阅读说明：本技术 一种以含糖废水为原料不加电子供体产中链脂肪酸的方法 (Method for producing medium-chain fatty acid by taking sugar-containing wastewater as raw material without electron donor ) 是由 孙婧 张子莎 倪丙杰 徐秋翔 吴书林 王云 张路 于 2020-04-30 设计创作，主要内容包括：本发明涉及一种以含糖废水为原料不加电子供体产中链脂肪酸的方法,包括以下步骤：以含糖废水作为发酵底物,以酵母菌为发酵菌,在第一发酵反应器中进行第一次厌氧发酵,产生乙醇,并将发酵液输入第二发酵反应器；将污泥作为发酵接种物在第二发酵反应器中,进行第二次厌氧发酵,得到中链脂肪酸。与现有技术相比,本发明通过两步发酵的原理,耦合了乙醇的产生过程和中链脂肪酸的产生过程,其中先通过制糖废水添加酵母菌发酵产乙醇,再接种污泥产生中链脂肪酸,发酵过程简单、可操作性强,与传统的中链脂肪酸生产方式相比省去了电子供体的投加,实现了制糖废水和污泥的充分高效利用,也为实际生产过程节约了成本。(The invention relates to a method for producing medium-chain fatty acid by taking sugar-containing wastewater as a raw material without an electron donor, which comprises the following steps: taking sugar-containing wastewater as a fermentation substrate, taking saccharomycetes as zymogens, carrying out first anaerobic fermentation in a first fermentation reactor to generate ethanol, and inputting fermentation liquor into a second fermentation reactor; and performing secondary anaerobic fermentation on the sludge serving as a fermentation inoculum in a second fermentation reactor to obtain the medium-chain fatty acid. Compared with the prior art, the invention couples the production process of ethanol and the production process of medium-chain fatty acid by the principle of two-step fermentation, wherein yeast is added into the sugar-making wastewater to ferment and produce ethanol, and then sludge is inoculated to produce medium-chain fatty acid, the fermentation process is simple and strong in operability, and compared with the traditional medium-chain fatty acid production mode, the addition of an electron donor is omitted, so that the full and efficient utilization of the sugar-making wastewater and the sludge is realized, and the cost is saved for the actual production process.)

1. A method for producing medium-chain fatty acid by taking sugar-containing wastewater as a raw material without an electron donor is characterized by comprising the following steps:

taking sugar-containing wastewater as a fermentation substrate, taking saccharomycetes as zymogens, carrying out first anaerobic fermentation in a first fermentation reactor to generate ethanol, and inputting fermentation liquor into a second fermentation reactor;

and adding the sludge serving as a fermentation inoculum into a second fermentation reactor, and performing secondary anaerobic fermentation to obtain the medium-chain fatty acid.

2. The method for producing medium-chain fatty acid from sugar-containing wastewater without electron donor according to claim 1The method is characterized in that the medium-chain fatty acid is C₆～C₁₂A fatty acid.

3. The method for producing medium-chain fatty acids from sugar-containing wastewater without electron donor according to claim 1, wherein the COD of the sugar-containing wastewater is 2000-20000 mg/L.

4. The method for producing medium-chain fatty acids from sugar-containing wastewater without an electron donor as claimed in claim 1, wherein the first anaerobic fermentation and the second anaerobic fermentation are both continuous fermentation.

5. The method for producing medium-chain fatty acids from sugar-containing wastewater without electron donor as claimed in claim 4, wherein the concentration of yeast is 0.1-1.0 g/L and the pH of the fermentation broth is controlled to 5-10 during the first anaerobic fermentation.

6. The method for producing medium-chain fatty acids from sugar-containing wastewater without an electron donor according to claim 4, wherein the temperature of the fermentation liquid in the first anaerobic fermentation process is 28-40 ℃, the hydraulic retention time of the fermentation liquid is 1-5 days, and the stirring speed during fermentation is 160-180 rpm.

7. The method of claim 1, wherein the sludge is activated sludge from a municipal sewage plant.

8. The method for producing medium-chain fatty acids from sugar-containing wastewater as a raw material without an electron donor according to claim 5, wherein in the second anaerobic fermentation process, the pH of the fermentation liquid is 5-7, the temperature is 28-40 ℃, the hydraulic retention time of the fermentation liquid is 10-20 d, and the stirring speed during fermentation is 160-180 rpm.

9. The method for producing medium-chain fatty acids from sugar-containing wastewater without electron donor as claimed in claim 8, wherein the pH of the fermentation broth is controlled to 5 in both the first and second anaerobic fermentations.

10. The method for producing medium-chain fatty acids from sugar-containing wastewater without an electron donor as claimed in claim 1, wherein after the first anaerobic fermentation is completed, the fermentation liquid in the first fermentation reactor is precipitated to obtain a supernatant, and the supernatant is transferred to the second fermentation reactor.

Technical Field

The invention relates to the field of water pollution control and resource utilization, in particular to a method for producing medium-chain fatty acid by using sugar-containing wastewater as a raw material without an electron donor.

Background

Coal, oil and natural gas are the main energy supply modes in the world at present, and the fossil energy needs millions of years to be formed and belongs to non-renewable energy. At the same time, however, with the development of economy, the demand for energy is also increasing. Therefore, to alleviate the energy crisis, the development of renewable energy sources has also become a global consensus. Through the reutilization of waste biomass, biomass energy can be produced, the energy crisis is relieved to a certain extent, and the biomass energy can be used for replacing downstream products based on fossil fuels, so that the adverse effect of fossil fuel exhaustion on the development of human beings is reduced.

The sugar industry plays an important role in national economy of China and is also one of key industries for preventing and treating water pollution. COD of waste water discharged from sugar industry_CrAnd nitrogen and phosphorus are higher in concentration, the production is mainly carried out in winter, the water environment capacity is low during the production, the pollutant degradation speed is low, and therefore the influence of the discharge of the sugar industry wastewater on the regional water environment quality is larger. On the other hand, wastewater produced in the sugar industry is a potential resource, and can be reused as a raw material for anaerobic fermentation because of its high organic content and high susceptibility to microbial degradation. CN106350448A discloses a biological sewage reaction device for producing hydrogen by fermenting sugar-containing wastewater, which comprises a reactor, wherein the reactor is internally provided with a first clapboard and a second clapboard which are arranged up and downDivide into exhaust unit, reaction unit and play water unit triplex, the top that lies in into water exhaust unit on the reactor is provided with the gas vent, it is provided with the water inlet on the lateral wall of exhaust unit to lie in into water on the reactor, it is provided with the delivery port on the lateral wall of play water unit to lie in on the reactor, the bottom that lies in out water unit on the reactor is provided with the mud discharging port, it has the polyvinyl chloride filler to fill between first baffle and the second baffle, and this technical scheme adopts downflow reaction unit to handle high concentration organic waste water, and anaerobism fermentation produces hydrogen simultaneously.

By adding an electron donor (ethanol, lactic acid, etc.), short chain fatty acids generated by fermentation of an organic substrate can be converted into medium chain fatty acids (C) via a carbon chain elongation process₆-C₁₂). The medium-chain fatty acid has higher energy density and stronger hydrophobicity due to longer carbon chain, so that the medium-chain fatty acid can be separated from a fermentation system through a subsequent extraction process. Medium chain fatty acids are also high value added products that can be used not only directly as antimicrobial and food additives, but also further processed into liquid biofuels, including diesel and aviation fuels. However, despite the wide use of medium chain fatty acids, the cost of producing them is currently quite expensive. Medium chain fatty acids are usually derived from vegetable or animal oils, petroleum, and so production based on waste biomass is an economic and environmentally friendly option.

The traditional carbon chain extension process can not be separated from the adding of external electrons, common electron donors such as ethanol, lactic acid and the like have higher price, and the production cost is greatly increased in the long-term stable production process, so that the stable production means for limiting the adding of the electron donors needs to be explored.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a method for producing medium-chain fatty acid by using sugar-containing wastewater as a raw material without an electron donor. In addition, the method also has the advantages of safety, stability and strong operability.

The purpose of the invention can be realized by the following technical scheme:

the method for producing medium-chain fatty acid by taking the sugar-containing wastewater as the raw material without an electron donor comprises the following steps:

taking sugar-containing wastewater as a fermentation substrate, taking saccharomycetes as zymogens, carrying out first anaerobic fermentation in a first fermentation reactor to generate ethanol, and inputting fermentation liquor into a second fermentation reactor;

and performing secondary anaerobic fermentation on the sludge serving as a fermentation inoculum in a second fermentation reactor to obtain the medium-chain fatty acid.

Further, the medium-chain fatty acid is C₆～C₁₂A fatty acid.

Furthermore, the COD of the sugar-containing wastewater is 2000-20000 mg/L. The concentration of the waste water discharged from the sugar industry generally falls within this range.

Further, the first anaerobic fermentation and the second anaerobic fermentation are both continuous fermentation. Stable fermentation reaction conditions are obtained by continuous fermentation.

Further, in the first anaerobic fermentation process, the concentration of the yeast is 0.1-1.0 g/L, and the pH value of the fermentation liquor is controlled to be 5-10. The first fermentation step involves a wide pH range to obtain optimal ethanol production conditions over a broad range of pH.

Further preferably, the pH of the fermentation broth is controlled to 5. The highest ethanol yield was obtained under these conditions.

Furthermore, in the first anaerobic fermentation process, the temperature of the fermentation liquid is 28-40 ℃, which is a medium-temperature fermentation range and is suitable for the growth of most microorganisms. The hydraulic retention time of the fermentation liquor is 1-5 d, and sugar is fully converted into a target substance in the time. The stirring speed during fermentation is 160-180 rpm, the rotation speed less than 160rpm is defined as the too low rotation speed in the technical scheme, the sufficient contact between the microorganisms and the raw materials cannot be kept, the rotation speed exceeding 180rpm is defined as the too high rotation speed in the technical scheme, and the too high rotation speed may influence the normal physiological process of the microorganisms.

Further, the sludge is activated sludge of a municipal sewage plant. The activated sludge contains microorganisms capable of performing a carbon chain extension reaction to produce medium chain fatty acids.

Further, in the second anaerobic fermentation process, the pH value of the fermentation liquor is 5-7, the temperature is 28-40 ℃, the hydraulic retention time of the fermentation liquor is 10-20 d, and the stirring speed during fermentation is 160-180 rpm. The pH and temperature of the second fermentation process are selected based on that under the pH condition, the strains with the extended carbon chains can grow well, and the reactants can fully react due to the hydraulic retention time of 10-20 d.

Further, after the first anaerobic fermentation is completed, the fermentation liquid in the first fermentation reactor is precipitated to obtain supernatant, and the supernatant is input into the second fermentation reactor.

Compared with the prior art, the invention has the following advantages:

1) the fermentation substrate used in the invention is the sugar-containing wastewater which has wide sources and is rich in a plurality of organic matters easy to be degraded by microorganisms, belongs to waste resources with high recycling value, and fully converts the sugar-containing wastewater into medium-chain fatty acid through two reactions.

2) According to the invention, the ethanol production process and the medium-chain fatty acid production process are coupled by the principle of two-step fermentation, wherein yeast is added into the sugar-making wastewater to ferment and produce ethanol, and then sludge is inoculated to produce medium-chain fatty acid.

Drawings

FIG. 1 is a schematic view of the structure of a reactor in the two-step fermentation reaction according to the present invention.

In the figure, 1-water distribution tank, 2-pump, 3-pH probe, 4-temperature probe, 5-stirrer, 6-automatic control device, 7-waste gas collecting tank, 8-baiting valve, 9-sludge tank, 10-liquid phase sampling port and 11-gas phase sampling port.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.