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CN-122012649-A - Method for coupling in-situ enzymatic hydrolysis of agricultural and forestry waste through low-concentration auxiliary agent assisted low-organic acid pretreatment

CN122012649ACN 122012649 ACN122012649 ACN 122012649ACN-122012649-A

Abstract

The invention discloses a method for coupling in-situ enzymatic hydrolysis of agricultural and forestry waste by low-concentration auxiliary agent assisted low-organic acid pretreatment. The method comprises the steps of taking crushed agricultural and forestry waste as a raw material, adding an aqueous solution containing a low-concentration auxiliary agent and an organic acid into the raw material, performing pretreatment at 140-185 ℃ and 0.5-4.0 h, cooling to 45-55 ℃ after the reaction is finished, adding 5-25 mg/g of raw material cellulase, hydrolyzing 72-h at 50 ℃, performing solid-liquid separation after the enzyme hydrolysis is finished to obtain solid residues and enzyme hydrolysate, and performing oil-producing fermentation after the pH value of the enzyme hydrolysate is regulated. The invention avoids pollution or fermentation inhibition caused by alkali, solvent or inorganic acid by auxiliary agent auxiliary organic acid pretreatment, and simultaneously improves enzyme hydrolysis efficiency to obtain fermentable sugar with higher concentration.

Inventors

  • CHEN XINDE
  • XIONG LIAN
  • LI HAILONG
  • ZHANG HAIRONG

Assignees

  • 中国科学院广州能源研究所

Dates

Publication Date
20260512
Application Date
20260214

Claims (10)

  1. 1. A coupling in-situ enzyme hydrolysis method for low-concentration auxiliary agent-assisted low-organic acid pretreatment of agricultural and forestry waste is characterized by comprising the steps of taking crushed agricultural and forestry waste as a raw material, adding an aqueous solution containing the low-concentration auxiliary agent and organic acid into the raw material, wherein the auxiliary agent is selected from more than one of propylene glycol, glycerol, tween, ethylene glycol and polyethylene glycol, the mass fraction of the auxiliary agent in the aqueous solution containing the auxiliary agent and the organic acid is 0-1.5%, the mass fraction of the organic acid in the aqueous solution containing the auxiliary agent and the organic acid is 0.5% -2.0%, the aqueous solution containing the auxiliary agent and the organic acid is reacted at 140-185 ℃ for pretreatment at 0.5-4.0 h, cooling to 45-55 ℃ after the reaction, adding 5-25 mg/g of raw material cellulase, hydrolyzing at 45-55 ℃ for 65-75 h, carrying out solid-liquid separation to obtain solid residues and in-situ enzyme hydrolysis liquid, and carrying out oil production fermentation after the pH of the in-situ enzyme hydrolysis liquid is adjusted.
  2. 2. The method of claim 1, wherein the agricultural and forestry waste is selected from more than one of bagasse, wheat straw, and corn stover.
  3. 3. The method according to claim 1 or 2, wherein the mass ratio of the agricultural and forestry waste to the aqueous solution containing the auxiliary agent and the organic acid is 1:6-1:12.
  4. 4. The method according to claim 2, wherein the agricultural and forestry waste is bagasse, the pretreatment condition is 160 ℃ to 170 ℃ and the reaction is 1.0 to 1.5 h, the mass fraction of the organic acid in the aqueous solution containing the auxiliary agent and the organic acid is 1.0 to 1.5%, and the mass fraction of the auxiliary agent is 0.5%.
  5. 5. The method according to claim 1 or 2, wherein the organic acid is selected from one of oxalic acid, acetic acid, levulinic acid and succinic acid.
  6. 6. The method of claim 5, wherein the organic acid is levulinic acid or succinic acid, and no auxiliary agent is added to the aqueous solution.
  7. 7. The method according to claim 1, wherein the temperature is reduced to 50 ℃ after the completion of the reaction, 5-25 mg/g of cellulase enzyme as starting material is added thereto, and 24-72 h is hydrolyzed at 50 ℃.
  8. 8. The method according to claim 1, wherein the specific steps of carrying out oleaginous fermentation after regulating the pH of the in-situ enzyme hydrolysate are that the oleaginous yeast strain is transferred to a seed culture medium from an inclined plane, the oleaginous yeast strain is activated for 24-36 h, the in-situ enzyme hydrolysate is regulated to pH5.0-7.0 to be used as a fermentation culture medium, the activated strain is inoculated into the fermentation culture medium with an inoculation amount of 5% -10%, the strain is centrifuged or filtered after fermentation at 25-35 ℃ for 84-120 h, microbial oil is extracted by an acid heating method or direct oil extraction, and the seed culture medium consists of raw materials with the mass percentage of 2% glucose, 1% yeast powder, 1% peptone and the balance deionized water.
  9. 9. The method of claim 8, wherein the oleaginous yeast is selected from more than one of rhodotorula glutinis, candida Trichosporon cutaneum, cryptococcus Cryptococcus albidus, yarrowia lipolytica Yarrowia lipolytica, rhodotorula Rhodosporidium torulodides, rhodotorula Lipomyces starkeyi, candida Cutaneotrichosporon dermatis, candida viscosa Trichosporon mucoides.
  10. 10. The method according to claim 8, wherein the pH of the enzymatic hydrolysate is adjusted to 5.0-7.0 by adding NaOH, ca (OH) 2 or CaO without further detoxification steps.

Description

Method for coupling in-situ enzymatic hydrolysis of agricultural and forestry waste through low-concentration auxiliary agent assisted low-organic acid pretreatment Technical Field The invention relates to the technical field of biomass energy conversion, in particular to a method for coupling in-situ enzymatic hydrolysis of agricultural and forestry waste pretreated with low-concentration auxiliary agent and auxiliary low-organic acid. Background In the process of converting agricultural and forestry wastes into energy chemicals, one step which is critical is to hydrolyze cellulose and hemicellulose in raw materials into fermentable sugars such as five-carbon sugar and six-carbon sugar, and then to prepare liquid fuels such as microbial oil, ethanol and butanol through biological fermentation. The conventional pretreatment method of lignocellulose biomass comprises the steps of 1) carrying out solid-liquid separation after hemicellulose removal by acid pretreatment, wherein hemicellulose hydrolysate xylose, arabinose or xylooligosaccharide is further utilized in pretreatment liquid, cellulose is further hydrolyzed by pretreatment residues under the action of cellulase to obtain glucose which is present in enzyme hydrolysate, the rest unhydrolyzed cellulose and lignin are in hydrolysis residues, liquid after solid-liquid separation is used for subsequent fermentation, five-carbon sugar and six-carbon sugar are respectively present in the pretreatment liquid and the enzyme hydrolysate, the solid content of enzyme hydrolysis is generally not more than 15% (Xiao et al,2004a,Kristensen et al,2009), the sugar concentration in the pretreatment liquid and the enzyme hydrolysate is generally not more than 30g/L, the subsequent fermentation needs concentration, otherwise, the sugar concentration is too low, the production efficiency is reduced, and the equipment investment is increased. 2) Lignin is preferentially treated by alkali/solvent pretreatment to remove lignin, and then enzyme hydrolysis is carried out to obtain fermentable sugar. The inorganic acid and alkali in the above methods 1) and 2) are liable to cause environmental pollution, and the solvent in the method 2) is liable to remain in the pretreatment slag to affect the enzyme activity and subsequent fermentation activity of the enzyme hydrolysis. In recent years, more and more researchers consider that lignocellulose biomass is subjected to synergistic pretreatment by using hydrothermal, low-organic acid and auxiliary agent and then is subjected to enzymatic hydrolysis, and an enzymatic hydrolysate is used for producing liquid fuels such as ethanol, grease and butanol by downstream fermentation. However, in the separation process of the solid phase product, because lignocellulose has strong water absorption (usually more than 50% of water content), no matter the hemicellulose is removed first or the lignin is pretreated, a large amount of hydrolysate (pentose or oligosaccharide obtained by hydrolyzing the hemicellulose) or solvent is taken away by the separated solid phase product, and a washing step is needed to recover more byproducts, so that the process is long and the investment is large. To solve the above problems, a method for pretreating biomass by using a solvent-coupled acid or alkali in combination with an enzyme pretreatment, for example, ZL 202211532425.8 discloses a method for pretreating biomass by using a glycerol formal-catalyst-aqueous solution, wherein the glycerol formal is 50-100% and the catalyst is a soluble acid (sulfuric acid, hydrochloric acid, formic acid or p-toluenesulfonic acid), alkali (sodium hydroxide, potassium hydroxide, ethylenediamine or acetamide) or salt (FeCl 3、Al2（SO4）3Cl3、Na3PO4 or CH 3 COONa). The method can separate hemicellulose, cellulose and lignin, and although the subsequent enzyme hydrolysis efficiency is high, the solvent and water are difficult to completely remove due to certain intersolubility, and glycerol formal or catalyst residues in the hemicellulose hydrolysis liquid serving as a fermentation substrate are easy to inhibit the subsequent fermentation. The process for recycling hemicellulose and lignin requires multiple steps of solid-liquid separation, pH adjustment, solvent washing hydrolysis slag and the like, and has long flow, and in addition, 50-100% of organic solvents such as glycerol formal, tetrahydrofurfuryl alcohol, gamma-valerolactone and the like are used in large amounts, and the high saturated vapor pressure of the solvents leads to high reaction pressure, so that the reactor is high in manufacturing cost, and the adopted inorganic acid, alkali and salt have serious corrosion to equipment. US20220298531A1 discloses that biomass and water are mixed in a continuous countercurrent extrusion/reactor, subjected to a certain time and temperature treatment, and subjected to solid-liquid separation to obtain a solid phase substance rich in cellulose and a liquid phase substance rich in