CN101220379A - Method for producing ethyl alcohol by using sorgo stalk - Google Patents

Abstract

The invention discloses an ethanol production method by utilizing sweet sorghum stalks, which pertains to the field of plant fuel. The invention includes the following steps that: the juice and the residue of the sweet sorghum stalks are separated, then the sweet sorghum residue is treated with diluted acid explosion pretreatment, fermentable sugar is obtained by the enzymolysis of a cellulase , then the sweet sorghum juice and the sorghum residue are processed to obtain the fermented sugar liquid, concentration and regulation of the fermented sugar liquid are carried out, and finally the ethanol is prepared by using the brewing yeast for fermentation. The method of the invention can make full use of the sweet sorghum stalks and has the advantages of short fermentation time, high enzymolysis efficiency of the cellulose, high ethanol yield, etc.

Description

Method for producing ethanol from sweet sorghum stalks

technical field

The invention belongs to a biofuel production method, in particular to a method for producing ethanol by using sweet sorghum stalks.

Background technique

Excessive exploitation and use of oil, natural gas, and coal have caused the world to face serious energy and environmental crises. Finding alternative, sustainable, environmentally friendly green energy has become the focus of the world's energy strategy. Biofuel ethanol is a feasible alternative. At present, China mainly produces fuel ethanol with aged grains as raw materials. , the CO ₂ release of grain ethanol has not been reduced, and the purpose of environmental protection cannot be achieved. At the same time, the use of grain to produce fuel ethanol not only costs high, but also causes waste of grain. Therefore, it is necessary to find new plant raw materials for the production of biofuels. Sweet sorghum stalks are rich in sugar and fiber, and are an ideal raw material for the production of fuel ethanol.

Compared with other energy crops that can produce alcohol, sweet sorghum has incomparable advantages: first, in the biomass energy system, sweet sorghum is the first competitor, and can harvest 2250-7500 kilograms of seeds per hectare, The stalks are rich in sugar, and the yield is extremely high. Generally, the yield of fresh stalks per hectare is about 75 tons. Second, sweet sorghum is a high-energy crop. During the vigorous growth period, the carbohydrates synthesized by sweet sorghum per hectare can produce 48 liters of alcohol per day, while that of corn is only 15 liters, that of wheat is 3 liters, and that of sorghum for grain is only 9 liters. Third, sweet sorghum not only has high yield, but also has wide adaptability, drought resistance, waterlogging tolerance, and salt-alkali tolerance. It is the "camel" among crops. Sweet sorghum can be cultivated in various types of soil with a pH value of 5-8.5. On saline-alkali soil with a salt content of 0.36%-0.53%, sweet sorghum can grow normally, and the output can reach 4-5.5 tons. Due to the limited area of arable land in our country, saline-alkali land, especially the saline-alkaline soil of coastal tidal flats, is the most ideal area for the development of fuel ethanol industry, and sweet sorghum is one of the most suitable raw material crops for the production of fuel ethanol.

At present, the production of fuel ethanol from sweet sorghum stalks is mainly carried out by fermenting the sap of sweet sorghum stalks or grains plus juice, such as the patent application "Method for Producing Ethanol from Sweet Sorghum Stalk Juice" (Application No.: 200510076833.7), "Using Sweet sorghum stalk production ethanol liquid fermentation technology" (application number: 200410035604.6), "sweet sorghum stalk production ethanol process method" (application number: 02151719.3), "a kind of fuel ethanol and its production process" (application number No.: 2007100022972.4), "Technology for Producing Ethanol Using Sweet Sorghum Stalk or Sweet Sorghum Dry Straw as Raw Material" (Application No.: 200610134397.9), etc., mainly utilize sweet sorghum stalk juice to produce ethanol, "Use Sweet Sorghum Straw and its The method for producing ethanol from grains" (application number: 200710057584.6), "method for producing ethanol with sweet sorghum stalks" (application number: 200710010720.6), etc. utilize sweet sorghum stalk juice and grains to produce ethanol, and these inventions use the stalk Juice fermentation only utilizes part of the soluble sugar in the sweet sorghum stalk, and discards or burns the structural sugar in the form of cellulose and hemicellulose that is almost equal to the soluble sugar in the sweet sorghum dregs, which not only causes a lot of waste, Raw material utilization rate is low, and has caused air and environmental pollution. With the improvement of cellulose pretreatment technology, the US Biomass Processing Application Innovation Consortium (CAFI) has achieved great results in acid pretreatment and ammonia blast pretreatment; international advanced enzyme preparation companies, such as Novozymes and Genen The reduction of the price of cellulase will make it possible to make full use of non-structural and structural sugars in sweet sorghum stalks to produce fuel ethanol, which will greatly increase the utilization rate of raw materials and the yield of ethanol.

Contents of the invention

The object of the present invention is to provide a method for producing ethanol by using sweet sorghum stalks, which can make full use of non-structural sugars and structural sugars in sweet sorghum stalks, has high raw material utilization rate and high ethanol yield.

In order to achieve the above object, the technical scheme adopted in the present invention is:

The method for producing ethanol from sweet sorghum stalks comprises the steps of:

(1) Squeezing mature sweet sorghum stalks to obtain stalk juice and sweet sorghum slag;

(2) Carry out dilute acid blasting pretreatment to sweet sorghum slag;

(3) Enzymolysis and saccharification of sweet sorghum residue with cellulase;

(4) mixing the sugar solution and adjusting the concentration of the sugar juice;

(5) Yeast activation;

(6) fermentation to obtain ethanol.

The pressing described in step (1) of the method for producing ethanol refers to crushing and cutting the mature sweet sorghum stalks into filamentous segments of 10 mm to 25 mm, then pressing, and then adding 10 to 20% Squeeze the fresh water twice to obtain stalk juice and sweet sorghum slag; then cook the obtained stalk juice at 85-100°C for 30-45 minutes, then centrifuge, filter, and remove sediment to obtain clarified stalk juice.

The dilute acid blasting pretreatment of the sweet sorghum slag described in step (2) of the above method for producing ethanol refers to air-drying the sweet sorghum slag obtained above or drying at 30-45°C, and then drying the sweet sorghum slag at 0.1- Soak in 0.5% H ₂ SO ₄ solution for 8-12 hours, then place it in a steam explosion tank, increase the pressure, keep it under 1.3-1.9MPa pressure for 6-10 minutes, release the pressure instantly, and collect the sweet sorghum slag obtained after steam explosion Wash the sweet sorghum slag after the acid blasting treatment with water to obtain the pretreated slurry and solid reclaimed product, add Ca(OH) ₂ to the obtained slurry to adjust the pH value to 9.5-10.5, stir for 1-1.5h, and precipitate and filter to obtain Clarified pretreatment slurry.

Enzymatic hydrolysis and saccharification of sweet sorghum slag with cellulase as described in step (3) of the above method for producing ethanol refers to adding water to immerse the above-mentioned obtained solid recovery, adjusting the pH value to 4.8-5.5, adding fiber according to the dry weight of sweet sorghum slag Sulfase 15-30 FPU/g, β-glucosidase 20-30 CBU/g, enzymolysis at 45-50°C for 72-108 hours, stirring once every 5-8 hours during this period, filtering to obtain enzymolysis sugar solution.

The adjustment of sugar juice concentration described in step (4) of the method for producing ethanol above refers to mixing the above-mentioned obtained stalk juice, pretreated slurry and enzymatic sugar solution, and then cooking and concentrating the mixed sugar solution to obtain a sugar juice concentration of 16-24% mixed sugar solution.

The yeast activation described in step (5) of the method for producing ethanol above refers to preparing yeast seed liquid according to the usual method, that is, inoculating the yeast strains preserved on a slope at 4°C into the yeast activation medium, and inoculating them at 28-32°C, 100 Cultivate in a constant temperature shaker at ~120rpm for 16~20h; then transfer to the seed medium according to the inoculum amount of 5%, and cultivate in a constant temperature shaker at 28~32°C and 100~120rpm for 18~24h; Expanded cultivation is enough; the composition and weight percentage of the activated medium are: 1.5-2% glucose, 1.5-2% peptone, 0.8-1% yeast extract, 0.15-0.2% KH ₂ PO ₄ , 0.05-0.1% MgSO ₄ , pH value 5.0; wherein the composition and weight percentage of the seed medium are: 1.5-2% glucose, 1.5-2% peptone, 0.8-1% yeast extract.

The fermentation described in step (6) of the method for producing ethanol refers to adding 0.1 to 0.3% urea, 0.15 to 0.25% MgSO ₄ ·7H ₂ O and 0.25 to 0.5% CaCl ₂ to the mixed sugar solution obtained above according to the weight percentage 2H ₂ O, then sterilize at 100-120°C for 10-15min, then insert the Saccharomyces cerevisiae seed liquid according to the juice volume ratio of 5-10%, seal and ferment at 32-35°C for 32-48 hours; then collect by distillation Ethanol, get ethanol.

The pressing described in the above-mentioned method step (1) can be carried out by a pressing machine.

The cellulase described in above-mentioned method step (4) refers to high temperature resistant cellulase, β-glucosidase or hydroxymethyl cellulase etc.; Described cellulase can be purchased from the market, as from Purchased by Hunan Youtel Biochemical Co., Ltd., Genencor Corporation, Sigma Corporation and other companies.

The Saccharomyces cerevisiae described in the above step (6) can be purchased from the market, and can also be purchased from the General Microbiology Center of China Microbiological Culture Collection Management Committee, such as alcohol-resistant yeast (Saccharomycescerevisiae 2.119).

The effect of the urea described in the above method step (6) is as a nitrogen source.

The MgSO ₄ .7H ₂ O and 0.5% CaCl ₂ .2H ₂ O described in step (6) of the above method are used as nutrient salts.

The fermentation time described in the above method step (6) can be controlled according to the weight loss caused by discharging _CO in the fermentation process.

Parts not specifically indicated in the above methods should be understood as commonly used methods or equipment.

Advantages of the present invention: (1) the sweet sorghum stalk utilization rate of the present invention is high, and both the structural sugar and the non-structural sugar in the stalk can be fully utilized; (2) the ethanol yield of the present invention is high, due to utilizing the juice and cellulose, so its ethanol yield can reach about 7.3 kilograms of ethanol per 100 kilograms of straw; (3) the saccharification efficiency of the cellulase of the present invention is high, and due to the use of dilute acid blasting treatment technology, hemicellulose, woody Separation of cellulose and cellulose structure, increasing the interstitial interval of sweet sorghum dregs structure, thus improving the saccharification efficiency of cellulase, hydrolyzing the structural sugars existing in cellulose and hemicellulose in sweet sorghum dregs to the greatest extent, and improving the conversion rate of structural sugars Can reach more than 85%; (4) the present invention adopts alcohol-resistant alcoholic yeast, can carry out high-density fermentation, has shortened fermentation time, has improved fermentation efficiency, also can save a large amount of energy, improves equipment utilization rate and production efficiency; (5) ) The present invention fundamentally changes the present situation of producing ethanol with grain as raw material.

Description of drawings

Fig. 1 is process flow chart of the present invention.

Detailed ways

Example 1

The production of ethanol using sweet sorghum stalks comprises the following steps:

(1) Juicing of sweet sorghum stalks 100 kg of sweet sorghum stalks with a water content of 72.8%, a sugar content of 13.9%, and a crude fiber content of 9.6% are crushed and cut into filamentous segments of 10mm to 25mm, and squeezed with a press machine. Then adding water to the obtained sweet sorghum dregs for secondary pressing to obtain sweet sorghum juice and silky sweet sorghum dregs with extremely low residual sugar content;

(2) Cooking sweet sorghum stalk juice at 100° C. for 30 minutes, centrifuging and filtering, removing sediment to obtain clarified sweet sorghum juice.

(3) Dilute acid blasting pretreatment of sweet sorghum slag Air-dried sweet sorghum slag naturally, soaked in 0.1% H ₂ SO ₄ solution for 12 hours, put in steam explosion tank closing device; kept at 1.5MPa pressure for 6 minutes, and released the pressure instantly, Collect steam explosion raw materials; wash the sweet sorghum slag treated by acid explosion with water to obtain pretreatment slurry and solid recovery, _add Ca(OH) to the pretreatment slurry to adjust the pH value to 10.5, stir for 1h, precipitate and filter, discard the precipitate, The filtrate was neutralized to 5.0 with H ₂ SO ₄ to obtain a clear pretreatment slurry;

(4) Enzymatic hydrolysis and saccharification of sweet sorghum slag Add water to immerse the solid recovery after sweet sorghum slag pretreatment, adjust the pH value to 5.5 with Ca(OH) ₂ , add cellulase according to the dry weight of sweet sorghum slag (Hunan Youtel Biochemical Co., Ltd. Produced by the company) 30FPU/g, β-glucosidase (Novozym 188, produced by Novozymes) 30CBU/g, enzymatically hydrolyze at 50°C for 108h, stir once every 6h, filter to obtain enzymolyzed sugar solution.

(5) Yeast culture Inoculate 20 mL of yeast seed activation medium with three rings of alcohol-resistant yeast (Saccharomycescerevisiae 2.119, obtained from the General Microbiology Center of China Microorganism Culture Collection Management Committee) preserved on a slope at 4°C, and inoculate at 32°C, 120rpm Cultivate in a constant temperature shaking table for 20 hours; then transfer 5% of the inoculum amount into 100 ml seed medium, and cultivate in a constant temperature shaking table at 32° C. and 120 rpm for 20 hours; expand the culture sequentially to obtain yeast culture solution.

(6) Adjusting the concentration of sugar juice Mix the sweet sorghum juice obtained in step (2), the pretreated slurry obtained in step (3) and the enzymatic sugar solution obtained in step (4) to obtain a mixed sugar solution, and cook and concentrate the mixed sugar solution, It is the mixed sugar liquid of 20% that the sugar juice concentration is obtained.

(7) Fermentation Add 0.3% urea, 0.25% MgSO ₄ 7H ₂ O and 0.5% CaCl ₂ 2H ₂ O to the mixed sugar solution in step (6), sterilize at 121°C for 15 minutes, and use 10% juice Add the alcohol-resistant Saccharomyces cerevisiae activation solution of step (5) into the mixed sugar solution, then seal and ferment at 32°C for 32 hours, the alcohol concentration in the fermentation solution reaches 8.3% (w/v), collect ethanol by distillation, and obtain 7.56Kg of ethanol .

Example 2

The production of ethanol using sweet sorghum stalks comprises the following steps:

(1) Juicing of sweet sorghum stalks 100Kg of sweet sorghum stalks with a water content of 72.8%, a sugar content of 13.9%, and a crude fiber content of 9.6% are crushed and cut into filamentous segments of 10mm to 25mm, squeezed with a press, and then Adding water to the obtained sweet sorghum dregs and performing secondary pressing to obtain sweet sorghum juice and silky sweet sorghum dregs with very low residual sugar content.

(2) Cooking the sweet sorghum stalk juice obtained in step (1) at 100° C. for 30 minutes, centrifuging and filtering, and removing sediment to obtain clarified sweet sorghum juice.

(3) Dilute acid blasting pretreatment of sweet sorghum slag Air-dry the sweet sorghum slag obtained in step (1), soak in 0.5% H ₂ SO ₄ solution for 8 hours, put it into a steam explosion tank, and close the device; Keep the pressure under MPa for 6 minutes, release the pressure instantly, and collect steam explosion raw materials; wash the sweet sorghum slag treated by acid explosion with water to obtain pretreated slurry and solid recovery, add Ca(OH) ₂ to the slurry to adjust the pH value to 10.5, and stir for 1 hour , filtered the precipitate, discarded the precipitate, and neutralized the filtrate to 5.0 with H ₂ SO ₄ to obtain a clear pretreatment slurry.

(4) Enzymatic hydrolysis and saccharification of sweet sorghum residue. Add water to immerse the solid recovery after sweet sorghum slag pretreatment, Ca(OH) ₂ adjust the pH value to 5.0, add cellulase (Celluclast 1.5L, produced by Novozymes) 15FPU/g according to the dry weight of sweet sorghum slag, β -Glucosidase (Novozym 188, produced by Novozymes) 30CBU/g, enzymolysis at 50°C for 72h, stirring once every 6h. Obtain enzymatic sugar solution.

(5) Yeast activation Inoculate 20ml yeast seed activation medium with alcohol-resistant yeast (Saccharomycescerevisiae 2.119, obtained from the China Common Microorganism Culture Collection and Management Center) preserved on a slope at 4°C, and culture it in a constant temperature shaker at 32°C and 120rpm 20h. Then transfer 5% of the inoculum into 100 ml of seed culture medium, and cultivate for 18 hours at 32° C. and 120 rpm in a constant temperature shaker. Sequentially expand the cultivation.

(6) Adjusting the concentration of sugar juice Mix the sweet sorghum juice obtained in step (2), the pretreated slurry obtained in step (3) and the enzymatic sugar solution obtained in step (4) to obtain a mixed sugar solution, and cook and concentrate the mixed sugar solution , It is the mixed sugar liquid of 16% that the sugar juice concentration is obtained.

(7) Fermentation Add 0.3% urea, 0.25% MgSO ₄ 7H ₂ O, 0.5% CaCl ₂ 2H ₂ O to the mixed sugar solution obtained in step (6), sterilize at 121°C for 15 minutes, and then activate Saccharomyces cerevisiae Add 10% of the juice to the mixed sugar liquid, and seal and ferment at 35°C for 32 hours. The alcohol concentration in the fermentation liquid is 6.6% (w/v), and the ethanol is collected by distillation to obtain 7.28Kg of ethanol.

Claims (8)

1. utilize sweet sorghum stalk to produce the alcoholic acid method, comprise the steps:

(1) sophisticated sweet sorghum stalk is squeezed, get stalk juice and sweet sorghum slag;

(2) the sweet sorghum slag is carried out diluted acid explosion pre-treatment;

(3) with cellulase with sweet sorghum slag enzymatic saccharification;

(4) mixed sugar liquid and regulate syrup concentration;

(5) activated yeast;

(6) fermentation gets ethanol.

2. according to the described production alcoholic acid of claim 1 method, it is characterized in that the squeezing described in its step (1) is meant the thread segment that sophisticated sweet sorghum stalk pulverizing is cut into 10mm～25mm, squeeze then, in gained sweet sorghum slag, add 10～20% water again and carry out twice pressing, stalk juice and sweet sorghum slag; Then with the gained stalk juice at 85～100 ℃ of boiling 30～45min, centrifugal, filter, go the precipitation, clarifying stalk juice.

3. according to claim 1 or 2 described production alcoholic acid methods, it is characterized in that described in its step (2) to the sweet sorghum slag carry out diluted acid explosion pre-treatment be meant above-mentioned gained sweet sorghum slag is air-dry or 30～45 ℃ of down oven dry, then with the sweet sorghum slag at 0.1～0.5%H ₂SO ₄Soaked in the solution 8～12 hours, and placed the steam explosion jar again, boost, under 1.3～1.9MPa pressure, keep 6～10min, moment pressure release, the sweet sorghum slag of the quick-fried back of collection vapour gained; Wash the sweet sorghum slag after sour explosion treatment with water, get pre-treatment slurries and solid regenerant, in the gained slurries, add Ca (OH) ₂Regulate pH value to 9.5～10.5, stir 1～1.5h, sedimentation and filtration gets clarifying pre-treatment slurries.

4. according to the described production alcoholic acid of claim 3 method, it is characterized in that sweet sorghum slag enzymatic saccharification is meant with cellulase described in its step (3) adds water to submerge gained solid regenerant in the claim 3, regulating the pH value is 4.8～5.5, add cellulase 15～30FPU/g by sweet sorghum slag dry weight, β-glucose glycoside enzyme 20～30CBU/g, in 45～50 ℃ of enzymolysis 72～108h, during stir once every 5～8h, filter the enzymolysis liquid glucose.

5. according to the described production alcoholic acid of claim 4 method, it is characterized in that the adjusting syrup concentration described in its step (4) is meant that the enzymolysis liquid glucose with gained in gained pre-treatment slurries and the claim 4 in the stalk juice of gained in the claim 2, the claim 3 mixes, get mixed sugar liquid, then mixed sugar liquid is carried out boiling and concentrates, syrup concentration is 16～24% mixed sugar liquid.

6. according to the described production alcoholic acid of claim 5 method, it is characterized in that the activated yeast described in its step (5) is meant according to usual method prepares yeast seed liquid, the yeast strain that is about to 4 ℃ of slant preservations is inoculated in the activated yeast substratum, cultivates 16～20h in the constant temperature shaking table under 28～32 ℃, 100～120rpm condition; And then transfer in the seed culture medium by 5% inoculum size, under 28～32 ℃, 100～120rpm condition, cultivate 18～24h in the constant temperature shaking table; Enlarged culturing gets final product successively; The moiety of wherein said activation medium and weight percent thereof are: 1.5～2% glucose, 1.5～2% peptones, 0.8～1% yeast extractive substance, 0.15～0.2%KH ₂PO ₄, 0.05～0.1%MgSO ₄, pH value 5.0; The moiety of wherein said seed culture medium and weight percent thereof are: 1.5～2% glucose, 1.5～2% peptones, 0.8～1% yeast extractive substance.

7. according to the described production alcoholic acid of claim 6 method, it is characterized in that the fermentation described in its step (6) is meant in the mixed sugar liquid according to weight percent gained in claim 5 and add 0.1～0.3% urea, 0.15～0.25%MgSO ₄7H ₂O and 0.25～0.5%CaCl ₂2H ₂O then at 100～120 ℃ of following sterilization 10～15min, pressed the access yeast saccharomyces cerevisiae seed liquor of juice volume ratio 5～10% again, in 32～35 ℃ of sealing and fermenting 32～48 hours; Distillation is collected then, gets ethanol.

8. according to the described production alcoholic acid of claim 6 method, it is characterized in that described yeast is ethanol-tolerant yeast Saccharomyces cerevisiae 2.119.