claim 3, wherein, The volume fraction of CO2 in the mixed gas is 15%-25%, and the volume fraction of H2 is 75%-85%.

5. The method for synthesizing carbon dioxide into acetic acid using a sludge microbial community according to claim 1, characterized in that, In step 2, the aeration time is 5-15 minutes, and the aeration gas flow rate is 5-10 mL / min.

6. The method for synthesizing acetic acid from carbon dioxide using a sludge microbial community according to claim 1, wherein, In step 3 and step 4, the temperature of the constant temperature culture is 35±1℃.

7. The method for synthesizing acetic acid from carbon dioxide using a sludge microbial community according to claim 1, wherein, In step 4, the mixed gas is filled into an aluminum foil gas bag, and the aluminum foil gas bag is connected with the reactor through a conduit.

8. The method of claim 7, wherein the sludge microbial community is a microbial community of the genus Clostridium. In step 4, the aluminum foil gas bag is replaced every 2 days, and the base medium is replaced every 10 days.

9. The method of claim 8, wherein the sludge microbial community is a microbial community of the genus Clostridium. Each time the base medium is replaced, the aluminum foil gas bag is replaced after aeration.

10. The method for synthesizing acetic acid from carbon dioxide using a sludge microbial community according to claim 1, wherein, In step 4, the periodic constant temperature culture lasts for at least 40 days.

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