A method for co-production of lactic acid, xylitol and lignin from lignocellulosic feedstock

Abstract

The application discloses a method for co-production of lactic acid, xylitol and lignin from lignocellulose raw materials, and utilizes lignocellulose as raw materials to co-produce lactic acid, xylitol and lignin, which is beneficial to guarantee food safety, realize green and low-carbon development, solve the environmental problems caused by straw burning, and increase the income of farmers, and has good social and environmental benefits.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lactic acid, xylitol and lignin production, and particularly relates to a method for co-production of lactic acid, xylitol and lignin from lignocellulose raw material. BACKGROUND

[0002] Lactic acid can be used as a raw material for producing polylactic acid. Polylactic acid is a new type of biodegradable material, which has good biodegradability and can be completely degraded by microorganisms in nature, finally generating carbon dioxide and water without polluting the environment, which is very beneficial to environmental protection and is recognized as an environmentally friendly material.

[0003] Xylitol has a sweetness equivalent to sucrose, but only half the energy of sucrose, and its metabolism in the human body does not require the participation of insulin, so it is widely used in the medical, food and other industries. Xylitol is the first rare sugar in the world, and is a raw material for producing other rare sugars and synthesizing biopolymers, and is listed by the US Department of Energy as one of the 12 most competitive bio-based platform compounds.

[0004] Lignin is one of the main components of lignocellulose. Lignin can be widely used in the preparation of phenolic resin, polyurethane and other materials, and can be used as a filler to modify rubber, and can also be applied to carbon cellulose materials, surfactants, flocculants and the like, and has good application value.

[0005] At present, the raw materials of biochemicals (such as lactic acid, xylitol, etc.) mainly come from food crops (such as corn, etc.), and if they are developed on a large scale, they may pose a certain threat to China's food security. SUMMARY

[0006] The present application aims at the deficiencies in the prior art, and provides a method for co-production of lactic acid, xylitol and lignin from lignocellulose raw material.

[0007] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] The present application provides a method for co-production of lactic acid, xylitol and lignin from lignocellulose raw material, which comprises the following steps:

[0009] Step one, pretreating the lignocellulose raw material to obtain pretreated material;

[0010] Step two, performing solid-liquid separation on the pretreated material obtained in step one to obtain a solid phase containing cellulose and lignin, and a liquid phase containing xylitol;

[0011] Step three, fermenting the liquid phase containing xylitol obtained in step two to obtain a fermentation liquor containing xylitol;

[0012] Step four, purifying the fermentation liquor containing xylitol obtained in step three to obtain xylitol.

[0013] Step five, enzymatic hydrolysis of the cellulose and lignin containing solid phase obtained in step two to obtain an enzymatic hydrolysis liquid containing glucose and lignin;

[0014] Step six, solid-liquid separation of the enzymatic hydrolysis liquid containing glucose and lignin obtained in step five to obtain a solid phase containing lignin and a liquid phase containing glucose;

[0015] Step seven, purification of the solid phase containing lignin obtained in step six to obtain lignin;

[0016] Step eight, fermentation of the liquid phase containing glucose obtained in step six to obtain a fermentation liquid containing lactic acid;

[0017] Step nine, purification of the fermentation liquid containing lactic acid obtained in step eight to obtain lactic acid.

[0018] Further, the lignocellulose raw material is one or more of corn stalks, rice stalks, wheat stalks, reeds and bean stalks.

[0019] Further, in step one, the pretreatment is one or more of acid treatment, alkali treatment, ammonia treatment, steam explosion treatment and screw pressure instant puffing treatment; the specific steps of the screw pressure instant puffing treatment are: impregnating the lignocellulose raw material with 1wt% to 4wt% sulfuric acid, and then treating at a temperature of 150°C to 230°C, a pressure of 0.6MPaG to 1.2MPaG, for 20min to 40min.

[0020] Further, in step two, the solid-liquid separation is one or both of plate and frame filtration and centrifugal separation. Centrifugal separation is preferred.

[0021] Further, in step three, the fermentation is carried out using a xylitol fermentation strain, the fermentation inoculation amount is 5% to 20%, the fermentation temperature is 20°C to 40°C, the fermentation pH is pH4 to pH6, and the fermentation time is 24h to 96h.

[0022] Further preferably, the fermentation inoculation amount is 10% to 15%, the fermentation temperature is 30°C to 35°C, the fermentation pH is pH5.2 to pH5.5, and the fermentation time is 48h to 72h.

[0023] Further, in step four, the purification is one or more of activated carbon decolorization, ultrafiltration, ion exchange, evaporation, crystallization, solid-liquid separation and drying.

[0024] Further preferably, in step four, the specific steps of the purification are as follows:

[0025] (1) activated carbon decolorization: activated carbon dosage 30g / L-33g / L, decolorization temperature 28°C-30°C, decolorization pH 2.8-pH 3.2;

[0026] (2) ultrafiltration: molecular weight cut-off 3KD-10KD;

[0027] (3) ion exchange: D202 anion resin and 001x7 cation resin are used, temperature 25-35°C, time 30-35min;

[0028] (4) evaporation: evaporation temperature 70°C-80°C, xylitol concentration reaches 80%-90%;

[0029] (5) crystallization: when the temperature is reduced to 60°C-70°C, seed crystals are added, and crystallization is carried out with stirring, at a rate of 0.5°C-1.5°C per hour to room temperature;

[0030] (6) solid-liquid separation: centrifuge is used;

[0031] (7) drying: dried to a moisture content of 0.5wt%.

[0032] Further, in step five, the enzyme used in the enzymatic hydrolysis is an enzyme produced by Trichoderma reesei and / or Aspergillus niger, and the enzyme dosage is 0.01-0.3g / g cellulose, and the enzyme dosage refers to the total amount of various enzymes; the enzyme hydrolysis dry matter concentration is 10wt%-30wt%, the enzyme hydrolysis pH is 4-6, and the enzyme hydrolysis time is 48h-144h.

[0033] Further preferably, the enzyme hydrolysis dry matter concentration is 15wt%-25wt%, the enzyme hydrolysis pH is 4.5-5.5, and the enzyme hydrolysis time is 72h-96h.

[0034] Further, in step six, the solid-liquid separation is selected from one or both of plate and frame filtration and centrifugal separation. Centrifugal separation is preferred.

[0035] Further, in step seven, the purification is selected from one or more of acid, base, organic solvent, solid-liquid separation, water washing, and drying.

[0036] Further preferably, in step seven, the specific steps of the purification are as follows:

[0037] (1) base dissolution: sodium hydroxide is used to dissolve the lignin-containing solid phase, temperature 20°C-80°C, time 1h-4h, pH 9-pH 13;

[0038] (2) solid-liquid separation: centrifugal separation is used to obtain a solution containing lignin;

[0039] (3) acid precipitation: sulfuric acid is added to precipitate lignin at room temperature, and then centrifugal separation is used to obtain lignin residue;

[0040] (4) water washing: water washing the lignin residue, and then centrifuging to obtain the water washed lignin residue;

[0041] (5) drying: air flow drying the water washed lignin residue to obtain the lignin.

[0042] Further, in step eight, the fermentation is carried out by using lactic acid fermentation bacteria, the fermentation inoculation amount is 5% to 20%, the fermentation temperature is 30℃ to 50℃, the fermentation pH is 5 to 7, and the fermentation time is 24 to 96 hours.

[0043] Further preferably, in step eight, the fermentation inoculation amount is 10% to 15%, the fermentation temperature is 35℃ to 45℃, the fermentation pH is 5.5 to 6.2, and the fermentation time is 48 to 72 hours.

[0044] Further, in step nine, the purification is selected from one or more of solid-liquid separation, acidification, activated carbon decolorization, ultrafiltration, ion exchange, and evaporation.

[0045] Further preferably, in step nine, the specific steps of the purification are as follows:

[0046] (1) solid-liquid separation: scraping centrifuging the fermentation liquid containing lactic acid to obtain lactic acid liquid;

[0047] (2) acidification: then adding sulfuric acid in the lactic acid liquid, and acidifying at 70℃ to 80℃ for 2 to 3 hours;

[0048] (3) solid-liquid separation: adopting plate and frame filtration to obtain acidified liquid;

[0049] (4) activated carbon decolorization: adding 0.5% to 1% activated carbon in the acidified liquid, and decolorizing at 50℃ to 60℃ for 0.5 to 1 hour;

[0050] (5) ultrafiltration;

[0051] (6) cation exchange and anion exchange;

[0052] (7) evaporation: adopting evaporation to concentrate the lactic acid concentration to 80% to 90%;

[0053] (8) distillation: adopting molecular distillation, the pressure is 100Pa to 150Pa, and the temperature is 60℃ to 70℃, to obtain lactic acid product.

[0054] Compared with the prior art, the present application has the following advantages:

[0055] The present application uses lignocellulose as raw material to co-produce lactic acid, xylitol and lignin, which is beneficial to guarantee food safety, realize green and low-carbon development, solve the environmental problems caused by straw burning, increase the income of farmers, and has good social and environmental benefits. DETAILED DESCRIPTION

[0056] The present application will be described in detail and specifically through specific examples, so that the present application can be better understood. However, the following examples do not limit the scope of the present application.

[0057] Example 1

[0058] The present embodiment provides a method for co-producing lactic acid, xylitol and lignin from lignocellulose raw material, which comprises the following steps:

[0059] Step one, the lignocellulose raw material is pretreated by screw pressure instant expansion process, the lignocellulose raw material is impregnated with 1wt% sulfuric acid, then treated at a temperature of 230℃, a pressure of 1.2MPaG for 40min, to obtain pretreated material.

[0060] Step two, the pretreated material obtained in step one is subjected to solid-liquid separation (using centrifugal separation) to obtain a solid phase containing cellulose and lignin, and a liquid phase containing xylose.

[0061] Step three, the liquid phase containing xylose obtained in step two is subjected to fermentation with xylitol fermentation strain, the fermentation inoculation amount is 10%, the fermentation temperature is 35℃, the fermentation pH is 5.2-5.5, and the fermentation time is 72h, to obtain a fermentation liquor containing xylitol.

[0062] Step four, the fermentation liquor containing xylitol obtained in step three is purified to obtain xylitol;

[0063] The specific steps of the above purification are as follows:

[0064] (1) activated carbon decolorization: activated carbon dosage 30g / L, decolorization temperature 30℃, decolorization pH 2.8-3.2;

[0065] (2) ultrafiltration: molecular weight cut-off 3KD-10KD;

[0066] (3) ion exchange: D202 negative resin and 001x7 positive resin are used, temperature 25-35℃, time 30-35min;

[0067] (4) evaporation: evaporation temperature 70-80℃, xylitol concentration reaches 80-90%;

[0068] (5) crystallization: when the temperature drops to 60℃, seed crystals are added, and crystallization is carried out by stirring, with a decrease of 1.5℃ per hour to room temperature;

[0069] (6) solid-liquid separation: centrifuge;

[0070] (7) drying: drying to a moisture content of 0.5 wt%.

[0071] Step five, enzymatic hydrolysis of the cellulose and lignin-containing solid phase obtained in step two using enzymes produced by Trichoderma reesei and / or Aspergillus niger, the enzyme dosage (referring to the total amount of various enzymes) being 0.01 g / g cellulose, the enzyme hydrolysis dry matter concentration being 15 wt%, the enzyme hydrolysis pH being 4.5-5.5, and the enzyme hydrolysis time being 96 h, to obtain a glucose and lignin-containing enzyme hydrolysate.

[0072] Step six, solid-liquid separation (centrifugal separation) of the glucose and lignin-containing enzyme hydrolysate obtained in step five to obtain a lignin-containing solid phase and a glucose-containing liquid phase.

[0073] Step seven, purification of the lignin-containing solid phase obtained in step six to obtain lignin;

[0074] The specific steps of the above purification are as follows:

[0075] (1) alkali dissolution: dissolving the lignin-containing solid phase using sodium hydroxide, the temperature being 20-80°C, the time being 1-4 h, and the pH being 9-13;

[0076] (2) solid-liquid separation: centrifugal separation to obtain a lignin-containing solution;

[0077] (3) acid precipitation: adding sulfuric acid at room temperature to precipitate the lignin, and then centrifugal separation to obtain a lignin residue;

[0078] (4) water washing: water washing of the lignin residue, and then centrifugal separation to obtain a water-washed lignin residue;

[0079] (5) drying: air flow drying of the water-washed lignin residue to obtain lignin.

[0080] Step eight, fermentation of the glucose-containing liquid phase obtained in step six using a lactic acid fermentation strain, the fermentation inoculation amount being 10%, the fermentation temperature being 45°C, the fermentation pH being 5.5-6.2, and the fermentation time being 72 h, to obtain a lactic acid-containing fermentation broth.

[0081] Step nine, purification of the lactic acid-containing fermentation broth obtained in step eight to obtain lactic acid;

[0082] The specific steps of the above purification are as follows:

[0083] (1) solid-liquid separation: doctor centrifugation of the lactic acid-containing fermentation broth to obtain a lactic acid liquid;

[0084] (2) acidification: adding sulfuric acid to the lactic acid liquid and acidifying at 70°C for 3 h;

[0085] (3) solid-liquid separation: plate and frame filtration to obtain acidified liquid;

[0086] (4) activated carbon decolorization: 0.5% activated carbon is added to the acidified liquid, and decolorization is performed at 60°C for 1 h;

[0087] (5) ultrafiltration;

[0088] (6) cation exchange and anion exchange;

[0089] (7) evaporation: evaporation is used to concentrate the lactic acid concentration to 80% to 90%;

[0090] (8) distillation: molecular distillation is used, with a pressure of 100 Pa to 150 Pa and a temperature of 60°C to 70°C, to obtain a lactic acid product.

[0091] As a preferred example, the above lignocellulosic raw material is one or more of corn stalks, rice stalks, wheat stalks, reeds, and bean stalks.

[0092] Example 2

[0093] This example provides a method for co-producing lactic acid, xylitol, and lignin from a lignocellulosic raw material, including the following steps:

[0094] Step one: the lignocellulosic raw material is pretreated using a screw pressure instant puffing process, the lignocellulosic raw material is impregnated with 4 wt% sulfuric acid, and then treated at a temperature of 150°C, a pressure of 0.6 MPaG, and for 20 min to obtain pretreated material.

[0095] Step two: the pretreated material obtained in step one is subjected to solid-liquid separation (using centrifugal separation) to obtain a solid phase containing cellulose and lignin, and a liquid phase containing xylose.

[0096] Step three: the liquid phase containing xylose obtained in step two is subjected to fermentation using a xylitol fermentation strain, with a fermentation inoculation amount of 15%, a fermentation temperature of 35°C, a fermentation pH of 5.2 to 5.5, and a fermentation time of 72 h to obtain a fermentation liquid containing xylitol.

[0097] Step four: the fermentation liquid containing xylitol obtained in step three is purified to obtain xylitol;

[0098] The specific steps of the above purification are as follows:

[0099] (1) activated carbon decolorization: activated carbon dosage is 33 g / L, decolorization temperature is 28°C, and decolorization pH is 2.8 to 3.2;

[0100] (2) ultrafiltration: molecular weight cutoff is 3 KD to 10 KD;

[0101] (3) Ion exchange: D202 anion resin and 001 x 7 cation resin are used, temperature 25-35°C, time 30-35 min;

[0102] (4) Evaporation: evaporation temperature 70-80°C, xylitol concentration reaches 80-90%;

[0103] (5) Crystallization: when the temperature drops to 70°C, seed crystals are added, and crystallization is stirred at a rate of 0.5°C per hour to room temperature;

[0104] (6) Solid-liquid separation: a centrifuge is used;

[0105] (7) Drying: dried to a moisture content of 0.5 wt%.

[0106] Step five, the solid phase containing cellulose and lignin obtained in step two is subjected to enzymatic hydrolysis using enzymes produced by Trichoderma reesei and / or Aspergillus niger, the amount of enzymes (referring to the total amount of various enzymes) is 0.3 g / g cellulose, the dry matter concentration of enzymatic hydrolysis is 25 wt%, the pH of enzymatic hydrolysis is 4.5-5.5, and the enzymatic hydrolysis time is 72 h, to obtain an enzymatic hydrolysis liquid containing glucose and lignin.

[0107] Step six, the enzymatic hydrolysis liquid containing glucose and lignin obtained in step five is subjected to solid-liquid separation (centrifugal separation) to obtain a solid phase containing lignin and a liquid phase containing glucose.

[0108] Step seven, the solid phase containing lignin obtained in step six is purified to obtain lignin;

[0109] The specific steps of the above purification are as follows:

[0110] (1) Alkaline dissolution: the solid phase containing lignin is dissolved using sodium hydroxide, temperature 20-80°C, time 1-4 h, pH 9-13;

[0111] (2) Solid-liquid separation: centrifugal separation is used to obtain a solution containing lignin;

[0112] (3) Acid precipitation: sulfuric acid is added to precipitate lignin at room temperature, and then centrifugal separation is used to obtain lignin residue;

[0113] (4) Water washing: the lignin residue is washed with water, and then centrifugal separation is used to obtain water-washed lignin residue;

[0114] (5) Drying: the water-washed lignin residue is subjected to air flow drying to obtain lignin.

[0115] Step eight, the liquid phase containing glucose obtained in step six is subjected to fermentation using lactic acid fermentation bacteria, the fermentation inoculation amount is 15%, the fermentation temperature is 35°C, the fermentation pH is 5.5-6.2, and the fermentation time is 48 hours, to obtain a fermentation liquid containing lactic acid.

[0116] Step nine, purifying the lactic acid containing fermentation broth obtained in step eight to obtain lactic acid;

[0117] The specific steps of the above purification are as follows:

[0118] (1) solid-liquid separation: scraping centrifugation is performed on the lactic acid containing fermentation broth to obtain lactic acid liquid;

[0119] (2) acidification: sulfuric acid is then added to the lactic acid liquid, and acidification is performed at 80°C for 2h;

[0120] (3) solid-liquid separation: plate and frame filtration is performed to obtain acidified liquid;

[0121] (4) activated carbon decolorization: 1% activated carbon is added to the acidified liquid, and decolorization is performed at 50°C for 0.5h;

[0122] (5) ultrafiltration;

[0123] (6) cation exchange and anion exchange;

[0124] (7) evaporation: evaporation is performed to concentrate the lactic acid concentration to 80%-90%;

[0125] (8) distillation: molecular distillation is performed at a pressure of 100Pa-150Pa and a temperature of 60°C-70°C to obtain lactic acid product.

[0126] As a preferred example, the above lignocellulose raw material is one or several of corn stalks, rice stalks, wheat stalks, reeds and bean stalks.

[0127] Example 3

[0128] The present example provides a method for co-production of lactic acid, xylitol and lignin from lignocellulose raw material, comprising the following steps:

[0129] Step one, pretreatment of the lignocellulose raw material by screw extrusion instant puffing process, impregnation of the lignocellulose raw material with 3wt% sulfuric acid, then treatment at a temperature of 200°C, a pressure of 0.9MPaG for 30min to obtain pretreated material.

[0130] Step two, solid-liquid separation (centrifugal separation) of the pretreated material obtained in step one to obtain solid phase containing cellulose and lignin, and liquid phase containing xylose.

[0131] Step three, fermentation of the liquid phase containing xylose obtained in step two by xylitol fermentation strain, fermentation inoculation amount 12%, fermentation temperature 32°C, fermentation pH 5.2-pH 5.5, fermentation time 60h to obtain fermentation broth containing xylitol.

[0132] Step four, purifying the xylitol-containing fermentation broth obtained in step three to obtain xylitol;

[0133] The specific steps of the above purification are as follows:

[0134] (1) Activated carbon decolorization: activated carbon dosage 32 g / L, decolorization temperature 29°C, decolorization pH 2.8-pH 3.2;

[0135] (2) Ultrafiltration: molecular weight cut-off 3KD-10KD;

[0136] (3) Ion exchange: D202 anion resin and 001x7 cation resin are used, temperature 25-35°C, time 30-35 min;

[0137] (4) Evaporation: evaporation temperature 70°C-80°C, xylitol concentration reaches 80%-90%;

[0138] (5) Crystallization: when the temperature drops to 65°C, seed crystals are added, and crystallization is carried out with stirring, at a rate of 1.0°C per hour to room temperature;

[0139] (6) Solid-liquid separation: centrifuge is used;

[0140] (7) Drying: dried to a moisture content of 0.5wt%.

[0141] Step five, enzymatic hydrolysis of the cellulose and lignin-containing solid phase obtained in step two using enzymes produced by Trichoderma reesei and / or Aspergillus niger, enzyme dosage (referring to the total amount of various enzymes) 0.2 g / g cellulose, enzyme hydrolysis dry matter concentration 20wt%, enzyme hydrolysis pH 4.5-5.5, enzyme hydrolysis time 84 h, to obtain a glucose and lignin-containing enzyme hydrolysate.

[0142] Step six, solid-liquid separation (centrifugal separation) of the glucose and lignin-containing enzyme hydrolysate obtained in step five to obtain a lignin-containing solid phase and a glucose-containing liquid phase.

[0143] Step seven, purifying the lignin-containing solid phase obtained in step six to obtain lignin;

[0144] The specific steps of the above purification are as follows:

[0145] (1) Alkaline dissolution: the lignin-containing solid phase is dissolved using sodium hydroxide, temperature 20°C-80°C, time 1h-4h, pH 9-pH 13;

[0146] (2) Solid-liquid separation: centrifugal separation is used to obtain a lignin-containing solution;

[0147] (3) Acid precipitation: sulfuric acid is added to precipitate lignin at room temperature, and then centrifugal separation is used to obtain lignin residue;

[0148] (4) water washing: water washing is performed on the lignin residue, and then centrifugal separation is performed to obtain water-washed lignin residue;

[0149] (5) drying: air flow drying is performed on the water-washed lignin residue to obtain lignin.

[0150] Step eight, lactic acid fermentation bacteria are used to ferment the glucose-containing liquid phase obtained in step six, the fermentation inoculation amount is 12%, the fermentation temperature is 40°C, the fermentation pH is 5.5 to 6.2, and the fermentation time is 60 hours, and a fermentation liquid containing lactic acid is obtained.

[0151] Step nine, the fermentation liquid containing lactic acid obtained in step eight is purified to obtain lactic acid;

[0152] The specific steps of the above purification are as follows:

[0153] (1) solid-liquid separation: scraper centrifugation is performed on the fermentation liquid containing lactic acid to obtain a lactic acid liquid;

[0154] (2) acidification: sulfuric acid is then added to the lactic acid liquid, and acidification is performed at 70°C to 80°C for 2 to 3 hours;

[0155] (3) solid-liquid separation: plate and frame filtration is used to obtain an acidified liquid;

[0156] (4) activated carbon decolorization: 0.5% to 1% activated carbon is added to the acidified liquid, and decolorization is performed at 50°C to 60°C for 0.5 to 1 hour;

[0157] (5) ultrafiltration;

[0158] (6) cation exchange and anion exchange;

[0159] (7) evaporation: evaporation is used to concentrate the lactic acid concentration to 80% to 90%;

[0160] (8) distillation: molecular distillation is used, the pressure is 100 Pa to 150 Pa, and the temperature is 60°C to 70°C, to obtain a lactic acid product.

[0161] As a preferred example, the above lignocellulose raw material is one or more of corn straw, rice straw, wheat straw, reed, and bean straw.

[0162] The above only describes the preferred embodiments of the present application, and does not limit the implementation and protection scope of the present application. Those skilled in the art should be able to realize that any equivalent replacement and obvious changes made according to the content of the present application should be included in the protection scope of the present application.

Claims

1. A method for the co-production of lactic acid, xylitol and lignin from a lignocellulosic feedstock, characterized in that, It comprises the following steps: Step one, the lignocellulose raw material is pretreated by screw pressure instant puffing process to obtain pretreated material; the specific steps of the screw pressure instant puffing process are as follows: the lignocellulose raw material is impregnated with 1wt%-4wt% sulfuric acid, and then treated at a temperature of 150°C-230°C and a pressure of 0.6MPaG-1.2MPaG for 20min-40min; Step two, the pretreated material obtained in step one is subjected to solid-liquid separation by centrifugal separation to obtain a solid phase containing cellulose and lignin, and a liquid phase containing xylose; Step three, the liquid phase containing xylose obtained in step two is subjected to fermentation to obtain a fermentation liquor containing xylitol; the fermentation is carried out by using xylitol fermentation strains; Step four, the fermentation liquor containing xylitol obtained in step three is subjected to purification to obtain xylitol; the specific steps of the purification are as follows: activated carbon decolorization, ultrafiltration, ion exchange, evaporation, crystallization, solid-liquid separation and drying; Step five, the solid phase containing cellulose and lignin obtained in step two is subjected to enzymatic hydrolysis to obtain an enzymatic hydrolysis liquor containing glucose and lignin; the enzyme used in the enzymatic hydrolysis is the enzyme produced by Trichoderma reesei and / or Aspergillus niger, and the enzyme dosage is 0.01-0.3g / g cellulose; Step six, the enzymatic hydrolysis liquor containing glucose and lignin obtained in step five is subjected to solid-liquid separation to obtain a solid phase containing lignin, and a liquid phase containing glucose; Step seven, the solid phase containing lignin obtained in step six is subjected to purification to obtain lignin; the specific steps of the purification are as follows: alkali dissolution, solid-liquid separation, acid precipitation, water washing and drying; Step eight, the liquid phase containing glucose obtained in step six is subjected to fermentation to obtain a fermentation liquor containing lactic acid; the fermentation is carried out by using lactic acid fermentation strains; Step nine, the fermentation liquor containing lactic acid obtained in step eight is subjected to purification to obtain lactic acid; the specific steps of the purification are as follows: solid-liquid separation, acidification, obtaining acidified liquid by plate and frame filtration, activated carbon decolorization, ultrafiltration, cation exchange and anion exchange, evaporation and distillation.

2. The method of co-production of lactic acid, xylitol and lignin from lignocellulosic feedstock according to claim 1, characterized in that, The lignocellulose raw material is one or more of corn stalks, rice stalks, wheat stalks, reeds and bean stalks.

3. The method of claim 1, wherein the lignocellulosic feedstock is co-produced with lactic acid, xylitol and lignin. In step three, the fermentation inoculation amount is 5%-20%, the fermentation temperature is 20°C-40°C, the fermentation pH is 4-6, and the fermentation time is 24h-96h.

4. The method of claim 1, wherein the lignocellulosic feedstock is corn stover. In step eight, the fermentation inoculation amount is 5%-20%, the fermentation temperature is 30°C-50°C, the fermentation pH is 5-7, and the fermentation time is 24-96 hours.