CN114686535A - A method for pretreating alcoholic fermentation wastewater to improve the conversion rate of oily yeast and control the composition of oily fatty acids - Google Patents

Abstract

The invention discloses a method for pretreating alcoholic fermentation wastewater to improve the conversion rate of oleaginous yeast and regulating the composition of microbial oils and fatty acids. Detoxification conditions are controlled by different requirements of transformation efficiency and fatty acid composition, the process is simple and feasible, low cost, and can significantly reduce the toxicity of fermentation inhibitors to oil yeast. The degree of removal of fermentation inhibitors in wastewater is different, and the composition of microbial oil fatty acids produced by oil yeast fermentation is controlled to obtain products with higher added value and rich in high unsaturated fatty acids.

Description

A method for pretreating alcoholic fermentation wastewater to improve the conversion rate of oil yeast and control the composition of oil and fatty acids

Technical field:

The invention relates to a method for pretreating alcoholic fermentation wastewater, improving the conversion rate of oil yeast and regulating the composition of microbial oil and fatty acid.

Background technique:

Ethanol and butanol produced from lignocellulose are considered to be the most promising renewable fuels that can replace petroleum. The production principle is to hydrolyze the raw materials rich in lignocellulose into a cellulose hydrolyzate rich in available sugars (glucose, xylose, cellobiose, arabinose, etc.) through pretreatment and enzymatic hydrolysis, and then undergo fermentation and Alcohols are obtained by rectification process, and a large amount of waste water will be produced during the fermentation production of alcohols, and direct discharge will cause great pollution to the environment. Alcohol fermentation wastewater is rich in organic acid components, fermentation residual sugar and by-products remaining in the hydrolysis of lignocellulosic raw materials and subsequent fermentation processes. Sugars and organic acids produce microbial oils and reduce COD, so the route of converting nutrients in alcoholic fermentation wastewater into microbial oils using oleaginous yeast is economically feasible. However, in industry, the detoxification process of alcohol fermentation wastewater and the control process of fatty acid composition have always been the bottleneck restricting the development of biofuels.

The pretreatment process of lignocellulose produces by-products such as aldehydes (furfural, 5-hydroxymethylfurfural) and phenols. These by-products are difficult to be absorbed and utilized by microorganisms in the later alcohol fermentation, and will be discharged with wastewater after the fermentation. The severe conditions of the pretreatment process also produce a large amount of refractory pigment substances. Pretreatment methods such as dilute acid treatment and ammonia fiber blasting can also lead to high levels of sulfate and ammonia nitrogen in wastewater. The inhibitory effect of these fermentation inhibitors on the fermentation of oleaginous yeast is mainly manifested in the inhibition of bacterial growth, sugar metabolism process and oil accumulation. Therefore, the removal of fermentation inhibitors is of great significance for the production of microbial oils by oleaginous yeasts using alcohol waste water for fermentation. The fatty acid composition of microbial oil is close to that of vegetable oil, and its main components are mainly C16 and C18 fatty acids, such as palmitic acid, stearic acid, oleic acid and linolenic acid, etc., which can not only be used as a substitute for important oils and fats in food ( Such as cocoa butter, etc.), and can also provide various functional oils that are beneficial to human health. Overall, the lipid fatty acid composition of microbial lipids determines the usefulness of microbial lipids. Therefore, it is very important to find a simple, efficient and short-cycle method for regulating the fatty acid composition of microbial oils.

Invention content:

The object of the present invention is to provide a method for pretreating alcoholic fermentation wastewater to improve the conversion rate of oil yeast and regulating the composition of microbial oil and fatty acids, adding a detoxifier, significantly reducing the toxicity of fermentation inhibitors to oil yeast, and improving the conversion efficiency of oil yeast. At the same time, different detoxifiers can remove different degrees of fermentation inhibitors in alcoholic wastewater, control the composition of microbial oil fatty acids produced by oil yeast fermentation, and obtain products rich in high unsaturated fatty acids with higher added value.

The present invention is achieved through the following technical solutions:

A method for pretreating alcoholic fermentation wastewater to improve the conversion rate of oil yeast and regulating the composition of microbial oil and fatty acid, the method comprises the following steps:

a. After filtering out the solids in the alcoholic fermentation wastewater, add a detoxifying agent in a proportion of 0.5wt% to 5wt%, and after stirring and reacting for a period of time, filter or precipitate to remove the detoxifying agent, so that the furfural content in the filtrate is ≤5g/L, 5-Hydroxymethylfurfural content≤5g/L, phenolic content≤6g/L, ammonia nitrogen content≤3g/L, light transmittance≤70% to obtain the detoxified filtrate; the detoxification agent is activated carbon, A kind of attapulgite, zeolite, polar or non-polar macroporous adsorption resin;

b. Take the detoxified filtrate and connect it to the oil yeast seed liquid for aerobic fermentation.

The stirring includes one of paddle stirring, screw propelling stirring, anchor stirring, frame stirring, etc. The stirring speed is 50-300 rpm/min, and the time is 0.5-2 h.

The oleaginous yeast is one or more of Rhodotorula glutinis, Trichosporon cutaneum, Rhodosporidium toruloides, Lipomyces starkeyi, Cryptococcus albidus, Trichosporon dermatis, Trichosporn coremiiforme, and Yarrowia lipolytica.

The invention uses different detoxifiers to remove different degrees of fermentation inhibitors in alcoholic wastewater, and at the same time improves the conversion efficiency of oil yeast, the composition of microbial oil fatty acid produced by fermentation of oil yeast is regulated.

The beneficial effects of the present invention are as follows: the present invention aims at the complex composition of the alcoholic fermentation wastewater after fermentation and high-temperature distillation, and the fermentation inhibitors are abundant. The detoxification conditions are controlled according to the different requirements of the conversion efficiency and fatty acid composition of alcohol wastewater. The process is simple and feasible, the cost is low, and the toxicity of fermentation inhibitors to oil yeast can be significantly reduced. The degree of removal of fermentation inhibitors in alcoholic wastewater is different, and the composition of microbial oil fatty acids produced by the fermentation of oil yeast is controlled to obtain products with higher added value and rich in high unsaturated fatty acids.

Detailed ways:

The following is a further description of the present invention, rather than a limitation of the present invention.

Example 1:

Activated carbon was used to detoxify the ethanol fermentation wastewater, and Trichosporoncutaneum was used for fermentation after the treatment.

Insert Trichosporon cutaneum from the test tube into 50 mL of activation medium, and at 20° C., activate and cultivate for 24 hours to obtain Trichosporon cutaneum seed liquid. The activated medium is: glucose 20g/L, peptone 10g/L, yeast powder 10g/L L, the balance is water.

In the control group, activated carbon was not used in the medium of ethanol fermentation wastewater for detoxification, and the seed liquid was directly connected to the medium for fermentation.

Activated carbon was added to the ethanol fermentation wastewater in the proportions of 0.5wt% and 5wt% respectively, and the paddle stirring method was adopted. The stirring condition was 50rpm/min for 0.5h. After the stirring was completed, the activated carbon was removed by filtration, and the filtrate was taken to determine the aldehyde. (furfural, 5-hydroxymethylfurfural), phenols, ammonia nitrogen content, and measure the light transmittance; after adjusting the pH, the oil yeast seed liquid was connected to carry out aerobic fermentation, and the yeast cells in the ethanol fermentation wastewater were collected by centrifugation. Fermentation substrates are subsequently processed according to discharge requirements. Table 1 shows the detoxification of each component of fermentation inhibitor with different activated carbon additions. The regulation of different amounts of activated carbon on the fatty acid content of microbial oils is shown in Table 2. The regulation of different amounts of activated carbon on the transformation efficiency of oil yeast is shown in Table 3.

Table 1

Component content Before detoxification 0.5% after detoxification 5% after detoxification Furfural (g/L) 4.754 1.253 0.724 5-Hydroxymethylfurfural (g/L) 2.694 1.402 0.951 Total phenols (g/L) 5.621 4.310 2.518 Transmittance(%) 31 32 75 Ammonia nitrogen (g/L) 2.748 0.951 0.810

Table 2

table 3

Component content Before detoxification 0.5% after detoxification 5% after detoxification Oil content (%) 12.8 14.2 15.7 Oil yield (g/L) 0.54 0.75 0.83

Example 2:

The ethanol fermentation wastewater was detoxified by attapulgite, and then fermented by Rhodosporidium toruloides after the treatment.

Put Rhodosporidium toruloides from the test tube into 50 mL of activation medium, 20 ° C, activate and cultivate for 24 hours, to obtain Rhodosporidium toruloides seed liquid, the activation medium is: glucose 20g/L, peptone 10g/L, yeast powder 10g/L L, the balance is water.

In the control group, the attapulgite was not used for detoxification in the ethanol fermentation wastewater medium, and the seed liquor was directly fermented.

Attapulgite was added to the ethanol fermentation wastewater in a proportion of 2wt%, and the attapulgite was respectively stirred by anchor stirring for 0.5 and 2 hours, and the rotation speed was 200 rpm/min. (furfural, 5-hydroxymethylfurfural), phenols, ammonia nitrogen content, and measure the light transmittance; after adjusting the pH, the oil yeast seed liquid was connected to carry out aerobic fermentation, and the yeast cells in the ethanol fermentation wastewater were collected by centrifugation. Fermentation substrates are subsequently processed according to discharge requirements.

Table 4 shows the detoxification of each component of the fermentation inhibitor at different stirring times. Table 5 shows the regulation of different stirring time on the fatty acid content of microbial oil. Table 6 shows the regulation of the transformation efficiency of oil yeast by different stirring times.

Table 4

Component content Before detoxification 0.5h 2h Furfural (g/L) 2.654 1.105 0.721 5-Hydroxymethylfurfural (g/L) 2.987 1.240 0.864 Total phenols (g/L) 5.745 2.314 1.055 Transmittance(%) twenty four 46 76 Ammonia nitrogen (g/L) 2.023 0.954 0.745

table 5

Component content Before detoxification 0.5h 2h C16:0 49.1 48.4 42.8 C18:0 21.4 21.5 17.5 C18:1 16.4 18.4 24.1 C18:2 8.1 10.5 10.9 other 5.0 1.2 4.7

Table 6

Example 3:

The butanol fermentation wastewater was detoxified by polar macroporous adsorption resin, and Rhodotorula glutinis and Lipomyces starkeyi were used for mixed bacterial fermentation after the treatment.

The Rhodosporidium toruloides and Lipomyces starkeyi were respectively inserted into 50 mL of activated medium from the test tube, and activated for 24 hours at 20°C to obtain seed liquid. The activated medium was: glucose 20g/L, peptone 10g/L, yeast powder 10g/L, the balance is water.

In the control group, the butanol fermentation wastewater medium did not use polar macroporous adsorption resin for detoxification, and the seed liquid was directly connected to the medium for fermentation.

The polar macroporous adsorption resin was added to the butanol fermentation wastewater in a proportion of 2 wt%, and stirred for 2 hours by means of screw propeller stirring, and the sum of the rotational speed was 100 rpm/min. After the stirring was completed, the polar macroporous adsorption was removed by precipitation. Resin, take the filtrate to measure the content of aldehydes (furfural, 5-hydroxymethyl furfural), phenols, ammonia nitrogen, and measure the light transmittance; adjust the pH and then insert the oil yeast seed liquid for aerobic fermentation, and collect butanol fermentation by centrifugation Yeast cells in wastewater, and fermentation substrates are subject to subsequent treatment according to discharge requirements

Experimental results: (1) In terms of mass fraction, in the filtrate without polar macroporous adsorption resin for detoxification, the furfural content was 1.357g/L, the 5-hydroxymethylfurfural content was 2.504g/L, and the total phenolic The content is 4.658g/L, and the ammonia nitrogen content is 1.023g/L. In the filtrate detoxified by polar macroporous adsorption resin, the furfural content was 0.854g/L, the 5-hydroxymethylfurfural content was 0.574g/L, the total phenol content was 1.214g/L, and the ammonia nitrogen content was 0.548g /L. (2) In terms of mass fraction, in the fermentation medium without the use of polar macroporous adsorption resin for detoxification, the oil content of the microbial oil produced by the mixed fermentation of Rhodotorula glutinis and Lipomycesstarkeyi was 8.1%, and the oil yield was 0.89g /L, the fatty acid composition was: palmitic acid 38.1%, stearic acid 31.8%, oleic acid 10.4%, linoleic acid 12.1%, and others 7.6%. In the fermentation medium after detoxification with polar macroporous adsorption resin, the oil content of the produced microbial oil was 12.5%, the oil yield was 1.02 g/L, and the fatty acid composition was: palmitic acid 31.9%, stearic acid 32.6% %, oleic acid 14.7%, linoleic acid 16.8%, other 4%.

Example 4:

The butanol fermentation wastewater was detoxified with non-polar macroporous adsorption resin, and then fermented with Trichosporn coremiiforme after the treatment.

The Trichosporn coremiiforme was inserted into 50 mL of activation medium from the test tube, and activated at 20° C. for 24 hours to obtain Trichosporn coremiiforme seed liquid. The activated medium was: glucose 20g/L, peptone 10g/L, yeast powder 10g/L L, the balance is water.

In the control group, non-polar macroporous adsorption resin was not used in the medium of butanol fermentation wastewater for detoxification, and the seed liquid was directly connected to the medium for fermentation.

The non-polar macroporous adsorption resin was added to the butanol fermentation wastewater in a proportion of 2wt%, and the stirring method was adopted. The stirring time was 1h, and the rotating speed was 50 and 300 rpm/min respectively. After stirring, the non-polar macroporous adsorption resin was removed by filtering. macroporous adsorption resin, the filtrate was taken to measure the content of aldehydes (furfural, 5-hydroxymethylfurfural), phenols and ammonia nitrogen, and the light transmittance was measured; after adjusting the pH, it was connected to the oil yeast seed liquid for aerobic fermentation, and centrifugation The yeast cells in the ethanol fermentation wastewater are collected, and the fermentation substrate is subjected to subsequent treatment according to the discharge requirements. Table 7 shows the effect of detoxification on the components of fermentation inhibitors at different speeds, Table 8 shows the effect of detoxification on the fatty acid content of microbial oils at different speeds, and Table 9 shows the addition amount of different non-polar macroporous adsorption resins Regulation of the transformation efficiency of oleaginous yeast.

Table 7

Component content Before detoxification 50rpm/min 300rpm/min Furfural (g/L) 2.357 1.345 1.025 5-Hydroxymethylfurfural (g/L) 2.804 1.420 1.140 Total phenols (g/L) 5.957 3.254 2.352 Transmittance(%) 20 25 57 Ammonia nitrogen (g/L) 2.954 0.698 0.542

Table 8

Component content Before detoxification 50rpm/min 300rpm/min C16:0 54.2 48.5 47.1 C18:0 21.7 15.3 14.4 C18:1 12.1 25.1 29.9 C18:2 4.5 6.7 7.0 other 7.5 4.4 1.6

Table 9

Component content Before detoxification 50rpm/min 300rpm/min Oil content (%) 13.7 14.2 17.2 Oil yield (g/L) 0.68 0.78 0.81

Claims (4)

1. A method for pretreating alcohol fermentation wastewater to improve the conversion rate of grease yeast and regulate and control the composition of microbial grease fatty acid is characterized by comprising the following steps:

1) filtering solid matters in the alcohol fermentation wastewater, adding a detoxifying agent according to the proportion of 0.5-5 wt%, stirring for reaction for a period of time, and filtering or precipitating to remove the detoxifying agent so that the furfural content in the filtrate is less than or equal to 5g/L, the 5-hydroxymethylfurfural content is less than or equal to 5g/L, the phenol content is less than or equal to 6g/L, the ammonia nitrogen content is less than or equal to 3g/L, and the light transmittance is less than or equal to 70% to obtain detoxified filtrate; the detoxifying agent is one of activated carbon, attapulgite, zeolite and polar or non-polar macroporous adsorption resin;

2) inoculating the detoxicated filtrate into the oil yeast seed liquid for aerobic fermentation.

2. The method for improving the conversion rate of grease yeast and regulating and controlling the composition of microbial grease fatty acid by pretreating alcohol fermentation wastewater according to claim 1, wherein the stirring comprises one of paddle stirring, screw propulsion stirring, anchor stirring and frame stirring, the stirring speed is 50-300 rpm/min, and the stirring time is 0.5-2 hours.

3. The method for pretreating alcohol fermentation wastewater to improve the conversion rate of lipid yeast and control the fatty acid composition of microbial oil according to claim 1, wherein the lipid yeast is one or more of Rhodotorula glutinis, Trichosporon cutaneum, Rhodosporidium toruloides, Lipomyces starkeyi, Cryptococcus albicus, Trichosporon dematis, Trichosporon coremiforme, and Yarrowia lipolytica.

4. The method for improving the conversion rate of lipid yeast and regulating the composition of microbial lipid fatty acid by pretreating alcohol fermentation wastewater according to claim 1, wherein the composition of microbial lipid fatty acid produced by fermentation of lipid yeast is regulated while the conversion rate of lipid yeast is improved by removing fermentation inhibitors from alcohol wastewater to different degrees through different detoxifiers.