Method for improving lactic acid production of kitchen garbage by coupling micro-aeration and microbial directional inoculation

Abstract

The application discloses a method for improving lactic acid production of kitchen garbage through micro-aeration and microbial directional inoculation coupling, and belongs to the technical field of kitchen garbage treatment. The method for improving lactic acid production of kitchen garbage comprises the following steps: 1) pretreating kitchen garbage to obtain slurry; 2) performing high-temperature sterilization treatment on the slurry; 3) transferring the sterilized slurry into a reactor to control aeration intensity and aeration load, and inoculating Holtermannia saccardoi spore suspension to perform secondary pretreatment; and 4) adding mixed bacterial agent to the slurry after the secondary pretreatment to perform fermentation and obtain lactic acid. The application develops a process for inoculating efficient functional bacteria for fermentation after aeration and fungal pretreatment, solves the problems of poor stability and low efficiency caused by the dependence of the existing fermentation process on natural flora, and realizes the high efficiency and stability of lactic acid fermentation of kitchen garbage.

Description

Technical Field

[0001] This invention relates to the field of kitchen waste treatment technology, and in particular to a method for enhancing the fermentation and lactic acid production of kitchen waste by coupling micro-aeration and targeted microbial inoculation. Background Technology

[0002] Anaerobic digestion is a core technology for reducing and recycling kitchen waste, converting organic waste into products such as methane, volatile fatty acids, and lactic acid. Lactic acid, as a high-value product and monomer for biodegradable materials, is a key focus of industry research due to its efficient production.

[0003] Recent studies have increasingly demonstrated that microaeration can enhance the performance of anaerobic digestion. In the four stages of anaerobic digestion, microaeration can stimulate hydrolysis and acidification processes. Specifically, it can activate hydrolytic bacterial communities to produce higher levels of extrinsic enzymes, such as amylase, protease, and cellulase, thereby accelerating the breakdown of macromolecular substrates. This enzymatic enhancement increases monomer availability and promotes the production of volatile fatty acids (VFAs) and other fermentation products.

[0004] However, during fermentation, the natural microbial community structure is unstable and easily affected by fluctuations in substrate composition, leading to the easy replacement of the dominant functional bacteria by other bacteria, resulting in large fluctuations in lactic acid yield. Furthermore, lactic acid production is limited by the hydrolysis of organic matter, while fungi, under aerobic conditions, can secrete various extracellular hydrolytic enzymes, including cellulase, amylase, and protease, which can precisely decompose complex organic matter such as starch, protein, and cellulose in kitchen waste. Moreover, under aerobic stimulation, they can accelerate reproduction and enzyme synthesis, allowing the hydrolysis reaction to proceed more efficiently.

[0005] Therefore, this invention develops a process that involves aeration and fungal pretreatment followed by inoculation with highly efficient functional bacteria for fermentation, solving the problems of poor stability and low efficiency caused by the reliance on natural microbial communities in existing fermentation processes, and achieving high efficiency and stability in the lactic acid fermentation of kitchen waste. Summary of the Invention

[0006] The purpose of this invention is to provide a method for enhancing the production of lactic acid from kitchen waste through the coupling of micro-aeration and targeted microbial inoculation, in order to solve the problems existing in the prior art and avoid the problems of poor stability and low efficiency in the fermentation process caused by the variable nature of natural microbial communities.

[0007] To achieve the above objectives, the present invention provides the following solution:

[0008] In a first aspect, the present invention provides a method for enhancing the production of lactic acid from kitchen waste through micro-aeration and targeted inoculation of microorganisms. The method includes the steps of pre-treating kitchen waste to obtain slurry, sterilizing the slurry at high temperature, controlling the aeration intensity and aeration load, inoculating a Holtermannia saccardoi spore suspension for secondary pretreatment, and inoculating a mixed microbial agent after secondary pretreatment for fermentation to obtain lactic acid.

[0009] The mixed bacterial agent is composed of Lactobacillus amylolyticus and Lactobacillus panis in a live bacteria ratio of 9-10:1-2.

[0010] Preferably, the mixed bacterial agent is composed of Lactobacillus amylolyticus and Lactobacillus panis in a live bacteria ratio of 9:1.

[0011] Preferably, the inoculum amount of the mixed microbial agent is 5% v / v.

[0012] Preferably, the inoculum amount of the Holtermannia saccardoi spore suspension is 5% v / v.

[0013] Preferably, the aeration rate is 15 mL / min.

[0014] Preferably, the aeration load is 327 mL air / gVS·L.

[0015] Preferably, the method for obtaining slurry from pretreated kitchen waste is as follows: the collected kitchen waste is crushed, pulped, and centrifuged in three phases to remove grease, impurities, and large solid particles to obtain kitchen waste slurry.

[0016] Preferably, the fermentation temperature is 34-36°C.

[0017] Preferably, the hydraulic retention time during the fermentation process is 3 days.

[0018] The present invention discloses the following technical effects:

[0019] (1) Clarify the combined pretreatment effect of micro-aeration and fungi.

[0020] (2) Targeted inoculation with functional bacteria solves the problem of unstable natural microbial communities in existing technologies. It avoids the defects of microbial community structure being easily affected by substrate composition fluctuations and large fluctuations in lactic acid yield.

[0021] (3) The fermentation system of the present invention has a high lactic acid yield and low cost. It can carry out fermentation under mesophilic conditions of 30~35℃. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 The steady-state product distribution in Example 1;

[0024] Figure 2 The distribution of steady-state products in Comparative Example 1;

[0025] Figure 3 The distribution of steady-state products in Comparative Example 2;

[0026] Figure 4 The distribution of steady-state products in Comparative Example 3. Detailed Implementation

[0027] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0028] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0029] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0030] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0031] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0032] The Holtermannia saccardoi, Lactobacillus amylolyticus, Lactobacillus panis, Lactobacillus amylovorus, and Limosilactobacillus sp. used in the following embodiments and comparative examples of this invention were all commercially available. Holtermannia saccardoi (product number HZB619178) and Limosilactobacillus sp. (product number HZB554533) were purchased from Gray Algae Biotechnology, while Lactobacillus amylolyticus (product number B299446), Lactobacillus panis (product number BMZ012280), and Lactobacillus amylovorus (product number B94633) were purchased from Mingzhou Biotechnology.

[0033] Kitchen waste includes household kitchen waste, restaurant kitchen waste, and other kitchen waste. Pre-treatment of kitchen waste involves crushing, pulping, and three-phase centrifugation to remove grease, impurities, and large solid particles to obtain kitchen waste slurry. These pre-treatment methods are conventional and will not be described in detail here.

[0034] Preparation of Holtermannia saccardoi spore suspension: Holtermannia saccardoi was cultured on potato dextrose agar (PDA) medium at 28°C for 7 days. Conidia were scraped off and suspended in sterile distilled water to prepare a storage suspension (10... 8 (spores / mL), and store at 4℃.

[0035] Example 1

[0036] This embodiment provides a method for optimally enhancing lactic acid production from kitchen waste fermentation by coupling micro-aeration and targeted microbial inoculation. The specific steps are as follows:

[0037] Kitchen waste slurry was sterilized at high temperature (121℃ for 20 minutes). The sterilized slurry was then loaded into a reactor connected to an aeration device and a ceramic aerator. The reactor was connected to a fermentation tank via a peristaltic pump, with an aeration rate of 15 mL / min and a corresponding aeration load of 327 mL air / (gVS·L). Under steady-state conditions, the dissolved oxygen concentration was below 0.5 mg / L. Pretreatment was performed by inoculating with a Holtermannia saccardoi spore suspension. The inoculation amount of the Holtermannia saccardoi spore suspension was 5% (v / v), and the mixture was treated at a constant temperature of 28℃ for 4 days.

[0038] The above substrate was inoculated into the fermentation system, and a mixed inoculum (5% inoculum, v / v) was added. This mixed inoculum consisted of *Lactobacillus amylolyticus* and *Lactobacillus panis* mixed at a viable count ratio of 9:1. The stirring speed was maintained at 60 rpm, the temperature at 35.0 ± 1.0℃, the hRT (heat retention time) was 3 days, and the system was run continuously for 22 days to complete the stable fermentation process.

[0039] Under these conditions, the result is as follows Figure 1 As shown, a large amount of lactic acid rapidly accumulated in the system. Excluding short-term system fluctuations, the lactic acid concentration showed an overall upward trend before reaching steady state, eventually reaching approximately 17676 mg / L. At steady state, the pH was approximately 3.08. Appropriate aeration enhanced the hydrolysis and acidification processes of organic matter, resulting in a more acidic overall fermentation environment. Adding fermentation broth rich in *Lactobacillus amylolyticus* and *Lactobacillus panis* improved the microbial community's tolerance to acidic conditions. Furthermore, treatment with *Holtermannia saccardoi* fungus enhanced the system's uptake and assimilation of carbon substrates.

[0040] Comparative Example 1

[0041] This comparative example provides a method for enhancing the production of lactic acid from kitchen waste through the coupling of micro-aeration and targeted microbial inoculation. The specific steps are as follows:

[0042] Kitchen waste slurry was sterilized at high temperature (121℃ for 20 minutes). The sterilized slurry was then loaded into a reactor connected to an aeration device and a ceramic aerator. The reactor was connected to a fermentation tank via a peristaltic pump, with an aeration rate of 15 mL / min and a corresponding aeration load of 327 mL air / (gVS·L). Under steady-state conditions, the dissolved oxygen concentration was below 0.5 mg / L. Pretreatment was performed by inoculating with a Holtermannia saccardoi spore suspension. The inoculation amount of the Holtermannia saccardoi spore suspension was 5% (v / v), and the mixture was treated at a constant temperature of 28℃ for 4 days.

[0043] The above substrate was inoculated into the fermentation system, and a mixed inoculum (5% inoculum, v / v) was added. The mixed inoculum consisted of *Lactobacillus amylolyticus*, *Lactobacillus panis*, *Lactobacillus amylovorus*, and *Limosilactobacillus sp.* in a viable count ratio of 5:2:2:1. The stirring speed was maintained at 60 rpm, the temperature at 35.0 ± 1.0℃, the hRT (heat recovery time) was 3 days, and the system was run continuously for 22 days to complete the stable fermentation process.

[0044] Under these conditions, the result is as follows Figure 2 As shown, although the lactic acid content generally showed an upward trend, when the system finally reached steady state, the pH stabilized at 3.37 and the lactic acid concentration remained at 15876 mg / L, which was lower than the lactic acid content in Example 1. This may be because after the proportion of Lactobacillus amylolyticus and Lactobacillus panis in the mixed strain decreased, even after treatment with Holtermannia saccardoi fungus, the microorganisms' tolerance to the acidic environment decreased, the acidification rate of the system decreased, and ultimately the lactic acid production decreased.

[0045] Comparative Example 2

[0046] This comparative example provides a method for enhancing the production of lactic acid from kitchen waste through the coupling of micro-aeration and targeted microbial inoculation. The specific steps are as follows:

[0047] Kitchen waste slurry was sterilized at high temperature (121℃ for 20 minutes). The sterilized slurry was then loaded into a reactor connected to an aeration device and a ceramic aerator. The reactor was connected to a fermentation tank via a peristaltic pump, with an aeration rate of 40 mL / min and a corresponding aeration load of 872 mL air / (gVS·L). Under steady-state conditions, the dissolved oxygen concentration was below 0.5 mg / L. Pretreatment was performed by inoculating with a Holtermannia saccardoi spore suspension. The inoculation amount of the Holtermannia saccardoi spore suspension was 5% (v / v), and the mixture was treated at a constant temperature of 28℃ for 4 days.

[0048] The above substrate was inoculated into the fermentation system, and a mixed inoculum (5% inoculum, v / v) was added. This mixed inoculum consisted of *Lactobacillus amylolyticus* and *Lactobacillus panis* mixed at a viable count ratio of 9:1. The stirring speed was maintained at 60 rpm, the temperature at 35.0 ± 1.0℃, the hRT (heat retention time) was 3 days, and the system was run continuously for 22 days to complete the stable fermentation process.

[0049] Under these conditions, the result is as follows Figure 3 As shown, the yield of lactic acid at stable conditions is approximately 10647 mg / L, which is significantly lower than the concentrations of lactic acid and acetic acid in Example 1. Although the hydrolysis rate of the system is similar to that in Example 1 and the microorganisms are more tolerant to the acidic environment, the lactic acid content in the system decreases due to the proliferation of aerobic microorganisms caused by excessive aeration, which consumes organic acids.

[0050] Comparative Example 3

[0051] This comparative example provides a method for enhancing the production of lactic acid from kitchen waste through the coupling of micro-aeration and targeted microbial inoculation. The specific steps are as follows:

[0052] The kitchen waste slurry was sterilized at high temperature (121℃ for 20 minutes). The sterilized kitchen waste slurry raw material was loaded into a reactor connected to an aeration device and a ceramic aerator. The reactor was connected to a fermentation tank through a peristaltic pump. The aeration intensity was 15 mL / min, and the corresponding aeration load was 327 mL air / (gVS·L). Under steady conditions, the dissolved oxygen concentration was less than 0.5 mg / L.

[0053] The above substrate was inoculated into the fermentation system, and a mixed inoculum (5% inoculum, v / v) was added. This mixed inoculum consisted of *Lactobacillus amylolyticus* and *Lactobacillus panis* mixed at a viable count ratio of 9:1. The stirring speed was maintained at 60 rpm, the temperature at 35.0 ± 1.0℃, the hRT (heat retention time) was 3 days, and the system was run continuously for 22 days to complete the stable fermentation process.

[0054] Under these conditions, the result is as follows Figure 4 As shown, a large amount of lactic acid rapidly accumulates in the system. Excluding short-term system fluctuations, the lactic acid content in the system is approximately 13049 mg / L when the steady state is reached. The yield of lactic acid is about 35.5% lower than that in Example 1.

[0055] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for enhancing lactic acid production from kitchen waste through the coupling of micro-aeration and targeted microbial inoculation, characterized in that, The method includes pre-treating kitchen waste to obtain a slurry, sterilizing the slurry at high temperature, controlling the aeration intensity and aeration load, and inoculating. Holtermannia saccardoi The spore suspension undergoes a second pretreatment, followed by inoculation with a mixed bacterial agent for fermentation to obtain lactic acid. The mixed bacterial agent consists of Lactobacillus amyloliquefaciens (Lactobacillus amyloliquefaciens) Lactobacillus amylolyticus Lactobacillus bakerella ( Lactobacillus panis It is prepared by mixing live bacteria in a ratio of 9-10:1-2. The aeration rate is 15 mL / min; The aeration load is 327 mL air / gVS·L; The fermentation temperature is 34-36℃.

2. The method according to claim 1, characterized in that, The mixed bacterial agent consists of Lactobacillus amyloliquefaciens. ( Lactobacillus amylolyticus ), Lactobacillus bakerella ( Lactobacillus panis It is made by mixing live bacteria in a ratio of 9:

1.

3. The method according to claim 2, characterized in that, The inoculation amount of the mixed bacterial agent is 5% v / v.

4. The method according to claim 1, characterized in that, The Holtermannia saccardoi The inoculum size for the spore suspension was 5% v / v.

5. The method according to claim 1, characterized in that, The method for obtaining slurry from pretreated kitchen waste is as follows: the collected kitchen waste is crushed, pulped, and centrifuged in three phases to remove grease, impurities, and large solid particles to obtain kitchen waste slurry.

6. The method according to claim 1, characterized in that, The hydraulic retention time during the fermentation process is 3 days.

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