A method for efficient production of medium-chain fatty acids using anaerobic fermentation of fruit and vegetable organic waste to extend the chain.

Abstract

This invention discloses a method for efficiently producing medium-chain fatty acids using anaerobic fermentation of fruit and vegetable organic waste, comprising: S1: collecting fruit and vegetable organic waste and crushing it to obtain a mixed liquid of fruit and vegetable organic waste; S2: acclimating sludge: taking sludge from a sewage treatment plant, acclimating it, and setting it aside for later use; S3: fermentation treatment: placing the mixed liquid of fruit and vegetable organic waste obtained in S1 into a fermentation container and adding the acclimated sludge, and fermenting in an anaerobic environment; S4: adding the mixed liquid of fruit and vegetable organic waste every 6 days during the reaction period from 0 to 24 days, with a feeding rate of 1 / 3; S5: adding the mixed liquid of fruit and vegetable organic waste every 6 days during the reaction period from 25 to 42 days, with a feeding rate of 1 / 4; S6: adding the mixed liquid of fruit and vegetable organic waste every 6 days during the reaction period from 43 to 60 days, with a feeding rate of 1 / 5; S7: collecting medium-chain fatty acids. This invention makes full use of the organic resources in kitchen waste, achieving deep waste treatment while promoting the production efficiency and yield of medium-chain fatty acids.

Description

Technical Field

[0001] This invention belongs to the field of food waste treatment, and mainly relates to a method for efficiently producing medium-chain fatty acids by extending the anaerobic fermentation chain of fruit and vegetable organic waste. Background Technology

[0002] With rapid economic development and changes in agricultural structure, the consumption of non-renewable fossil fuels is increasing. Over the past 10 years, global fossil fuel consumption has grown at an average annual rate of 1.7%, leading to a serious energy shortage. Developing renewable energy sources to replace fossil fuels and mitigating the adverse effects of fossil fuel consumption on economic development is of great significance.

[0003] Medium-chain fatty acids (MCFAs) are emerging bioenergy substances, a class of saturated fatty acids with 6-12 carbon atoms in their carbon chains, such as hexanoic acid, heptanoic acid, and octanoic acid. MCFAs can be further processed into lubricating oil conditioners, polymer additives, and oil-based coating auxiliaries, offering advantages such as easy separation and purification, high energy density, and high added value. Currently, MCFAs can be obtained through plant extraction, chemical synthesis, and biosynthesis, but these methods often require expensive raw materials and equipment, resulting in high costs. In recent years, some studies have utilized organic waste to synthesize MCFAs via carbon chain extension pathways; however, most studies still require the addition of ethanol, lactic acid, etc., as electron donors, undoubtedly increasing the production cost of MCFAs and hindering the further application of chain extension technology.

[0004] Fruit and vegetable organic waste is a type of organic waste characterized by high water content, high sugar content, and high volatile solids (VS) / total solids (TS) ratio. Its unique properties make it prone to hydrolysis and acidification, producing short-chain fatty acids and lactic acid. Furthermore, my country produces 1.3 × 10⁻⁶ tons of this organic waste annually. 7 Tons of organic waste from fruits and vegetables are generated, but less than 20% of it is properly treated, highlighting the urgent need for resource utilization of this waste. However, further research in the early stages of this invention revealed that the production of medium-chain fatty acids from fruit and vegetable organic waste is easily limited by electron donors, resulting in a rapid slowdown in reaction rate after a period of time, making it impossible to effectively obtain more products. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the prior art by proposing a method for efficiently producing medium-chain fatty acids using anaerobic fermentation of fruit and vegetable organic waste to extend the anaerobic fermentation chain. This invention achieves its purpose as follows: A method for efficiently producing medium-chain fatty acids using anaerobic fermentation of fruit and vegetable organic waste to extend the anaerobic fermentation chain comprises the following steps:

[0006] S1: Collect organic waste from fruits and vegetables, crush it, add water to adjust the total solid content, and obtain a mixed liquid of organic waste from fruits and vegetables;

[0007] S2: Sludge acclimatization: Take sludge from the sewage treatment plant, add culture medium to acclimatize the sludge, and then place it in a 4℃ environment for later use.

[0008] S3: Fermentation treatment: Place the mixed liquid of fruit and vegetable organic waste described in S1 (vL) into fermentation container A, add the acclimated sludge described in S2, adjust the reaction temperature to 35℃ and the pH to 5.5-6.5, and purge with nitrogen to maintain the anaerobic environment in the fermentation container, thereby carrying out fermentation treatment, producing lactic acid to provide electrons for chain elongation reaction, and producing medium-chain fatty acids.

[0009] S4: Reaction chain extension treatment stage 1: During the 0-24 days of the reaction, every 6 days, add the fruit and vegetable organic waste mixture described in S1 to fermentation container A, with a dosing rate of 1 / 3.

[0010] S5: Reaction chain extension treatment stage 2: During the 25-42 days of the reaction, every 6 days, add the fruit and vegetable organic waste mixture described in S1 to fermentation container A, with a dosing rate of 1 / 4.

[0011] S6: Reaction chain extension treatment stage 3: During the 43-60 days of the reaction, every 6 days, add the fruit and vegetable organic waste mixture described in S1 to fermentation container A, with a dosing rate of 1 / 5.

[0012] S7: Collects medium-chain fatty acids.

[0013] Preferably, the total solid content in S1 is adjusted to 35-55 g / L by adding water.

[0014] Preferably, the sludge acclimatization in S2 includes: after standing for 2 days to remove the supernatant, heating the sludge at 105°C for 30 minutes to remove methanogens; adding culture medium, adjusting the pH to 5.3-5.7 after inoculation, purging with nitrogen for 3 minutes to maintain an anaerobic environment, and finally culturing in a constant temperature shaker at 35°C and a rotation speed of 120 r / min for 30-40 days, during which the culture medium is changed regularly.

[0015] Preferably, the culture medium components in S2 include 0.25 g / L NH4Cl, 0.25 g / L L-Cysteine-HCl·H2O, 0.31 g / L K2HPO4, 1 ml / L vitamin solution, 5 g / L sodium 2-bromoethylsulfonate, 20 mM acetic acid, 0.2 g / L MgSO4·7H2O, 0.23 g / L KH2PO4, 1 g / L glucose, 1 ml / L trace element solution, and 4.48 ml / L lactic acid.

[0016] Preferably, the amount of sludge added in S3 is 100-200g.

[0017] This invention discloses a method for efficiently producing medium-chain fatty acids using anaerobic fermentation of fruit and vegetable organic waste, which has the following advantages: ① It combines the acid production from anaerobic fermentation of fruit and vegetable organic waste with the chain extension process, eliminating the need to add ethanol, lactic acid, or other substances as electron donors, thus reducing the production cost of medium-chain fatty acids; ② By changing the dosage ratio of the mixed liquid of fruit and vegetable organic waste at different reaction stages according to the reaction process, the limitation of reaction passivation is effectively overcome, improving the yield and production efficiency of medium-chain fatty acids; ③ It promotes the utilization degree and waste utilization value of fruit and vegetable organic waste. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of a method for efficiently producing medium-chain fatty acids using anaerobic fermentation of organic fruit and vegetable waste, according to the present invention.

[0019] Figure 2 This is a graph showing the change in medium-chain fatty acid content over time in an embodiment of the present invention; wherein... The curve representing the relationship between MCFA concentration and fermentation time for groups with varying dosing rates; The curve representing the relationship between MCFA concentration and fermentation time for the group with no change in dosing rate. Detailed Implementation

[0020] The following examples or implementation methods are intended to further illustrate the purpose, technical solutions, and advantages of the present invention, and are not intended to limit the invention. A method for efficiently producing medium-chain fatty acids using anaerobic fermentation of fruit and vegetable organic waste includes the following steps:

[0021] S1: Collect organic waste from fruits and vegetables, crush it, and add water to adjust the total solid content to obtain a mixed liquid of organic waste from fruits and vegetables; the total solid content is adjusted to 35-55 g / L by adding water.

[0022] S2: Sludge acclimatization: Take sludge from the sewage treatment plant, add culture medium to acclimate the sludge, and place it in a 4℃ environment for later use; the sludge acclimatization includes: after standing for 2 days to remove the supernatant, heating the sludge at 105℃ for 30 minutes to remove methanogenic bacteria; adding culture medium, adjusting the pH to 5.3-5.7 after inoculation, purging nitrogen gas for 3 minutes to maintain an anaerobic environment, and finally culturing it in a constant temperature shaker at 35℃ and a rotation speed of 120r / min for 30-40 days, during which the culture medium is changed regularly. The culture medium components include 0.25 g / L NH4Cl, 0.25 g / L L-Cysteine-HCl·H2O, 0.31 g / L K2HPO4, 1 ml / L vitamin solution, 5 g / L sodium 2-bromoethylsulfonate, 20 mM acetic acid, 0.2 g / L MgSO4·7H2O, 0.23 g / L KH2PO4, 1 g / L glucose, 1 ml / L trace element solution, and 4.48 ml / L lactic acid.

[0023] S3: Fermentation treatment: Place the mixed liquid of fruit and vegetable organic waste described in S1 (vL) into fermentation container A, add 100-200g of acclimatized sludge described in S2, adjust the reaction temperature to 35℃ and the pH to 5.5-6.5, and purge with nitrogen to maintain the anaerobic environment in the fermentation container, thereby carrying out fermentation treatment, producing lactic acid to provide electrons for chain elongation reaction, and producing medium-chain fatty acids;

[0024] S4: Long reaction chain treatment stage 1: During the 0-24 days of the reaction, every 6 days, add the fruit and vegetable organic waste mixture described in S1 to fermentation container A, with a dosing rate of 1 / 3.

[0025] S5: Reaction chain extension treatment stage 2: During the 25-42 days of the reaction, every 6 days, add the fruit and vegetable organic waste mixture described in S1 to fermentation container A, with a dosing rate of 1 / 4.

[0026] S6: Reaction chain extension treatment stage 3: During the 43-60 days of the reaction, every 6 days, add the fruit and vegetable organic waste mixture described in S1 to fermentation container A, with a dosing rate of 1 / 5.

[0027] S7: Collects medium-chain fatty acids.

[0028] Example 1:

[0029] (1) In a 1000mL fermentation flask, add 300g of fruit and vegetable organic waste as the fermentation substrate, and simultaneously add 169g of acclimated sludge at an inoculum ratio of 8:1 (substrate:inoculum) to adjust the TS of the system to 5%. Purge the top air with N2 for 3 minutes to maintain an anaerobic environment. The anaerobic culture temperature is 35℃, and the rotation speed is 120r / min. Adjust the pH of the reaction system to 6.0±0.2 using 3mol / L dilute hydrochloric acid solution and 3mol / L NaOH solution.

[0030] (2) To compensate for the lack of lactic acid (electron donor) in the system, the feed rate was changed periodically to adjust the proportion of components in the system. The reaction was divided into three stages: Stage I: 0-24 days, feed rate 1 / 3, 4 cycles, each cycle lasting 6 days; Stage II: 25-42 days, feed rate changed to 1 / 4, 3 cycles, each cycle lasting 6 days; Stage III: 43-60 days, feed rate changed to 1 / 5, 3 cycles, each cycle lasting 6 days, for a total fermentation period of 60 days.

[0031] (3) After 60 days of fermentation, the highest concentration of medium-chain fatty acids was 19.48 g / L. Compared with the 3.56 g / L obtained by the group with no change in the feeding rate, the content of medium-chain fatty acids increased by 5.5 times. Moreover, compared with the reaction before and after stage II (24-42 days, feeding rate 1 / 4), the content of medium-chain fatty acids increased significantly by 55.06%.

Claims

1. A method for efficiently producing medium-chain fatty acids using anaerobic fermentation of fruit and vegetable organic waste, characterized in that, It includes the following steps: S1: Collect organic waste from fruits and vegetables, crush it, add water to adjust the total solid content to 35-55 g / L, and obtain a mixed liquid of organic waste from fruits and vegetables; S2: Sludge Acclimation: Take sludge from the wastewater treatment plant, let it stand for 2 days to remove the supernatant, then heat the sludge at 105℃ for 30 minutes to remove methanogenic bacteria; add culture medium, the components of which are NH4Cl 0.25g / L, L-Cysteine-HCl·H2O 0.25g / L, K2HPO4 0.31g / L, vitamin solution 1mL / L, 2-bromoethylsulfonic acid sodium 5g / L, acetic acid 20mM, MgSO4·7H2O 0.2g / L, KH2PO4 The solution consisted of 0.23 g / L glucose, 1 g / L trace element solution, 1 ml / L lactic acid, and 4.48 mL / L lactic acid. After inoculation, the pH was adjusted to 5.3-5.7, and nitrogen gas was introduced for 3 min to maintain an anaerobic environment. Finally, the solution was placed in a constant temperature shaker at 35℃ and 120 r / min for 30-40 days, during which the culture medium was changed regularly to obtain acclimatized sludge, which was then stored at 4℃ for later use. S3: Fermentation treatment: The mixed liquid of fruit and vegetable organic waste described in S1 is placed in fermentation container A, and the acclimated sludge described in S2 is added. The amount of acclimated sludge added is such that the mass ratio of total solids of the substrate to total solids of the inoculum is 8:1, and the total solids of the reaction is 5%. The reaction temperature is adjusted to 35°C and the pH is adjusted to 5.5-6.

5. Nitrogen gas is introduced to maintain the anaerobic environment in the fermentation container, thereby carrying out fermentation treatment, producing lactic acid to provide electrons for chain elongation reaction, and producing medium-chain fatty acids; S4: Long reaction chain treatment stage 1: During the 0-24 days of the reaction, every 6 days, add the fruit and vegetable organic waste mixture described in S1 to fermentation container A, with a dosing rate of 1 / 3. S5: Reaction chain extension treatment stage 2: During the 25-42 days of the reaction, every 6 days, add the fruit and vegetable organic waste mixture described in S1 to fermentation container A, with a dosing rate of 1 / 4. S6: Reaction chain extension treatment stage 3: During the 43-60 days of the reaction, every 6 days, add the fruit and vegetable organic waste mixture described in S1 to fermentation container A, with a dosing rate of 1 / 5. S7: Collects medium-chain fatty acids.

2. The method for efficiently producing medium-chain fatty acids using anaerobic fermentation of fruit and vegetable organic waste according to claim 1, characterized in that: The amount of sludge added in S3 is 100-200g.

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