阅读说明：本技术 利用畜禽粪便发酵液生产中链脂肪酸的方法 (Method for producing medium-chain fatty acid by using livestock and poultry manure fermentation liquor ) 是由 董红敏 张万钦 尹福斌 朱志平 尚斌 曹起涛 陈永杏 于 2019-10-31 设计创作，主要内容包括：本发明属于有机废弃物资源化循环利用领域,涉及一种利用畜禽粪便发酵液生产中链脂肪酸的方法,其包括如下步骤：S1.对接种污泥先进行热处理；S2.在热处理后的接种污泥中加入混合短链脂肪酸溶液；S3.加入乙醇驱动混合短链脂肪酸的碳链延长反应以生产中链脂肪酸。本发明实现了复杂的混合短链脂肪酸在同一开放培养体系中完成多步碳链延长反应,较其他以往研究,该方法可同步生产己酸、庚酸和辛酸等多种中链脂肪酸,且该方法无需灭菌,操作简便,能够适应任意组分比例的短链脂肪酸,得到的己酸、庚酸、辛酸易分离、经济附加值高。(The invention belongs to the field of recycling of organic wastes, and relates to a method for producing medium-chain fatty acid by using livestock and poultry manure fermentation liquor, which comprises the following steps: s1, carrying out heat treatment on the seeded sludge; s2, adding a mixed short-chain fatty acid solution into the thermally-treated inoculated sludge; s3, adding ethanol to drive the carbon chain of the mixed short-chain fatty acid to perform an elongation reaction so as to produce the medium-chain fatty acid. Compared with other previous researches, the method can synchronously produce various medium-chain fatty acids such as caproic acid, heptanoic acid and octanoic acid, does not need sterilization, is simple and convenient to operate, can adapt to short-chain fatty acids with any component proportion, and can obtain caproic acid, heptanoic acid and octanoic acid which are easy to separate and have high economic added value.)

1. A method for producing medium-chain fatty acid by using livestock and poultry manure fermentation liquor is characterized by comprising the following steps:

s1, carrying out heat treatment on the seeded sludge; the heat treatment is heating in water bath at 85 ℃ for 3-5 h;

s2, adding a mixed short-chain fatty acid solution into the thermally-treated inoculated sludge;

s3, adding ethanol to drive the carbon chain extension reaction of the mixed short-chain fatty acid to produce the medium-chain fatty acid, controlling the pH value in the process of the carbon chain extension reaction to be 6.5-7.0, and determining the addition amount of the ethanol based on the molar ratio of the ethanol to the short-chain fatty acid (2-5): 1.

2. The method for producing medium-chain fatty acids using livestock and poultry manure fermentation broth as claimed in claim 1, wherein the ethanol is added in an amount of 2:1 based on the molar ratio of ethanol/short-chain fatty acids.

Technical Field

The invention belongs to the field of recycling of organic wastes, and particularly relates to a method for producing medium-chain fatty acid by using livestock and poultry manure fermentation liquor.

Background

Short-chain fatty acids are key intermediate metabolites in the anaerobic digestion process of organic wastes, and can be used for producing biogas on one hand and synthesizing high-value-added medium-chain fatty acids through reverse beta oxidation (carbon chain extension reaction) on the other hand. Medium chain fatty acids, relative to short chain fatty acids, are an important carboxylic acid platform compound with the following characteristics: (1) the solubility in water is relatively low (less than or equal to 1 percent), and the separation and extraction are easy; (2) the intermediate-chain fatty acid can be used as a precursor for synthesizing biofuel, and is reported to be converted into linear alkane of C6-C12 by Kolbe decarboxylation reaction and used as aviation fuel oil; (3) has important application in rubber, resin synthesis industry, biological bacteriostatic agent and pharmaceutical industry, and can be used for synthesizing spice in food industry, etc.

In recent years, the production of medium chain fatty acids by anaerobic fermentation processes has received increasing attention. Under the drive of an electron donor, short-chain fatty acid can be reversely oxidized to synthesize medium-chain fatty acid, and the research finds that Clostridium kluyverixx is the most widely recognized medium-chain fatty acid synthesis strain at present, and can convert acetic acid and ethanol into high-concentration caproic acid; in addition, the strain can also utilize the synthetic gas wastewater (wastewater with high ethanol/acetic acid ratio) to carry out carbon chain extension reaction, and further generate caproic acid and caprylic acid. In addition, the domestic patent CN 107142288A also discloses a method for producing acetic acid and octanoic acid by fermenting synthesis gas by mixed flora. The chentaichen kou and the like also obtain caproic acid by performing chain extension reaction on excess sludge anaerobic fermentation liquor, but the short-chain fatty acid in primary fermentation liquor is relatively simple (mainly comprising acetic acid and butyric acid), and only caproic acid is detected in products (chentaichen kou, research on producing medium-chain fatty acid by excess sludge based on anaerobic fermentation, university of Hunan, 2018). In conclusion, the existing research or patent is mostly directed to acetic acid-ethanol wastewater with relatively simple substrate or component, and the product is mainly single caproic acid; however, no report is found on the research of simultaneously producing various medium-chain fatty acids by using a mixed short-chain fatty acid solution. And the anaerobic fermentation liquid of the livestock and poultry manure contains a plurality of short-chain fatty acids, so compared with the method of adopting a single substrate and wastewater containing acetic acid or ethanol, the method of adopting the mixed fatty acid solution to carry out chain type elongation reaction to produce the medium-chain fatty acids has wider application prospect.

Disclosure of Invention

The invention aims at the technical problem and provides a method for producing medium-chain fatty acid (MCCA) by using livestock and poultry manure fermentation liquor, which comprises the following steps:

s1, carrying out heat treatment on the seeded sludge; the heat treatment is heating in water bath at 85 ℃ for 3-5 h;

s2, adding a mixed short-chain fatty acid solution into the thermally-treated inoculated sludge;

s3, adding ethanol to drive the carbon chain extension reaction of the mixed short-chain fatty acid to produce the medium-chain fatty acid, controlling the pH value in the process of the carbon chain extension reaction to be 6.5-7.0, and determining the addition amount of the ethanol based on the molar ratio of the ethanol to the short-chain fatty acid (2-5): 1.

Wherein the amount of ethanol added is 2:1 based on the molar ratio of ethanol to short chain fatty acids.

The invention has the beneficial effects that:

the invention aims at the complex short-chain fatty acid component of the livestock and poultry manure fermentation liquor, and determines a method for producing medium-chain fatty acid-n-hexanoic acid and n-heptanoic acid and n-octanoic acid which are difficult to obtain in the fermentation of general organic matters by utilizing the short-chain fatty acid component through a large amount of researches.

The method for producing the medium-chain fatty acid by using the livestock and poultry manure fermentation liquor pretreats the sludge in a water bath heating mode of 85 ℃ for 3-5 hours, reduces the metabolic activity of methanogens in the inoculated sludge, reduces the methanation effect of organic acid, and does not need to add other chemical inhibitors.

The method for producing the medium-chain fatty acid by using the livestock and poultry manure fermentation liquor controls the pH value in the fermentation process to be 6.5-7.0 so as to maintain the metabolic activity of medium-chain fatty acid synthetic flora and avoid the inhibition effect of molecular organic acid on microbial flora.

Drawings

FIG. 1 is a graph showing the distribution of medium-chain fatty acid content in the fermentation process in example 1 of the present invention when pH was controlled to different ranges;

FIG. 2 is a graph showing the production of medium-chain fatty acids at different ethanol/short-chain fatty acid ratios in example 1 of the present invention;

FIG. 3 is a graph showing the distribution of medium-chain fatty acid content during parameter validation fermentation in example 1 of the present invention.

Detailed Description

The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.