CN115125749B - Process for pretreatment of straw biomass by mechanical strengthening ammonia method - Google Patents
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- C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
- C12P7/00—Preparation of oxygen-containing organic compounds
- C12P7/40—Preparation of oxygen-containing organic compounds containing a carboxyl group including Peroxycarboxylic acids
- C12P7/56—Lactic acid
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- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
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Abstract
The invention discloses a technology for pretreatment of straw biomass by a mechanical strengthening ammonia method, which comprises the following steps: s1: treating straw lignocellulose biomass and pretreatment liquid containing ammonia water and inorganic ammonium salt in double-screw equipment; s2: and (3) carrying out heat preservation reaction on the material obtained in the step (S1), and carrying out solid-liquid separation to obtain solid fibers containing heald fibers and black liquor containing lignin. The pretreatment liquid is formed by compounding ammonia water and inorganic ammonium salt, so that physical and chemical bonds between lignin and holocellulose can be effectively cut off in the pretreatment operation process, the removal rate of lignin under mild conditions is improved, the polycondensation of lignin under conventional high-temperature and high-pressure cooking conditions is avoided, and lignin components with complete structure preservation are extracted; at the same time, the retention rate of cellulose and hemicellulose is also higher.
Description
Technical Field
The invention relates to the fields of biochemical engineering and biological energy, in particular to a process for preparing lactic acid by mechanically strengthening ammonia pretreatment of straw biomass and a process for preparing lactic acid by mechanically strengthening ammonia pretreatment of straw biomass.
Background
With the exhaustion of global fossil energy, and the use of fossil energy, greenhouse gases, toxic substances and standard pollutants are released, resulting in environmental pollution and adverse climate change effects. Therefore, development of renewable, sustainable green resources is urgent.
Lignocellulosic biomass, which is the most abundant renewable resource on earth, is composed of mostly cellulose, hemicellulose, lignin, and minor amounts of other minor ingredients. Wherein, the cellulose and hemicellulose can be degraded into monosaccharide components to provide carbon source for lactic acid fermentation, which effectively reduces the environmental pollution problem caused by petroleum derived chemicals, and reduces the cost and the grain competing problem caused by starch fermentation in grain crops (such as rice, cassava or sorghum). But lignin composed of guaiacyl, syringyl and p-hydroxyphenyl subunits is linked by C-O, C-C and H bonds and Van der Waals forces, forming a intractable, crystalline three-dimensional structure that resists digestion by microorganisms. The complex and stubborn structure of the lignocellulose can be effectively destroyed by the pretreatment technology, so that the lignocellulose can be efficiently utilized.
Technologies for pretreatment of lignocellulosic biomass mainly include physical, chemical, and biological pretreatment, and the like. For example, the application CN105296329a discloses a device and a method for continuously preprocessing lignocellulose materials by utilizing microwave-dilute acid steam explosion, but the method has high temperature and high pressure in the preprocessing process, increases the energy consumption cost, and has higher requirements on acid resistance and pressure resistance of equipment; the Chinese invention application CN110760552A discloses a pretreatment method for improving the saccharification efficiency of lignocellulose, but the pretreatment method has long pretreatment period, high production cost and complex process; chinese application CN103993053a discloses a method for pretreatment of biomass by coupling water and ammonia, but the method has high energy consumption and discontinuous process; the Chinese patent application CN103255659A discloses a method for treating lignocellulose biomass by ammonia combined with dilute alkali at normal pressure, but the method has the advantages that the chemical reagent dosage is large, a large amount of high-salt wastewater is generated at the same time, and removed lignin components are not recovered, so that the method is contrary to the concept of green chemistry. The mechanical strengthening ammonia pretreatment can effectively remove lignin components, get rid of the traditional intermittent reaction system, and reduce the energy consumption in the pretreatment process. Meanwhile, the production of byproducts in the pretreatment process and the equipment requirement can be effectively reduced under the conditions of normal temperature and normal pressure.
Thus, developing an economical, efficient, green and continuous pretreatment process remains a key challenge for lignocellulosic conversion technology.
Disclosure of Invention
The invention aims to: aiming at the defects of the prior art, the invention provides a double-screw pretreatment process for straw lignocellulose biomass, which aims to solve the problems that sugar is degraded into byproducts in the prior pretreatment process, saccharification yield is influenced, microbial fermentation inhibitor is produced, and lignin is polymerized under the severe conditions of high temperature and high pressure, so that a good biological substrate is provided for the subsequent enzymolysis saccharification fermentation production of L-lactic acid.
The invention also solves the technical problem of providing a process for preparing lactic acid by pretreatment of straw biomass by a mechanical strengthening ammonia method.
In order to solve the first technical problem, the invention discloses a technology for pretreatment of straw biomass by a mechanical strengthening ammonia method, which comprises the following steps:
s1: treating straw lignocellulose biomass and pretreatment liquid containing ammonia water and inorganic ammonium salt in double-screw equipment;
s2: and (3) carrying out heat preservation reaction on the material obtained in the step (S1), and carrying out solid-liquid separation to obtain solid fibers containing heald fibers and black liquor containing aminated lignin.
In step S1, the straw lignocellulose biomass includes, but is not limited to, any one or a combination of several of wheat straw, corn straw, rice straw, sorghum straw, bagasse, corn cob, switchgrass, reed and rape.
In the step S1, the particle size of the straw lignocellulose biomass is 3-5cm.
In the step S1, the pretreatment liquid is an aqueous solution containing 5 to 30% w/w of ammonia water and 0.1 to 2% w/w of inorganic ammonium salt, preferably an aqueous solution containing 20 to 30% w/w of ammonia water and 0.5 to 1.5% w/w of inorganic ammonium salt, and more preferably an aqueous solution containing 25% w/w of ammonia water and 1% w/w of inorganic ammonium salt.
In step S1, the inorganic ammonium salt is any one or a combination of several of sodium hydrogen phosphate, ammonium carbonate, ammonium bicarbonate, ammonium sulfate and ammonium chloride, preferably sodium hydrogen phosphate.
In the step S1, the dosage of the pretreatment liquid is 2-10 times of the mass of the dry straw lignocellulose biomass.
In step S1, the processing parameters of the twin-screw apparatus are: the rotating speed of the screw is 100-300 r/min, preferably 200r/min; the feeding speed is 15-25 kg/h, preferably 20kg/h.
In the step S2, the temperature of the heat preservation reaction is 80-140 ℃.
In the step S2, the time of the heat preservation reaction is 0.5-5 h.
Through the process, the retention rate of cellulose in the fixed component is more than 65%, the retention rate of hemicellulose in the fixed component is more than 65%, and the content of lignin in the black liquor is more than 50%.
In order to solve the second technical problem, the invention discloses a process for preparing lactic acid by pretreatment of straw biomass by a mechanical strengthening ammonia method, wherein an enzymolysis product of solid fibers obtained by pretreatment of straw lignocellulose biomass by the mechanical strengthening ammonia method is used as a carbon source of a fermentation medium in the process of producing lactic acid by fermentation.
The preparation method of the carbon source in the fermentation medium comprises the following steps:
s1: treating straw lignocellulose biomass and pretreatment liquid containing ammonia water and inorganic ammonium salt in double-screw equipment;
s2: carrying out heat preservation reaction on the material obtained in the step S1, and carrying out solid-liquid separation to obtain solid fibers containing heald fibers and black liquor containing aminated lignin;
s3: and (3) in a buffer solution, carrying out enzymolysis on the solid fiber obtained in the step (S2) by trichoderma reesei cellulase and xylanase, and carrying out solid-liquid separation, wherein the obtained supernatant is used as a carbon source in a fermentation medium for producing L-lactic acid by fermentation.
In step S1, the straw lignocellulose biomass includes, but is not limited to, any one or a combination of several of wheat straw, corn straw, rice straw, sorghum straw, bagasse, corn cob, switchgrass, reed and rape.
In the step S1, the particle size of the straw lignocellulose biomass is 3-5cm.
In the step S1, the pretreatment liquid is an aqueous solution containing 5 to 30% w/w of ammonia water and 1 to 20% w/w of inorganic ammonium salt, preferably an aqueous solution containing 20 to 30% w/w of ammonia water and 5 to 15% w/w of inorganic ammonium salt, and more preferably an aqueous solution containing 25% w/w of ammonia water and 10% w/w of inorganic ammonium salt.
In step S1, the inorganic ammonium salt is any one or a combination of several of sodium hydrogen phosphate, ammonium carbonate, ammonium bicarbonate, ammonium sulfate and ammonium chloride, preferably sodium hydrogen phosphate.
In the step S1, the dosage of the pretreatment liquid is 2-10 times of the mass of the dry straw lignocellulose biomass.
In step S1, the processing parameters of the twin-screw apparatus are: the rotating speed of the screw is 100-300 r/min, preferably 200r/min; the feeding speed is 15-25 kg/h, preferably 20kg/h.
In the step S2, the temperature of the heat preservation reaction is 80-140 ℃.
In the step S2, the time of the heat preservation reaction is 0.5-5 h.
In step S3, the buffer is 5mM sodium citrate buffer.
In the step S3, the adding amount of the Trichoderma reesei cellulase is 10-30 FPU/g solid fibers, preferably 20FPU/g solid fibers.
In the step S3, the xylanase is added in an amount of 40-60 IU/g solid fiber, preferably 50IU/g solid fiber.
In the step S3, the dosage ratio of the solid fiber to the buffer solution is 1 (5-15) g/L, preferably 1:10g/L.
In the step S3, the enzymolysis temperature is 40-60 ℃, preferably 50 ℃; the enzymolysis time is 36-60 hours, preferably 40-56 hours, and more preferably 48 hours.
Wherein the fermentation medium further comprises a nitrogen source; the nitrogen source is yeast extract and/or corn steep liquor dry powder, preferably yeast extract and corn steep liquor dry powder; preferably, the yeast extract and the corn steep liquor dry powder are added to have the concentration of 1/14 to 1/34 and 1/40 to 1/60 of the concentration of glucose in the supernatant fluid respectively; preferably, the yeast extract and the corn steep liquor dry powder are added to a concentration of 1/18 to 1/25 and 1/48 to 1/52, respectively, of the glucose concentration in the supernatant.
Wherein the fermentation medium further comprises an inorganic salt; the inorganic salt is ammonium sulfate, monopotassium phosphate, magnesium sulfate heptahydrate, magnesium sulfate monohydrate and ferrous sulfate heptahydrate; preferably, the concentrations of the components are as follows: 2-4 g/L of ammonium sulfate, 0.12-0.32 g/L of monopotassium phosphate, 0.3-0.5 g/L of magnesium sulfate heptahydrate, 0.01-0.05 g/L of manganese sulfate monohydrate and 0.01-0.05 g/L of ferrous sulfate heptahydrate; preferably, the concentrations of the components are as follows: 3g/L of ammonium sulfate, 0.22g/L of monopotassium phosphate, 0.4g/L of magnesium sulfate heptahydrate, 0.03g/L of manganese sulfate monohydrate and 0.03g/L of ferrous sulfate heptahydrate.
The method for producing the L-lactic acid by fermentation comprises the steps of inoculating bacillus coagulans bacterial liquid into the fermentation medium, and fermenting to obtain fermentation liquor containing the L-lactic acid.
Wherein the bacillus coagulans is bacillus coagulans ACCC 10229, and the bacillus coagulans is the existing bacillus.
Wherein, the bacillus coagulans bacterial liquid is inoculated in the fermentation culture medium in a volume ratio of 5-20%, and preferably in a volume ratio of 10%.
Wherein the temperature of the fermentation is 40-60 ℃, preferably 50 ℃; the rotation speed of the fermentation is 100-200 rpm, preferably 150rpm; the fermentation time is 62-82 h, preferably 72h.
The beneficial effects are that: compared with the prior art, the invention has the following advantages:
1. the pretreatment liquid is formed by compounding ammonia water and inorganic ammonium salt, so that the physicochemical bond between lignin and holocellulose is effectively cut off in the pretreatment operation process, the removal rate of lignin under mild conditions is improved, the polycondensation of lignin under conventional high-temperature and high-pressure cooking conditions is avoided, and lignin components with complete structure preservation are extracted; at the same time, the retention rate of cellulose and hemicellulose is also higher.
2. The invention uses pretreated sugar solution after the hydrolysis and saccharification of the comprehensive cellulose, supplements nitrogen source and inorganic salt, and inoculates bacillus coagulans for fermentation to produce L-lactic acid, thereby greatly improving the concentration and conversion rate of the L-lactic acid.
3. The invention realizes continuous treatment process, reduces water consumption in the process of high solid-liquid ratio, reduces exogenous heating energy consumption, and reduces production cost from multiple aspects.
4. The invention realizes continuous operation of the pretreatment system, gets rid of the traditional intermittent reaction system and improves the production efficiency.
5. The continuous pretreatment process provided by the invention enables the efficient recovery of the holocellulose in the straw to be used for the L-lactic acid fermentation reaction after further enzymolysis saccharification, and simultaneously can efficiently recover lignin components with complete structures, thereby realizing the efficient utilization of all components of lignocellulose.
Drawings
The foregoing and/or other advantages of the invention will become more apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings and detailed description.
FIG. 1 is a two-dimensional nuclear magnetic resonance of lignin.
Fig. 2 is a microscopic image of the holocellulose.
Detailed Description
The experimental methods described in the following examples are all conventional methods unless otherwise specified; the reagents and materials, unless otherwise specified, are commercially available.
The detection method for chemical component analysis of biomass in the following examples uses the National Renewable Energy Laboratory (NREL) method, and the detection steps are as follows:
1) Adding 300+ -10 mg into 3.00+ -0.01 mL (or 4.92+ -0.01 g) of 72% sulfuric acid, mixing thoroughly, and placing into 30+ -3 water bath shaker for 60+ -5 min;
2) 84.00 + -0.04 mL deionized water was added and the acid was diluted to a concentration of 4%. Placed in an autoclave and treated at 121℃for 1h. After autoclave cycle is completed, allowing the hydrolyzate to slowly cool to near room temperature, and then removing the lid;
3) Vacuum filtering the autoclave hydrolysis solution through a previously weighed filter crucible, collecting filtrate for determination of acid soluble lignin and carbohydrates;
4) At least 50mL of fresh deionized water rinse solids, dry crucible and acid insoluble disability at 105±3 ℃ until a constant weight is reached, remove the sample from oven and cool in the dryer. The crucible and residue were then placed in a muffle furnace at 575.+ -. 25 ℃ for 24.+ -. 6 hours.
The lignocellulose raw material adopted in the following examples is wheat straw, the cellulose content in the wheat straw is 34.56wt%, the hemicellulose content is 21.46wt%, and the lignin content is 23.13wt%.
The enzyme activities of the Trichoderma reesei cellulase and xylanase added in the following examples were 260FPU/ml and 50IU/ml, respectively.
Trichoderma reesei cellulase activity is defined as: the amount of enzyme required to release 1. Mu. Mol of reducing sugar per minute is expressed as FPU/mL;
Xylanase activity is defined as: mu mol of reducing sugar produced per minute per mL of crude enzyme used for hydrolysis is expressed as IU/mL.
The bacillus coagulans ACCC 10229 bacterial liquid in the following examples was prepared as follows:
1) Taking a bacillus coagulans ACCC 10229 glycerol strain preserved at-80 ℃, adding a liquid seed culture medium with the volume of 20 times, and culturing for 12 hours at 50 ℃ and 150rpm without adding calcium carbonate into the culture medium, wherein the culture medium is recorded as a bacterium 1;
2) Inoculating bacteria 1 cultured at 50deg.C at 150rpm for 12 hr to solid seed culture medium containing calcium carbonate, wherein the concentration of calcium carbonate is 1/2 of glucose concentration, culturing at 50deg.C at 150rpm for 12-24 hr, and recording as bacteria 2;
3) Inoculating single bacterial colony growing in the bacterium 2 to a liquid seed culture medium added with calcium carbonate, and culturing for 12 hours at 50 ℃ and 150rpm at the concentration of 1/2 of the calcium carbonate and the glucose concentration to obtain bacillus coagulans ACCC 10229 bacterial liquid.
Wherein the liquid seed culture medium comprises the following formula: glucose 20g/L, yeast extract 2g/L, corn steep liquor dry powder 2.5g/L, ammonium chloride 1g/L, anhydrous magnesium sulfate 0.2g/L, pH 7.0, sterilizing 115 ℃ for 15min.
Wherein the solid seed culture medium comprises the following formula: glucose 20g/L, yeast extract 2g/L, corn steep liquor dry powder 2.5g/L, ammonium chloride 1g/L, anhydrous magnesium sulfate 0.2g/L, agar powder 16g/L, pH 7.0, sterilizing 115 ℃ for 15min.
The yield of L-lactic acid in the following examples was calculated as follows:
C L-LA l-lactic acid concentration at the end of fermentation
C G0 Fermentation initial glucose concentration
C G72 Glucose concentration at 72h after fermentation
1.04-correction coefficient of L-lactic acid.
The processing parameters of the twin screws in the following examples are: the rotating speed of the screw is 200r/min, and the feeding speed is 20kg/h.
Example 1
Taking dry wheat straw raw material, mechanically crushing the dry wheat straw raw material into 3-5cm fragments to serve as lignocellulose raw material for pretreatment, adopting tap water as impregnating solution, and heating the solution to 90 ℃. The twin screw device was started and heated steeping liquor and wheat straw pieces were simultaneously and continuously conveyed to the twin screw through the feed hopper, during which a pretreatment liquor 7 times the mass of the dry material, comprising 25% W/W aqueous ammonia, 1.0% W/W sodium hydrogen phosphate, was pumped. The wheat straw is subjected to heat preservation reaction for 1h at 130 ℃ in the screw by adjusting the frequency of a double-screw motor. And (3) conveying the materials subjected to the heat preservation reaction into a single-screw pulp extruder for solid-liquid separation, so as to obtain the fully-mechanized cellulose rich in cellulose and hemicellulose components and the alkaline black liquor containing hydrolyzed lignin.
The retention rate of the solid cellulose obtained after pretreatment is 91.03%, the retention rate of hemicellulose is 71.30%, and the yield of lignin in black liquor is 67.49%.
FIG. 1 is a graph of nuclear magnetic characterization of lignin in the resulting alkaline black liquor, wherein ferulic acid amide (FA 6, δC/δH 123.1/7.20) was identified in lignin, indicating that ester-linked ferulic acid has been grafted with nitrogen. Fig. 2 is a micrograph of the resulting fully-mechanized cellulose. As can be seen from fig. 1, the lignin component structure obtained after pretreatment by twin screws in combination with ammonia water remains intact. As can be seen from fig. 2, the fully-mechanized cellulose component obtained by the twin-screw combined with the pretreatment of ammonia water has a fluffy structure and shows a complete fiber-like structure without obvious fragmentation.
Straw L-lactic acid fermentation preparation:
(a) The heald cellulose obtained above was mixed with 5mM sodium citrate buffer at 1: mixing at a solid-liquid ratio of 10g/L, adding 20FPU/g of holocellulose and 50IU/g of holocellulose respectively, performing enzymolysis saccharification for 48h at 50 ℃, and performing solid-liquid separation at 10000rpm for 5min to obtain supernatant as enzymolysis sugar solution.
(b) The conversion rate of cellulose in the enzymolysis sugar solution is 92.50 percent by HPLC detection, the concentration of glucose is 59.09g/L, 2.46g/L of yeast extract and 1.18g/L of corn steep liquor dry powder are added into the enzymolysis sugar solution as nitrogen sources of a fermentation medium based on the concentration of glucose, and 3g/L of ammonium sulfate, 0.22g/L of monopotassium phosphate, 0.4g/L of magnesium sulfate heptahydrate, 0.03g/L of manganese sulfate monohydrate and 0.03g/L of ferrous sulfate heptahydrate are used as inorganic salts.
(c) Sterilizing the compounded mixture at 115 ℃ for 15min.
(d) Bacillus coagulans ACCC 10229 bacterial liquid with absorbance at OD600nm of 1.0 is inoculated into the compound mixture according to the volume ratio of 10 percent, and fermentation is carried out for 72 hours at 50 ℃ and 150rpm, thus obtaining fermentation liquor containing L-lactic acid.
And (3) carrying out HPLC detection on the lactic acid fermentation liquid to obtain L-lactic acid produced by fermenting straw lignocellulose as a raw material, wherein the concentration of the L-lactic acid produced in the sugar liquid is 53.01g/L, and the conversion rate of the L-lactic acid produced by sugar fermentation is 98.01%.
Example 2
Taking dry wheat straw raw material, mechanically crushing the dry wheat straw raw material into 3-5cm fragments to serve as lignocellulose raw material for pretreatment, adopting tap water as impregnating solution, and heating the solution to 90 ℃. The twin screw device was started and heated steeping liquor and wheat straw pieces were simultaneously and continuously conveyed to the twin screw through the feed hopper, during which a pretreatment liquor 7 times the mass of the dry material, comprising 25% W/W aqueous ammonia, 1.0% W/W sodium hydrogen phosphate, was pumped. The wheat straw is subjected to heat preservation reaction for 3 hours at 90 ℃ in the screw by adjusting the frequency of a double-screw motor. And (3) conveying the materials subjected to the heat preservation reaction into a single-screw pulp extruder for solid-liquid separation, so as to obtain the fully-mechanized cellulose rich in cellulose and hemicellulose components and the alkaline black liquor containing hydrolyzed lignin.
The retention rate of the solid cellulose obtained after pretreatment is 86.44%, the retention rate of hemicellulose is 67.41%, and the yield of lignin in black liquor is 58.31%.
And (3) preparing straw lactic acid fermentation:
(a) The heald cellulose obtained above was mixed with 5mM sodium citrate buffer at 1: mixing at a solid-liquid ratio of 10g/L, adding 20FPU/g of holocellulose and 50IU/g of holocellulose respectively, performing enzymolysis saccharification for 48h at 50 ℃, and performing solid-liquid separation at 10000rpm for 5min to obtain supernatant as enzymolysis sugar solution.
(b) The conversion rate of cellulose in the enzymolysis sugar solution is 88.31 percent by HPLC detection, the concentration of glucose is 56.49g/L, 2.35g/L of yeast extract and 1.13g/L of corn steep liquor dry powder are added into the enzymolysis sugar solution as nitrogen sources of a fermentation medium based on the concentration of glucose, and 3g/L of ammonium sulfate, 0.22g/L of monopotassium phosphate, 0.4g/L of magnesium sulfate heptahydrate, 0.03g/L of manganese sulfate monohydrate and 0.03g/L of ferrous sulfate heptahydrate are used as inorganic salts.
(c) Sterilizing the compounded mixture at 115 ℃ for 15min.
(d) Bacillus coagulans ACCC 10229 bacterial liquid with absorbance at OD600nm of 1.0 is inoculated into the compound mixture according to the volume ratio of 10 percent, and fermentation is carried out for 72 hours at 50 ℃ and 150rpm, thus obtaining fermentation liquor containing L-lactic acid.
And (3) carrying out HPLC detection on the lactic acid fermentation liquid to obtain L-lactic acid which is produced by fermenting straw lignocellulose as a raw material, wherein the concentration of the L-lactic acid produced in the sugar liquid is detected to be 48.75g/L by HPLC, and the conversion rate of the L-lactic acid produced by sugar fermentation is 89.47%.
Example 3
Taking dry wheat straw raw material, mechanically crushing the dry wheat straw raw material into 3-5cm fragments to serve as lignocellulose raw material for pretreatment, adopting tap water as impregnating solution, and heating the solution to 90 ℃. The twin-screw device is started, the heated impregnating solution and the wheat straw fragments are simultaneously and continuously conveyed to the twin-screw through the feeding hopper, and a pretreatment solution which is 3 times of the mass of the dried materials is pumped in during the period, and the pretreatment solution comprises 25% of W/W ammonia water and 1.0% of W/W sodium hydrogen phosphate. The wheat straw is subjected to heat preservation reaction for 3 hours at 130 ℃ in the screw by adjusting the frequency of a double-screw motor. And (3) conveying the materials subjected to the heat preservation reaction into a single-screw pulp extruder for solid-liquid separation, so as to obtain the fully-mechanized cellulose rich in cellulose and hemicellulose components and the alkaline black liquor containing hydrolyzed lignin.
The retention rate of the solid cellulose obtained after pretreatment is 86.58%, the retention rate of hemicellulose is 71.57%, and the yield of lignin in black liquor is 57.85%.
And (3) preparing straw lactic acid fermentation:
(a) The heald cellulose obtained above was mixed with 5mM sodium citrate buffer at 1: mixing at a solid-liquid ratio of 10g/L, adding 20FPU/g of holocellulose and 50IU/g of holocellulose respectively, performing enzymolysis saccharification for 48h at 50 ℃, and performing solid-liquid separation at 10000rpm for 5min to obtain supernatant as enzymolysis sugar solution.
(b) The conversion rate of cellulose in the enzymolysis sugar solution is 90.09 percent by HPLC detection, the concentration of glucose is 54.83g/L, 2.28g/L of yeast extract and 1.10g/L of corn steep liquor dry powder are added into the enzymolysis sugar solution as nitrogen sources of a fermentation medium based on the concentration of glucose, and 3g/L of ammonium sulfate, 0.22g/L of monopotassium phosphate, 0.4g/L of magnesium sulfate heptahydrate, 0.03g/L of manganese sulfate monohydrate and 0.03g/L of ferrous sulfate heptahydrate are used as inorganic salts.
(c) Sterilizing the compounded mixture at 115 ℃ for 15min.
(d) Bacillus coagulans ACCC 10229 bacterial liquid with absorbance at OD600nm of 1.0 is inoculated into the compound mixture according to the volume ratio of 10 percent, and fermentation is carried out for 72 hours at 50 ℃ and 150rpm, thus obtaining fermentation liquor containing L-lactic acid.
And (3) carrying out HPLC detection on the lactic acid fermentation liquid to obtain L-lactic acid produced by fermenting straw lignocellulose as a raw material, wherein the concentration of the L-lactic acid produced in the sugar liquid is 50.79g/L, and the conversion rate of the L-lactic acid produced by sugar fermentation is 96.13%.
Example 4
Taking dry wheat straw raw material, mechanically crushing the dry wheat straw raw material into 3-5cm fragments to serve as lignocellulose raw material for pretreatment, adopting tap water as impregnating solution, and heating the solution to 90 ℃. The twin screw device was started and heated steeping liquor and wheat straw pieces were simultaneously and continuously conveyed to the twin screw through the feed hopper, during which a pretreatment liquor 3 times the mass of the dry material, comprising 25% W/W aqueous ammonia, 1.5% W/W sodium hydrogen phosphate, was pumped. The wheat straw is subjected to heat preservation reaction for 1h at 90 ℃ in the screw by adjusting the frequency of a double-screw motor. And (3) conveying the materials subjected to the heat preservation reaction into a single-screw pulp extruder for solid-liquid separation, so as to obtain the fully-mechanized cellulose rich in cellulose and hemicellulose components and the alkaline black liquor containing hydrolyzed lignin.
The retention rate of the solid cellulose obtained after pretreatment is 85.94%, the retention rate of hemicellulose is 65.92%, and the yield of lignin in black liquor is 51.13%.
And (3) preparing straw lactic acid fermentation:
(a) The heald cellulose obtained above was mixed with 5mM sodium citrate buffer at 1: mixing at a solid-liquid ratio of 10g/L, adding 20FPU/g of holocellulose and 50IU/g of holocellulose respectively, performing enzymolysis saccharification for 48h at 50 ℃, and performing solid-liquid separation at 10000rpm for 5min to obtain supernatant as enzymolysis sugar solution.
(b) The conversion rate of cellulose in the enzymolysis sugar solution is 88.35 percent by HPLC detection, the concentration of glucose is 54.93g/L, 2.39g/L of yeast extract and 1.10g/L of corn steep liquor dry powder are added into the enzymolysis sugar solution as nitrogen sources of a fermentation medium based on the concentration of glucose, and 3g/L of ammonium sulfate, 0.22g/L of monopotassium phosphate, 0.4g/L of magnesium sulfate heptahydrate, 0.03g/L of manganese sulfate monohydrate and 0.03g/L of ferrous sulfate heptahydrate are used as inorganic salts.
(c) Sterilizing the compounded mixture at 115 ℃ for 15min.
(d) Bacillus coagulans ACCC 10229 bacterial liquid with absorbance at OD600nm of 1.0 is inoculated into the compound mixture according to the volume ratio of 10 percent, and fermentation is carried out for 72 hours at 50 ℃ and 150rpm, thus obtaining fermentation liquor containing L-lactic acid.
And (3) carrying out HPLC detection on the lactic acid fermentation liquid to obtain L-lactic acid which is produced by fermenting straw lignocellulose as a raw material, wherein the concentration of the L-lactic acid produced in the sugar liquid is 44.59g/L, and the conversion rate of the L-lactic acid produced by sugar fermentation is 84.25%.
Example 5
Taking dry wheat straw raw material, mechanically crushing the dry wheat straw raw material into 3-5cm fragments to serve as lignocellulose raw material for pretreatment, adopting tap water as impregnating solution, and heating the solution to 90 ℃. Starting a double-screw device, and simultaneously and continuously conveying the heated impregnating solution and the wheat straw fragments to the double screw through a feeding hopper, wherein a pretreatment solution with the mass 3 times of that of the dried materials is pumped in during the period, and the pretreatment solution comprises 15% W/W ammonia water and 1.5W/W sodium hydrogen phosphate. The wheat straw is subjected to heat preservation reaction for 1h at 90 ℃ in the screw by adjusting the frequency of a double-screw motor. And (3) conveying the materials subjected to the heat preservation reaction into a single-screw pulp extruder for solid-liquid separation, so as to obtain the fully-mechanized cellulose rich in cellulose and hemicellulose components and the alkaline black liquor containing hydrolyzed lignin.
The retention rate of the solid cellulose obtained after pretreatment is calculated to be 90.11%, the retention rate of hemicellulose is 67.72%, and the yield of lignin in black liquor is 56.22%.
And (3) preparing straw lactic acid fermentation:
(a) The heald cellulose obtained above was mixed with 5mM sodium citrate buffer at 1: mixing at a solid-liquid ratio of 10g/L, adding 20FPU/g of holocellulose and 50IU/g of holocellulose respectively, performing enzymolysis saccharification for 48h at 50 ℃, and performing solid-liquid separation at 10000rpm for 5min to obtain supernatant as enzymolysis sugar solution.
(b) The conversion rate of cellulose in the enzymolysis sugar solution is 86.29 percent by HPLC detection, the concentration of glucose is 56.57g/L, 2.36g/L of yeast extract and 1.13g/L of corn steep liquor dry powder are added into the enzymolysis sugar solution as nitrogen sources of a fermentation medium based on the concentration of glucose, and 3g/L of ammonium sulfate, 0.22g/L of monopotassium phosphate, 0.4g/L of magnesium sulfate heptahydrate, 0.03g/L of manganese sulfate monohydrate and 0.03g/L of ferrous sulfate heptahydrate are used as inorganic salts.
(c) Sterilizing the compounded mixture at 115 ℃ for 15min.
(d) Bacillus coagulans ACCC 10229 bacterial liquid with absorbance at OD600nm of 1.0 is inoculated into the compound mixture according to the volume ratio of 10 percent, and fermentation is carried out for 72 hours at 50 ℃ and 150rpm, thus obtaining fermentation liquor containing L-lactic acid.
And (3) carrying out HPLC detection on the lactic acid fermentation liquid to obtain L-lactic acid which is produced by fermenting straw lignocellulose as a raw material, wherein the concentration of the L-lactic acid produced in the sugar liquid is 47.46g/L, and the conversion rate of the L-lactic acid produced by sugar fermentation is 86.97%.
Example 6
Taking dry wheat straw raw material, mechanically crushing the dry wheat straw raw material into 3-5cm fragments to serve as lignocellulose raw material for pretreatment, adopting tap water as impregnating solution, and heating the solution to 90 ℃. Starting a double-screw device, and simultaneously and continuously conveying the heated impregnating solution and the wheat straw fragments to the double screw through a feeding hopper, wherein a pretreatment solution with the mass 3 times of that of the dried materials is pumped in during the period, and the pretreatment solution comprises 15% W/W ammonia water and 1.0W/W sodium hydrogen phosphate. The wheat straw is subjected to heat preservation reaction for 1h at 130 ℃ in the screw by adjusting the frequency of a double-screw motor. And (3) conveying the materials subjected to the heat preservation reaction into a single-screw pulp extruder for solid-liquid separation, so as to obtain the fully-mechanized cellulose rich in cellulose and hemicellulose components and the alkaline black liquor containing hydrolyzed lignin.
The retention rate of the solid cellulose obtained after pretreatment is 87.31%, the retention rate of hemicellulose is 66.65%, and the yield of lignin in black liquor is 53.43%.
And (3) preparing straw lactic acid fermentation:
(a) The heald cellulose obtained above was mixed with 5mM sodium citrate buffer at 1: mixing at a solid-liquid ratio of 10g/L, adding 20FPU/g of holocellulose and 50IU/g of holocellulose respectively, performing enzymolysis saccharification for 48h at 50 ℃, and performing solid-liquid separation at 10000rpm for 5min to obtain supernatant as enzymolysis sugar solution.
(b) The conversion rate of cellulose in the enzymolysis sugar solution is 90.21 percent by HPLC detection, the concentration of glucose is 58.43g/L, 2.43g/L of yeast extract and 1.17g/L of corn steep liquor dry powder are added into the enzymolysis sugar solution as nitrogen sources of a fermentation medium based on the concentration of glucose, and 3g/L of ammonium sulfate, 0.22g/L of monopotassium phosphate, 0.4g/L of magnesium sulfate heptahydrate, 0.03g/L of manganese sulfate monohydrate and 0.03g/L of ferrous sulfate heptahydrate are used as inorganic salts.
(c) Sterilizing the compounded mixture at 115 ℃ for 15min.
(d) Bacillus coagulans ACCC 10229 bacterial liquid with absorbance at OD600nm of 1.0 is inoculated into the compound mixture according to the volume ratio of 10 percent, and fermentation is carried out for 72 hours at 50 ℃ and 150rpm, thus obtaining fermentation liquor containing L-lactic acid.
And (3) carrying out HPLC detection on the lactic acid fermentation liquid to obtain the L-lactic acid produced by fermenting straw lignocellulose as a raw material, wherein the concentration of the L-lactic acid produced in the sugar liquid is detected to be 49.12g/L by HPLC, and the conversion rate of the L-lactic acid produced by sugar fermentation is detected to be 87.05%.
Example 7
Taking dry wheat straw raw material, mechanically crushing the dry wheat straw raw material into 3-5cm fragments to serve as lignocellulose raw material for pretreatment, adopting tap water as impregnating solution, and heating the solution to 90 ℃. Starting a double-screw device, and simultaneously and continuously conveying the heated impregnating solution and the wheat straw fragments to the double screw through a feeding hopper, wherein a pretreatment solution with the mass 7 times of the mass of the dried materials is pumped in during the period, and the pretreatment solution comprises 15% W/W ammonia water and 1.5W/W sodium hydrogen phosphate. The wheat straw is subjected to heat preservation reaction for 3 hours at 130 ℃ in the screw by adjusting the frequency of a double-screw motor. And (3) conveying the materials subjected to the heat preservation reaction into a single-screw pulp extruder for solid-liquid separation, so as to obtain the fully-mechanized cellulose rich in cellulose and hemicellulose components and the alkaline black liquor containing hydrolyzed lignin.
The retention rate of the solid cellulose obtained after pretreatment is 82.42%, the retention rate of hemicellulose is 65.96%, and the yield of lignin in black liquor is 60.03%.
And (3) preparing straw lactic acid fermentation:
(a) The heald cellulose obtained above was mixed with 5mM sodium citrate buffer at 1: mixing at a solid-liquid ratio of 10g/L, adding 20FPU/g of holocellulose and 50IU/g of holocellulose respectively, performing enzymolysis saccharification for 48h at 50 ℃, and performing solid-liquid separation at 10000rpm for 5min to obtain supernatant as enzymolysis sugar solution.
(b) The conversion rate of cellulose in the enzymolysis sugar solution is 86.80 percent by HPLC detection, the concentration of glucose is 58.15g/L, 2.42g/L of yeast extract and 1.16g/L of corn steep liquor dry powder are added into the enzymolysis sugar solution as nitrogen sources of a fermentation medium based on the concentration of glucose, and 3g/L of ammonium sulfate, 0.22g/L of monopotassium phosphate, 0.4g/L of magnesium sulfate heptahydrate, 0.03g/L of manganese sulfate monohydrate and 0.03g/L of ferrous sulfate heptahydrate are used as inorganic salts.
(c) Sterilizing the compounded mixture at 115 ℃ for 15min.
(d) Bacillus coagulans ACCC 10229 bacterial liquid with absorbance at OD600nm of 1.0 is inoculated into the compound mixture according to the volume ratio of 10 percent, and fermentation is carried out for 72 hours at 50 ℃ and 150rpm, thus obtaining fermentation liquor containing L-lactic acid.
And (3) performing HPLC detection on the lactic acid fermentation liquid to obtain L-lactic acid produced by fermenting straw lignocellulose as a raw material, wherein the concentration of the L-lactic acid produced in the sugar liquid is detected to be 43.92g/L by HPLC, and the conversion rate of the L-lactic acid produced by sugar fermentation is 78.22%.
Example 8
Taking dry wheat straw raw material, mechanically crushing the dry wheat straw raw material into 3-5cm fragments to serve as lignocellulose raw material for pretreatment, adopting tap water as impregnating solution, and heating the solution to 90 ℃. Starting a double-screw device, and simultaneously and continuously conveying the heated impregnating solution and the wheat straw fragments to the double screw through a feeding hopper, wherein a pretreatment solution with the mass 7 times of the mass of the dried materials is pumped in during the period, and the pretreatment solution comprises 15% W/W ammonia water and 1.5W/W sodium hydrogen phosphate. The wheat straw is subjected to heat preservation reaction for 3 hours at 90 ℃ in the screw by adjusting the frequency of a double-screw motor. And (3) conveying the materials subjected to the heat preservation reaction into a single-screw pulp extruder for solid-liquid separation, so as to obtain the fully-mechanized cellulose rich in cellulose and hemicellulose components and the alkaline black liquor containing hydrolyzed lignin.
The retention rate of the solid cellulose obtained after pretreatment is 84.00%, the retention rate of hemicellulose is 65.52%, and the yield of lignin in black liquor is 61.08%.
And (3) preparing straw lactic acid fermentation:
(a) The heald cellulose obtained above was mixed with 5mM sodium citrate buffer at 1: mixing at a solid-liquid ratio of 10g/L, adding 20FPU/g of holocellulose and 50IU/g of holocellulose respectively, performing enzymolysis saccharification for 48h at 50 ℃, and performing solid-liquid separation at 10000rpm for 5min to obtain supernatant as enzymolysis sugar solution.
(b) The conversion rate of cellulose in the enzymolysis sugar solution is 84.95 percent by HPLC detection, the concentration of glucose is 52.93g/L, 2.21g/L of yeast extract and 1.06g/L of corn steep liquor dry powder are added into the enzymolysis sugar solution as nitrogen sources of a fermentation medium based on the concentration of glucose, and 3g/L of ammonium sulfate, 0.22g/L of monopotassium phosphate, 0.4g/L of magnesium sulfate heptahydrate, 0.03g/L of manganese sulfate monohydrate and 0.03g/L of ferrous sulfate heptahydrate are used as inorganic salts.
(c) Sterilizing the compounded mixture at 115 ℃ for 15min.
(d) Bacillus coagulans ACCC 10229 bacterial liquid with absorbance at OD600nm of 1.0 is inoculated into the compound mixture according to the volume ratio of 10 percent, and fermentation is carried out for 72 hours at 50 ℃ and 150rpm, thus obtaining fermentation liquor containing L-lactic acid.
And (3) carrying out HPLC detection on the lactic acid fermentation liquid to obtain L-lactic acid which is produced by fermenting straw lignocellulose as a raw material, wherein the concentration of the L-lactic acid produced in the sugar liquid is detected to be 41.16g/L by HPLC, and the conversion rate of the L-lactic acid produced by sugar fermentation is 80.00%.
Example 9
Taking dry wheat straw raw material, mechanically crushing the dry wheat straw raw material into 3-5cm fragments to serve as lignocellulose raw material for pretreatment, adopting tap water as impregnating solution, and heating the solution to 90 ℃. Starting a double-screw device, and simultaneously and continuously conveying the heated impregnating solution and the wheat straw fragments to the double screw through a feeding hopper, wherein a pretreatment solution with the mass 7 times of the mass of the dried materials is pumped in during the period, and the pretreatment solution comprises 15% W/W ammonia water and 0.5W/W sodium hydrogen phosphate. The wheat straw is subjected to heat preservation reaction for 1h at 130 ℃ in the screw by adjusting the frequency of a double-screw motor. And (3) conveying the materials subjected to the heat preservation reaction into a single-screw pulp extruder for solid-liquid separation, so as to obtain the fully-mechanized cellulose rich in cellulose and hemicellulose components and the alkaline black liquor containing hydrolyzed lignin.
The retention rate of the solid cellulose obtained after pretreatment is 87.35%, the retention rate of hemicellulose is 67.69%, and the yield of lignin in black liquor is 56.85%.
And (3) preparing straw lactic acid fermentation:
(a) The heald cellulose obtained above was mixed with 5mM sodium citrate buffer at 1: mixing at a solid-liquid ratio of 10g/L, adding 20FPU/g of holocellulose and 50IU/g of holocellulose respectively, performing enzymolysis saccharification for 48h at 50 ℃, and performing solid-liquid separation at 10000rpm for 5min to obtain supernatant as enzymolysis sugar solution.
(b) The conversion rate of cellulose in the enzymolysis sugar solution is 82.98 percent by HPLC detection, the concentration of glucose is 54.52g/L, 2.27g/L of yeast extract and 1.09g/L of corn steep liquor dry powder are added into the enzymolysis sugar solution as nitrogen sources of a fermentation medium based on the concentration of glucose, and 3g/L of ammonium sulfate, 0.22g/L of monopotassium phosphate, 0.4g/L of magnesium sulfate heptahydrate, 0.03g/L of manganese sulfate monohydrate and 0.03g/L of ferrous sulfate heptahydrate are used as inorganic salts.
(c) Sterilizing the compounded mixture at 115 ℃ for 15min.
(d) Bacillus coagulans ACCC 10229 bacterial liquid with absorbance at OD600nm of 1.0 is inoculated into the compound mixture according to the volume ratio of 10 percent, and fermentation is carried out for 72 hours at 50 ℃ and 150rpm, thus obtaining fermentation liquor containing L-lactic acid.
And (3) carrying out HPLC detection on the lactic acid fermentation liquid to obtain L-lactic acid which is produced by fermenting straw lignocellulose as a raw material, wherein the concentration of the L-lactic acid produced in the sugar liquid is 42.76g/L, and the conversion rate of the L-lactic acid produced by sugar fermentation is 81.42%.
Example 10
Taking dry wheat straw raw material, mechanically crushing the dry wheat straw raw material into 3-5cm fragments to serve as lignocellulose raw material for pretreatment, adopting tap water as impregnating solution, and heating the solution to 90 ℃. Starting a double-screw device, and simultaneously and continuously conveying the heated impregnating solution and the wheat straw fragments to the double screw through a feeding hopper, wherein a pretreatment solution with the mass 3 times of that of the dry materials is pumped in during the period, and the pretreatment solution comprises 15W/W ammonia water and 0.5W/W sodium hydrogen phosphate. The wheat straw is subjected to heat preservation reaction for 3 hours at 90 ℃ in the screw by adjusting the frequency of a double-screw motor. And (3) conveying the materials subjected to the heat preservation reaction into a single-screw pulp extruder for solid-liquid separation, so as to obtain the fully-mechanized cellulose rich in cellulose and hemicellulose components and the alkaline black liquor containing hydrolyzed lignin.
The retention rate of the solid cellulose obtained after pretreatment is 85.66%, the retention rate of hemicellulose is 68.62%, and the yield of lignin in black liquor is 53.07%.
And (3) preparing straw lactic acid fermentation:
(a) The heald cellulose obtained above was mixed with 5mM sodium citrate buffer at 1: mixing at a solid-liquid ratio of 10g/L, adding 20FPU/g of holocellulose and 50IU/g of holocellulose respectively, performing enzymolysis saccharification for 48h at 50 ℃, and performing solid-liquid separation at 10000rpm for 5min to obtain supernatant as enzymolysis sugar solution.
(b) The conversion rate of cellulose in the enzymolysis sugar solution is 80.39 percent by HPLC detection, the concentration of glucose is 53.66g/L, 2.24g/L of yeast extract and 1.07g/L of corn steep liquor dry powder are added into the enzymolysis sugar solution as nitrogen sources of a fermentation medium based on the concentration of glucose, and 3g/L of ammonium sulfate, 0.22g/L of monopotassium phosphate, 0.4g/L of magnesium sulfate heptahydrate, 0.03g/L of manganese sulfate monohydrate and 0.03g/L of ferrous sulfate heptahydrate are used as inorganic salts.
(c) Sterilizing the compounded mixture at 115 ℃ for 15min.
(d) Bacillus coagulans ACCC 10229 bacterial liquid with absorbance at OD600nm of 1.0 is inoculated into the compound mixture according to the volume ratio of 10 percent, and fermentation is carried out for 72 hours at 50 ℃ and 150rpm, thus obtaining fermentation liquor containing L-lactic acid.
And (3) performing HPLC detection on the lactic acid fermentation liquid to obtain L-lactic acid produced by fermenting straw lignocellulose as a raw material, wherein the concentration of the L-lactic acid produced in the sugar liquid is detected to be 38.53g/L by HPLC, and the conversion rate of the L-lactic acid produced by sugar fermentation is 74.58%.
Example 11
Taking dry wheat straw raw material, mechanically crushing the dry wheat straw raw material into 3-5cm fragments to serve as lignocellulose raw material for pretreatment, adopting tap water as impregnating solution, and heating the solution to 90 ℃. Starting a double-screw device, and simultaneously and continuously conveying the heated impregnating solution and the wheat straw fragments to the double screw through a feeding hopper, wherein a pretreatment solution with the mass 7 times of the mass of the dried materials is pumped in during the period, and the pretreatment solution comprises 25% W/W ammonia water and 0.5W/W sodium hydrogen phosphate. The wheat straw is subjected to heat preservation reaction for 1h at 90 ℃ in the screw by adjusting the frequency of a double-screw motor. And (3) conveying the materials subjected to the heat preservation reaction into a single-screw pulp extruder for solid-liquid separation, so as to obtain the fully-mechanized cellulose rich in cellulose and hemicellulose components and the alkaline black liquor containing hydrolyzed lignin.
The retention rate of the solid cellulose obtained after pretreatment is 87.93%, the retention rate of hemicellulose is 67.44%, and the yield of lignin in black liquor is 56.31%.
And (3) preparing straw lactic acid fermentation:
(a) The heald cellulose obtained above was mixed with 5mM sodium citrate buffer at 1: mixing at a solid-liquid ratio of 10g/L, adding 20FPU/g of holocellulose and 50IU/g of holocellulose respectively, performing enzymolysis saccharification for 48h at 50 ℃, and performing solid-liquid separation at 10000rpm for 5min to obtain supernatant as enzymolysis sugar solution.
(b) The conversion rate of cellulose in the enzymolysis sugar solution is 89.83 percent by HPLC detection, the concentration of glucose is 55.35g/L, 2.31g/L of yeast extract and 1.11g/L of corn steep liquor dry powder are added into the enzymolysis sugar solution as nitrogen sources of a fermentation medium based on the concentration of glucose, and 3g/L of ammonium sulfate, 0.22g/L of monopotassium phosphate, 0.4g/L of magnesium sulfate heptahydrate, 0.03g/L of manganese sulfate monohydrate and 0.03g/L of ferrous sulfate heptahydrate are used as inorganic salts.
(c) Sterilizing the compounded mixture at 115 ℃ for 15min.
(d) Bacillus coagulans ACCC 10229 bacterial liquid with absorbance at OD600nm of 1.0 is inoculated into the compound mixture according to the volume ratio of 10 percent, and fermentation is carried out for 72 hours at 50 ℃ and 150rpm, thus obtaining fermentation liquor containing L-lactic acid.
And (3) carrying out HPLC detection on the lactic acid fermentation liquid to obtain L-lactic acid which is produced by fermenting straw lignocellulose as a raw material, wherein the concentration of the L-lactic acid produced in the sugar liquid is detected to be 46.47g/L by HPLC, and the conversion rate of the L-lactic acid produced by sugar fermentation is detected to be 87.10%.
Example 12
The results of the same procedure as in example 1, except that sodium hydrogenphosphate was changed to other different inorganic ammonium salts, are shown in Table 1.
TABLE 1
For example 1
The difference is that the pretreatment liquid was replaced with 25% W/W ammonia alone, as in example 1.
The retention rate of the solid cellulose obtained after pretreatment is 58.89%, the retention rate of hemicellulose is 43.28%, and the yield of lignin in black liquor is 38.69%.
HPLC detection is carried out on the lactic acid fermentation liquid obtained by enzymolysis and saccharification, the cellulose conversion rate is 72.41%, the glucose concentration is 45.03g/L, the L-lactic acid is obtained after fermentation, the concentration is 29.61g/L, and the conversion rate of L-lactic acid generated by sugar fermentation is 65%.
Comparative example 2
The same as in example 1 was found to be different in that the pretreatment liquid was replaced with 1.0W/W sodium hydrogenphosphate alone.
The retention rate of the solid cellulose obtained after pretreatment is 58.66%, the retention rate of hemicellulose is 45.59%, and the yield of lignin in black liquor is 34.27%.
HPLC detection is carried out on the lactic acid fermentation liquid obtained by enzymolysis and saccharification, the cellulose conversion rate is 75.37%, the glucose concentration is 47.25g/L, the L-lactic acid is obtained after fermentation, the concentration is 25.82g/L, and the conversion rate of L-lactic acid generated by sugar fermentation is 56%.
Comparative example 3
The same as in example 1 was followed except that the pretreatment method was conducted using a high-temperature and high-pressure autoclave under the same conditions.
The retention rate of the solid cellulose obtained after pretreatment is 55.13%, the retention rate of hemicellulose is 48.66%, and the yield of lignin in black liquor is 25.33%.
HPLC detection is carried out on the lactic acid fermentation liquid obtained by enzymolysis and saccharification, the cellulose conversion rate is 75.60%, the glucose concentration is 49.82g/L, the L-lactic acid is obtained after fermentation, the concentration is 36.92g/L, and the conversion rate of L-lactic acid generated by sugar fermentation is 60.05%.
Comparative example 4
The difference is that the pretreatment liquid is a 30% w/w methanolic amine solution of organic base.
The retention rate of the solid cellulose obtained after pretreatment is 57.33%, the retention rate of hemicellulose is 45.37%, and the yield of lignin in black liquor is 35.26%.
HPLC detection is carried out on the lactic acid fermentation liquid obtained by enzymolysis and saccharification, the cellulose conversion rate is 76.88%, the glucose concentration is 48.57g/L, the L-lactic acid is obtained after fermentation, the concentration is 46.74g/L, and the conversion rate of L-lactic acid generated by sugar fermentation is 75.86%.
According to comparative analysis, the pretreatment liquid and the pretreatment method can better promote straw decomposition, obtain complete high-purity lignin structure and high-retention-rate comprehensive cellulose components, and respectively improve the retention rate of cellulose and hemicellulose by 25% and 15% under the same pretreatment condition. Meanwhile, the obtained holocellulose is used as a biological base material, is efficiently converted into L-lactic acid through enzymolysis saccharification, and can be further applied to various fields such as food, pharmacy, chemical industry and the like.
According to the invention, the pretreatment liquid prepared by compounding the sodium hydrogen phosphate and the ammonia water solution is matched with a double screw of continuous pretreatment equipment, so that effective separation of the holocellulose and the lignin is efficiently carried out under mild conditions, the lignin component with complete structure retention is obtained under the condition of ensuring the retention rate of the cellulose, the retention rates of the cellulose and the hemicellulose are both maintained to be above 85% and 55%, and the lignin yield is maintained to be above 65%. In addition, no external heating is needed in the pretreatment process, and the obtained fiber has no fragmentation and has an obvious fiber bundle structure. The pretreatment system has the feasibility of industrial amplification. The fully-mechanized cellulose obtained after pretreatment is hydrolyzed and saccharified, and then is efficiently converted into L-lactic acid through fermentation.
Lignocellulose such as corn stover, rice straw, sorghum straw, bagasse, corncob, switchgrass, reed, rape, etc. is similar to wheat straw, and can be treated and recycled by the same or similar method.
The invention provides a method and a thinking of a process for preparing lactic acid by mechanically strengthening ammonia pretreatment of straw biomass, and particularly the method and the way for realizing the technical scheme are numerous, the above is only a preferred embodiment of the invention, and it should be pointed out that a plurality of improvements and modifications can be made by those skilled in the art without departing from the principle of the invention, and the improvements and the modifications are also regarded as the protection scope of the invention. The components not explicitly described in this embodiment can be implemented by using the prior art.
Claims (5)
1. The technology for pretreating straw biomass by a mechanical strengthening ammonia method is characterized by comprising the following steps of:
s1: processing straw lignocellulose biomass and pretreatment liquid in double-screw equipment; the pretreatment liquid is an aqueous solution containing 20-30% w/w ammonia water and 0.5-1.5% w/w inorganic ammonium salt; the inorganic ammonium salt is sodium hydrogen phosphate; the consumption of the pretreatment liquid is 2-10 times of the mass of the straw lignocellulose biomass;
S2: carrying out heat preservation reaction on the material obtained in the step S1, and carrying out solid-liquid separation to obtain solid fibers containing heald fibers and black liquor containing lignin; the temperature of the heat preservation reaction is 80-140 ℃, and the time of the heat preservation reaction is 0.5-5 h.
2. The process of claim 1, wherein in step S1, the straw-based lignocellulosic biomass is any one or a combination of several of wheat straw, corn straw, rice straw, sorghum straw, bagasse, corn cob, switchgrass, reed, and canola.
3. The process according to claim 1, characterized in that in step S1, the particle size of the straw-based lignocellulosic biomass is 3-5cm.
4. The process according to claim 1, characterized in that in step S1, the processing parameters of the twin-screw device are: the rotating speed of the screw is 100-300 r/min, and the feeding speed is 15-25 kg/h.
5. A process for preparing lactic acid by pretreatment of straw biomass by a mechanical strengthening ammonia method, which is characterized in that an enzymolysis product of solid fibers obtained by the pretreatment of the straw biomass by the mechanical strengthening ammonia method in any one of claims 1-4 is used as a carbon source of a fermentation medium.
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