CN117487191A

CN117487191A - Method for treating solid residues in biomass fermentation

Info

Publication number: CN117487191A
Application number: CN202210884509.1A
Authority: CN
Inventors: 郜洪兵; 范鹤鸣; 杨晨; 刘修才
Original assignee: Cathay R&D Center Co Ltd; CIBT America Inc
Current assignee: Cathay R&D Center Co Ltd; CIBT America Inc
Priority date: 2022-07-25
Filing date: 2022-07-25
Publication date: 2024-02-02

Abstract

The invention discloses a method for treating solid residues in biomass fermentation. The treatment method comprises the steps of sequentially carrying out 1 st-stage hydrolysis, 2 nd-stage hydrolysis … and N-stage hydrolysis on the solid residue, wherein N is an integer more than or equal to 3; performing solid-liquid separation after the 1 st-stage hydrolysis is performed to obtain 1-stage hydrolysis solid residues and 1-stage hydrolysis filtrate; the 1 st stage hydrolysis adopts 1 st stage acid solution; the 2 nd-stage hydrolysis is carried out to hydrolyze the 1 st-stage hydrolysis solid slag to obtain 2-stage hydrolysis solid slag and 2-stage hydrolysis filtrate; the 2 nd stage hydrolysis adopts a 2 nd stage acid solution; the Nth hydrolysis is carried out to hydrolyze N-1-level hydrolysis solid slag, and N-level hydrolysis solid slag and N-level hydrolysis filtrate are obtained; the N-stage hydrolysis adopts an N-stage acid solution. The invention has excellent separation effect, can obtain high-purity lignin, has high hydrolysis efficiency of cellulose and hemicellulose, can be used as back-end fermentation for the filtrate after hydrolysis, does not involve the problem of acid recovery, improves the added value of components and reduces the acid loss.

Description

Method for treating solid residues in biomass fermentation

Technical Field

The invention relates to comprehensive utilization of solid residues in biomass fermentation, in particular to a method for treating the solid residues in biomass fermentation.

Background

Biomass refers to various organisms produced by photosynthesis using the atmosphere, water, land, etc., that is, all living organic substances that can grow are known as biomass. For example, the agricultural and forestry production process includes straw, tree and other lignocellulose, agricultural product processing leftovers, agricultural and forestry waste, animal manure, waste and other matters. In recent years, comprehensive utilization and recycling of biomass have attracted widespread attention. This opens up a new direction for alleviating environmental problems caused by fossil fuels such as petroleum, coal mine, etc. Compared with the non-degradability of fossil-based materials, the biomass has the advantages of wide sources, short cycle period and good biodegradability.

Taking agricultural straw as an example, the main components of the agricultural straw are cellulose (25% -40%), hemicellulose (20% -35%), lignin (10% -25%), ash (1% -10%), solubles (5% -15%) and others (1% -5%). Cellulose is formed into linear macromolecules by connecting B-D-units through 1-4-glycosidic bonds; hemicellulose is a generic term for non-cellulosic polysaccharides in the cell wall, consisting of two or more glycosyl groups, usually with branched structures; lignin is an aromatic compound with a three-dimensional space structure, which is formed by connecting 3 phenylpropane units through ether bonds and carbon-carbon bonds. Among them, cellulose and hemicellulose are generally converted into 5-carbon or 6-carbon sugar by fermentation or hydrolysis, and further converted into chemical raw materials. The hydrolysis method generally consumes a large amount of inorganic acid or alkali, has higher cost and has larger environmental hazard. The fermentation method is relatively simple to operate, mild in environment and low in comprehensive production cost, and the structure of the residual lignin in the fermentation residues is relatively complete, so that good assurance is provided for lignin application.

After fermentation of biomass, most of the cellulose and hemicellulose are converted into sugar, but the remaining solid residue still contains some cellulose, hemicellulose, a large amount of lignin and ash components. At present, the fermented solid slag is only used as fuel, and the added value of the fermented solid slag is very low. The traditional lignin purifying method is to destroy the macromolecular structure of lignin by using alkali and to dissolve the macromolecular structure in alkali liquor (or directly precipitate lignin by using papermaking black liquor), and then to add acid to adjust pH to 1-3 to precipitate lignin. The dilute acid hydrolysis mode disclosed in the prior art can be utilized to hydrolyze part of cellulose and hemicellulose into sugar, but the sugar conversion rate is lower, and the loss of acid is larger, so that a process for efficiently recycling the cellulose and the hemicellulose in the solid residue is sought, the utilization rate of acid is improved, the ineffective loss of acid (usually utilizing alkali to neutralize the acid, the cost is high and the environmental pollution is aggravated) is reduced, and the method has important significance for optimizing the fermentation process and improving the utilization rate of active ingredients in the straw.

Methods for separating cellulose, hemicellulose and lignin are also disclosed in the prior art, but not for solid residues after fermentation of biomass, but for biomass treatment in many cases. In fact, it is relatively easier to directly separate cellulose, hemicellulose and lignin from biomass. This is mainly because biomass has a relatively high cellulose and hemicellulose content, a low lignin content, and easy separation before fermentation. However, for the residual solid residue after fermentation, the content of cellulose and hemicellulose in the residual solid residue is greatly reduced, the lignin proportion is greatly increased, and the residual cellulose and hemicellulose which are not easy to hydrolyze are tightly combined with lignin, so that the hydrolysis and separation difficulty is obviously increased. Therefore, how to treat the solid residue after biomass fermentation, efficiently separate lignin and improve the utilization rate of cellulose and hemicellulose is a technical problem which is not solved at present.

Disclosure of Invention

The invention mainly aims to overcome the defect that the solid residues after biomass fermentation cannot be efficiently utilized in the prior art, and the cost of obtaining lignin with higher purity is higher by the existing separation method, and provides a method for treating the solid residues in biomass fermentation. By adopting the treatment method, the solid residues after biomass fermentation can be well separated, the separation effect is excellent, the lignin with high purity can be obtained, the hydrolysis efficiency of cellulose and hemicellulose is also at a higher level, and meanwhile, the filtrate after hydrolysis can be used as the back-end fermentation, so that the problem of acid recovery is avoided, the additional value of components is greatly improved, and the acid loss is reduced.

The invention mainly solves the technical problems through the following technical scheme.

The invention provides a method for treating solid residues in biomass fermentation, which comprises the following steps: sequentially carrying out level 1 hydrolysis, level 2 hydrolysis … and level N hydrolysis on the solid residues, wherein N is an integer more than or equal to 3;

after the 1 st-stage hydrolysis is carried out to hydrolyze the solid residues, carrying out solid-liquid separation to obtain 1-stage hydrolysis solid residues and 1-stage hydrolysis filtrate; the 1 st stage hydrolysis is carried out by adopting a 1 st stage acid solution;

the 2 nd-stage hydrolysis is carried out after the 1 st-stage hydrolysis solid slag is hydrolyzed, and 2 nd-stage hydrolysis solid slag and 2 nd-stage hydrolysis filtrate are obtained through solid-liquid separation; the 2 nd-stage hydrolysis is carried out by adopting a 2 nd-stage acid solution;

after the Nth-stage hydrolysis is carried out to hydrolyze N-1-stage hydrolysis solid residues, carrying out solid-liquid separation to obtain N-stage hydrolysis solid residues and N-stage hydrolysis filtrate; the Nth stage hydrolysis is performed by adopting an N-stage acid solution.

The inventor of the invention discovers that the solid residue obtained by biomass fermentation has higher lignin content, and the residual cellulose and hemicellulose which are not easy to hydrolyze are tightly combined with lignin, so that the hydrolysis of cellulose and hemicellulose is more difficult to occur, and the difficulty of separating the cellulose and hemicellulose from lignin is obviously increased. However, the solid residue is subjected to hydrolysis reaction continuously for three times or more by adopting an acid solution with a specific concentration at a certain solid-to-liquid ratio and a hydrolysis temperature, so that lignin with high purity can be obtained, and the hydrolysis rate of cellulose and hemicellulose is also at a high level.

Further, the researchers found that the use of the hydrolyzed filtrate as an acid solution to hydrolyze the solid residue three or more times can achieve a comparable separation effect as compared to the hydrolysis performed the same number of times with a newly prepared acid solution. This can fully demonstrate that the filtrate after hydrolysis can continue to hydrolyze the solid residues after fermentation, and the hydrolysis filtrate is not required to be subjected to wastewater treatment, so that the maximum utilization of the hydrolysis filtrate is realized. Preferably, the hydrolysis filtrate is introduced into the upper stage 1 hydrolysis in a countercurrent manner for hydrolysis.

In the development process, the applicant found that the hydrolysis rate is not improved significantly after the time reaches a certain level by only prolonging the hydrolysis time in the same system. Even if the system after the 1 st-stage hydrolysis is subjected to solid-liquid separation, the solid-liquid separation is continuously carried out on the obtained hydrolyzed solid residues by recycling the hydrolyzed filtrate, so that the improvement degree is limited. The inventor finds that the purity of the obtained lignin, the hydrolysis rate of cellulose and hemicellulose are all obviously improved by adopting a countercurrent mode of acid hydrolysis filtrate to carry out multistage hydrolysis.

In the present invention, the 1-stage acid solution is preferably the 2-stage hydrolysis filtrate.

In the present invention, the 2-stage acid solution is preferably a 3-stage hydrolysis filtrate.

In the present invention, the N-1 stage acid solution is preferably an N stage hydrolysis filtrate. The N-2-level acid solution is the N-1-level hydrolysis filtrate, and the like, and the hydrolysis filtrate of the later 1-level is used as the acid solution of the first 1-level in a step-by-step countercurrent mode.

In the invention, the N-level acid solution is preferably an acid solution prepared at present, so that the countercurrent recycling of the hydrolysis filtrate is realized. Wherein the now formulated acid solution refers to an acid solution that has not undergone hydrolysis reaction, and the now formulated is not a time limitation.

In the present invention, when n=4, the treatment method preferably further includes a 4 th stage hydrolysis and a 4 th stage acid solution is used for hydrolysis reaction, and the 4 th stage hydrolysis solid residue and 4 stage hydrolysis filtrate are obtained by solid-liquid separation after the 4 th stage hydrolysis. The grade 3 acid solution is preferably the grade 4 hydrolysis filtrate, in which case the grade 4 acid solution is the now formulated acid solution.

In the invention, the N-level hydrolysis solid slag is lignin obtained by separation.

The 1-level hydrolysis filtrate enters a fermentation end of fermenting the monosaccharide into lactic acid and is continuously used, the 1-level hydrolysis filtrate contains cellulose and hemicellulose, and the monosaccharide obtained by decomposing the cellulose and the hemicellulose in the hydrolysis reaction enters the fermentation end to be hydrolyzed and fermented until a fermentation end product is obtained.

By adopting the mode of countercurrent hydrolysis filtrate, biomass fermentation solid residues sequentially pass through the 1 st-stage hydrolysis, the 2 nd-stage hydrolysis … … and the N-stage hydrolysis to fully hydrolyze to obtain high-purity lignin, and the hydrolysis rate of cellulose and hemicellulose is also at a very high level, and meanwhile, the hydrolysis filtrate in each stage of hydrolysis returns to the upper 1-stage hydrolysis to continue to hydrolyze, so that the maximum utilization of the hydrolysis filtrate is realized.

In the invention, the concentration of the 1-stage acid solution is preferably not more than the concentration of the 2-stage acid solution, and is more preferably less than the concentration of the 2-stage acid solution, namely the 2-stage hydrolysis filtrate.

In the present invention, the concentration of the 1-stage acid solution is preferably 1 to 30wt%, more preferably 5 to 15wt%, for example 8wt%, 10wt%, 11wt%, 12wt%, 13wt% or 20wt%, wt% means the ratio of the mass of the acid to the total mass of the acid solution.

In the present invention, the acid species in the 1-stage acid solution is preferably one or more of sulfuric acid, phosphoric acid, hydrochloric acid and acetic acid, more preferably sulfuric acid.

In the present invention, in the stage 1 hydrolysis, the mass ratio of the solid residue to the stage 1 acid solution may be 1 (1 to 20), further 1 (1 to 15), still further 1 (1 to 10), for example 1:5, 1:10, 1:13 or 1:18.

In the present invention, in the stage 1 hydrolysis, the temperature of the hydrolysis reaction is preferably 80 to 200 ℃, further 100 to 180 ℃, further 120 to 160 ℃, for example 130 ℃, 140 ℃ or 150 ℃.

In the present invention, in the stage 1 hydrolysis, the time for the hydrolysis reaction may be 1 to 8 hours, further 1 to 6 hours, further 1 to 5 hours, for example 2 hours or 4 hours.

In the present invention, in the stage 1 hydrolysis, the pressure of the hydrolysis reaction may be 0 to 2MPa, preferably 0.2 to 1.2MPa.

In the invention, the concentration of the 2-stage acid solution is preferably not more than the concentration of the 3-stage acid solution, and is more preferably less than the concentration of the 3-stage acid solution, namely the 3-stage hydrolysis filtrate.

In the present invention, the concentration of the 2-stage acid solution is preferably 1 to 30wt%, more preferably 5 to 15wt%, for example 8wt%, 10wt%, 11wt%, 12wt%, 13wt% or 20wt%, wt% means the ratio of the mass of the acid to the total mass of the acid solution.

In the present invention, the acid species in the 2-stage acid solution is preferably one or more of sulfuric acid, phosphoric acid, hydrochloric acid and acetic acid, more preferably sulfuric acid.

In the present invention, in the level 2 hydrolysis, the mass ratio of the level 1 hydrolysis solid residue to the level 2 acid solution may be 1 (1-20), further 1 (1-15), further 1 (1-10), for example, 1:5, 1:10, 1:13 or 1:18.

In the present invention, in the stage 2 hydrolysis, the temperature of the hydrolysis reaction is preferably 80 to 200 ℃, further 100 to 180 ℃, further 120 to 160 ℃, for example 130 ℃, 140 ℃ or 150 ℃.

In the present invention, in the stage 2 hydrolysis, the time for the hydrolysis reaction may be 1 to 8 hours, further 1 to 6 hours, further 1 to 5 hours, for example 2 hours or 4 hours.

In the present invention, in the 2 nd stage hydrolysis, the pressure of the hydrolysis reaction may be 0 to 2MPa, preferably 0.2 to 1.2MPa.

In the present invention, the concentration of the N-1 stage acid solution is preferably equal to or less than the concentration of the N-stage acid solution, more preferably less than the concentration of the N-stage acid solution.

In the present invention, the concentration of the N-stage acid solution is preferably 1 to 30wt%, more preferably 5 to 15wt%, for example 8wt%, 10wt%, 11wt%, 12wt%, 13wt% or 20wt%, wt% means the ratio of the mass of the acid to the total mass of the acid solution.

In the present invention, the acid species in the N-stage acid solution is preferably one or more of sulfuric acid, phosphoric acid, hydrochloric acid and acetic acid, more preferably sulfuric acid.

In the present invention, in the nth stage hydrolysis, the mass ratio of the N-1 stage hydrolysis solid residue to the N-stage acid solution may be 1 (1 to 20), further 1 (1 to 15), and further 1 (1 to 10), for example, 1:5, 1:10, 1:13, or 1:18.

In the present invention, in the Nth stage hydrolysis, the temperature of the hydrolysis reaction is preferably 80 to 200 ℃, further 100 to 180 ℃, further 120 to 160 ℃, for example 130 ℃, 140 ℃ or 150 ℃.

In the present invention, in the nth stage hydrolysis, the time of the hydrolysis reaction may be 1 to 8 hours, further 1 to 6 hours, further 1 to 5 hours, for example 2 hours or 4 hours.

In the present invention, in the nth stage hydrolysis, the pressure of the hydrolysis reaction may be 0 to 2MPa, preferably 0.2 to 1.2MPa.

In the present invention, the 1 st stage hydrolysis, the 2 nd stage hydrolysis … … and the nth stage hydrolysis are performed in a vessel of a pressure-resistant metal reaction vessel or a pressure-resistant glass vessel.

In the present invention, the solvent in the 1-stage acid solution, the 2-stage acid solution … … and the N-stage acid solution is generally water.

In the invention, the solid-liquid separation can be conventional in the art, for example, hydrolysis solid slag and hydrolysis filtrate are obtained by separation through filtration. The main component of the hydrolysis solid slag is lignin, and the main component of the hydrolysis filtrate comprises cellulose and hydrolysis products thereof, hemicellulose and hydrolysis products thereof.

In the invention, in each 1-stage hydrolysis, the main components of the hydrolysis filtrate are glucose, xylose, arabinose, pigment, protein, metal ions, acid and water, wherein the acid refers to the acid in the 1-stage acid solution, the 2-stage acid solution or the 3-stage acid solution.

In the invention, in each 1-level hydrolysis, the main component of the hydrolysis solid slag is lignin, but also comprises a small amount of cellulose, hemicellulose, acid, sugar and water.

In the present invention, step (3) preferably further comprises washing the N-stage hydrolysis solid residue.

Wherein the washed solvent is typically water. Such washing means include, but are not limited to, rinsing and/or pickling. In order to improve the availability, the washing liquid after washing is preferably combined with the 1-grade hydrolysis filtrate, and the washing liquid can dissolve residual sugar compounds when the adopted washing solvent is water, so that the washing liquid is used as back-end fermentation for continuous use, the bioavailability is improved, and meanwhile, the washing liquid is basically free of lignin or has little residue but does not influence further fermentation.

Wherein the number of times of washing is preferably three.

Wherein the washing is preferably washing the insoluble matter to a pH of 6.5 to 7.5.

Wherein the washing is further followed by a drying operation to remove residual moisture, and the drying may be freeze drying, atmospheric drying, reduced pressure drying or spray drying.

In the invention, N-level hydrolysis filtrate and water washing liquid generated during washing can be uniformly mixed to form dilute acid aqueous solution containing sugar, and the dilute acid aqueous solution is recycled to a fermentation end for reuse.

In the present invention, the biomass is derived from agricultural and forestry waste, and the biomass may include one or more of straw, rice hull, cork, hardwood, branch and livestock manure, preferably straw. Such as one or more of corn stover, wheat straw, rice straw, canola straw, barley straw, oat straw, and sorghum straw.

In the present invention, the fermentation may be conventional in the art, and in particular, the fermentation of lactic acid using a strain of fermented lactic acid generally comprises the steps of: pretreating and/or detoxication the biomass, and fermenting by adopting a strain for fermenting lactic acid. The strain of fermented lactic acid is preferably Pediococcus acidilactici.

Wherein the pretreatment is a conventional operation, and the biomass is reduced in size by mechanical pulverization after being washed and dried, and then the pretreatment is performed. The pretreatment may include dilute acid, sulfur dioxide, ammonia fiber explosion or steam explosion, preferably dilute acid. The pretreatment preferably means that the biomass is soaked with a dilute sulfuric acid solution and maintained at 180-200 ℃ for 1-10 minutes.

Wherein, the detoxification generally refers to that mold with detoxification capability (such as cladosporium resina, paecilomyces variotii and the like) is inoculated simultaneously or before the pretreatment of the biomass is inoculated with pediococcus acidilactici, so as to remove inhibitors affecting fermentation, such as organic acid formic acid, acetic acid, furan furfural, hydroxymethyl furfural and the like produced by pretreatment. Pretreatment and detoxification facilitate subsequent fermentation.

In the present invention, the conditions of the fermentation are preferably a fermentation temperature of 35 to 50 ℃, and/or a pH of 4.5 to 6.5, a fermentation time of 50 to 100 hours, and/or a mass fraction of biomass in the fermentation broth of 10 to 45%, and/or a cellulase of 1 to 30mg protein/g biomass (dry basis), and/or an inoculum size of the strain at the time of the fermentation of 5 to 15% (v/v).

In the invention, the fermentation can refer to the steps of synchronous saccharification and fermentation after solid biodegradation is carried out on lignocellulose materials in CN112941117A to remove inhibitors. More specifically, for example, the fermentation process disclosed in example 2 is directed to corn stover after pretreatment, final biodegradation to remove inhibitors.

In one embodiment of the invention, the fermentation comprises the steps of: putting 30 (w/w)% of solid content corn straw in solid particle form subjected to dry dilute acid pretreatment and Paecilomyces variotii detoxification as a raw material into a fermentation tank containing a certain amount of water, adding 5mg of protein per gram of corn straw (dry basis) cellulase, and performing pre-saccharification for 6.5 hours at 48 ℃ and 200 rpm; after the pre-saccharification is finished, inoculating the pediococcus acidilactici seed liquid into a fermentation tank according to an inoculation amount of 5% (v/v), adding a nutrient solution, adjusting and maintaining the pH value of the fermentation liquid to be 5.4 by using calcium carbonate as a neutralizer in the fermentation process, fermenting at 42 ℃ for 96 hours at 200rpm, and then separating the fermentation liquid from solid residues by solid-liquid separation to obtain solid residues in biomass fermentation. The nutrient solution may include 10g/L peptone, 10g/L yeast extract, 2g/L diammonium hydrogen citrate, and 0.25g/L manganese sulfate monohydrate. After fermentation, the fermentable monosaccharides in the corn stalks can be converted into lactic acid, and the lactic acid fermentation liquid is subjected to suction filtration, so that the lactic acid fermentation liquid is separated from the biomass solid residues.

In the present invention, the solid residue may be in the meaning conventionally understood in the art, and generally refers to a solid residue separated after fermentation of biomass.

In the present invention, the solid residue generally includes lignin, cellulose and hemicellulose.

Wherein the lignin content is preferably 30 to 80wt%, more preferably 40 to 70wt%, for example 50wt%, 52.14wt%, 55wt% or 60wt%, the wt% being a percentage of the total mass of the solid residue.

Wherein the cellulose content is preferably below 30wt%, more preferably 1-20 wt%, still more preferably 10-20 wt%, for example 15wt%, 16.45wt%, 17wt% or 18wt%, wt% being a percentage of the total mass of the solid residue.

Wherein the hemicellulose content is preferably below 20wt%, more preferably 1-10 wt%, more preferably 1-5 wt%, for example 2wt%, 2.82wt%, 3wt% or 4wt%, the wt% being a percentage of the total mass of the solid residue.

In the present invention, other components, which are generally understood to be materials obtained by fermentation of biomass other than lignin, cellulose and hemicellulose, may be included in the solid residue.

Wherein the content of the other components may comprise 10 to 30wt%, for example 20 to 30wt%.

Wherein the specific species of the other components may include one or more of lactic acid, inorganic salts, metal ions, pigments, proteins, monosaccharides and oligosaccharides. The oligosaccharide may be in the meaning conventionally understood in the art, and generally refers to polymers formed by 2 to 10 glycosidic linkages.

In one embodiment of the invention, the solid residue consists of 15-20wt% of cellulose, 1-5wt% of hemicellulose, 50-70wt% of lignin and other components, wherein the other components are the rest. Wherein the other ingredients may include one or more of lactic acid, protein and inorganic salts.

In one embodiment of the invention, the solid residue consists of 16.45wt% cellulose, 2.82wt% hemicellulose, 52.14wt% lignin and 28.59wt% other components. Wherein the other ingredients may include one or more of lactic acid, protein and inorganic salts.

In the present invention, the fineness of the solid residue is preferably 50 to 200 mesh, more preferably 50 to 150 mesh, for example 100 to 150 mesh. The fineness of the solid residues influences the effect of the hydrolysis reaction, and the fineness in the range can realize better separation efficiency and lower preparation cost by matching with other hydrolysis conditions in the invention.

In the present invention, the fermentation product after fermentation of the biomass may be conventional in the art, for example, lactic acid or ethanol.

On the basis of conforming to the common knowledge in the field, the above preferred conditions can be arbitrarily combined to obtain the preferred examples of the invention.

The reagents and materials used in the present invention are commercially available.

The invention has the positive progress effects that:

(1) According to the treatment method, hydrolysis reaction is carried out on solid residues in biomass fermentation for more than three times, so that the solid residues in biomass are hydrolyzed by using an acid solution, hydrolysis solid residues and hydrolysis filtrate are respectively obtained, wherein the hydrolysis solid residues are high-purity lignin, hydrolysis products of mainly cellulose and hemicellulose, namely monosaccharides, acid (acid in the acid solution) and a small amount of cellulose and hemicellulose in the hydrolysis filtrate can be input into a process of fermenting the monosaccharides into lactic acid to play an important role, wherein the monosaccharides are directly used as fermentation raw materials for products such as lactic acid and the like, the acid plays a catalytic role in biomass fermentation, the decomposition of biomass is promoted, and the use amount of acid in fermentation is greatly reduced. The defect of cost investment in recovery of chemical reagents in the traditional process is effectively avoided, and dependence on combined action of multiple chemical reagents in the component separation process is eliminated.

(2) The treatment method disclosed by the invention has the advantages of lower required temperature, simple operation process and higher sugar conversion rate, can save production cost, reduce energy consumption and improve the added value of biomass solid slag.

(3) The treatment method effectively improves the purity of lignin in the residues while hydrolyzing cellulose and hemicellulose of solid residues in biomass fermentation, provides a new thought for extracting and purifying lignin, has low lignin dissociation degree, greatly maintains the three-dimensional space structure of lignin, and is beneficial to improving the performance of lignin in the material application process.

Drawings

FIG. 1 is a flow chart showing the treatment of the solid residue in example 1 of the present invention.

Detailed Description

The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.

The invention will be described in detail below by way of examples. In the examples below, the various raw materials used are available from commercial sources, unless otherwise specified; the physical parameters related to the raw materials or the performance parameters of the products are measured by the conventional method in the field.

(1) Method for testing solid residue components in biomass fermentation

The method for measuring the content of cellulose and hemicellulose adopts a high performance liquid chromatography, and a chromatographic column adopts Phenomenex RezexTM RPM-Momosaccharide Pb +2 or Biorad Aminex HPX-87P and an equivalent column thereof. Under the action of acid, cellulose and hemicellulose are mainly decomposed into glucose, xylose, arabinose and the like, under the same test method, standard sugar calibration is utilized, the relative content of each sugar can be directly calculated through liquid chromatography, and then the content of the cellulose and the hemicellulose is calculated.

The hydrolysis rates of cellulose and hemicellulose were calculated by using the measured content measurements.

(2) The method for measuring the lignin content in the invention adopts an ultraviolet spectrophotometry and a gravimetric method.

300.0mg of fermentation solid residue or hydrolyzed solid residue is weighed and put into a pressure-resistant test tube, and then 3.00mL of 72% sulfuric acid solution is added into the test tube to be uniformly mixed. Placing the pressure-resistant tube in a water bath shaking table (150 r/min) at 30 ℃, reacting for 60min at constant temperature, taking the pressure-resistant tube out of the water bath shaking table, adding 84.00mL of deionized water, screwing down a bottle cap, reversing the pressure-resistant tube for several times, and uniformly mixing the samples. Placing the pressure-resistant tube and the sugar recovery standard solution which is prepared in advance into a high-temperature high-pressure sterilizing pot, reacting for 1h at 121 ℃, filtering by using a glass sand core crucible with constant weight after the hydrolysis is completed and cooled to room temperature, collecting filtrate by using a conical flask, and flushing acid-insoluble residues remained in the pressure-resistant test tube by using at least 100mL of deionized water to ensure that the residues are all remained in the glass sand core crucible. The collected filtrate is used for measuring the content of cellulose and hemicellulose and measuring acid-soluble lignin, the filter residue in the glass sand core crucible is used for measuring acid-insoluble lignin, and the acid-soluble lignin and the acid-insoluble lignin are added to obtain the lignin content.

In the examples below, the solid residue was obtained by the following fermentation process: putting the pretreated corn stalks in solid particle form with 30 (w/w)% of solid content into a fermentation tank as a raw material, adding 5mg of cellulase/g of stalks (dry weight), and performing pre-saccharification for 6.5 hours at 48 ℃ and 200 rpm; after the pre-saccharification is finished, inoculating the pediococcus acidilactici seed liquid into a fermentation tank according to an inoculation amount of 5% (v/v), adding nutrient solution (10 g/L peptone, 10g/L yeast extract, 2g/L diammonium hydrogen citrate and 0.25g/L manganese sulfate monohydrate) simultaneously, regulating and maintaining the pH value of the fermentation liquid to be 5.4 by using calcium carbonate as a neutralizer in the fermentation process, fermenting at 42 ℃ for 96 hours at 200rpm, and then carrying out solid-liquid separation on the fermentation liquid and solid residues to obtain the solid residues in biomass fermentation.

The components of the solid residues treated in examples 1 to 17 below were examined as follows: 16.45wt% cellulose, 2.82wt% hemicellulose, 52.14wt% lignin and 28.59wt% other components including lactic acid, proteins and inorganic salts.

The solid residues in the biomass fermentation employed in examples 1 to 17 below were: crushing the solid residues obtained after fermenting the dry biomass by using a crusher to obtain powdery crushed residues, wherein the particle size is 100-150 meshes.

A counter-current treatment system for the hydrolysis filtrate was established prior to proceeding with the following examples: the treatment system comprises a 1 st stage hydrolysis tank, a 2 nd stage hydrolysis tank and a 3 rd stage hydrolysis tank which are connected in series;

simultaneously, respectively adding 20g of fermented solid residues into the three hydrolysis tanks, simultaneously adding the acid solution prepared at present for hydrolysis reaction, and after each time of hydrolysis reaction, adding 20g of fermented solid residues into the 1 st-stage hydrolysis tank, and simultaneously adding the acid solution prepared at present with a specific concentration into the 3 rd-stage hydrolysis tank until the following process can be realized, as shown in the following figure 1:

in the level 1 hydrolysis tank, the level 2 hydrolysis filtrate generated in the level 2 hydrolysis tank is adopted to carry out hydrolysis reaction on solid residues after biomass fermentation, level 1 hydrolysis solid residues and level 1 hydrolysis filtrate are generated, the level 1 hydrolysis solid residues enter the level 2 hydrolysis tank, and the level 1 hydrolysis filtrate enters a subsequent fermentation end to be continuously used.

In the 2 nd level hydrolysis tank, 3 level hydrolysis filtrate generated in the 3 rd level hydrolysis tank is adopted to carry out hydrolysis reaction on the 1 st level hydrolysis solid slag, 2 level hydrolysis solid slag and 2 level hydrolysis filtrate are generated, and as mentioned before, the 2 level hydrolysis filtrate enters the 1 st level hydrolysis tank to be reused, and the 2 level hydrolysis solid slag enters the 3 rd level hydrolysis tank to continue hydrolysis reaction.

In the 3 rd level hydrolysis tank, the prepared acid solution is adopted to carry out hydrolysis reaction on the 2 nd level hydrolysis solid slag to generate 3 rd level hydrolysis solid slag and 3 rd level hydrolysis filtrate, and as mentioned before, the 3 rd level hydrolysis filtrate enters the 2 nd level hydrolysis tank to be reused, and the 3 rd level hydrolysis solid slag is washed and dried to obtain the lignin with high purity.

Each 1-stage hydrolysis tank is a pressure-resistant device, and a pressure-resistant stainless steel container is used in the following example.

Example 1

(1) Acidolysis: when the countercurrent treatment system is established in the mode, the acid solution which is prepared at present is a sulfuric acid aqueous solution with the concentration of 12wt%, the solid-to-liquid ratio in each level 1 hydrolysis tank is (w/w) 1:5, the hydrolysis reaction temperature in each hydrolysis tank is 140 ℃, the hydrolysis reaction is carried out in each level 1 hydrolysis tank under stirring, and the hydrolysis reaction time in each level 1 hydrolysis tank is 4 hours.

Continuously adding 20g of biomass fermented solid residues into the level 1 hydrolysis tank until the level 1 hydrolysis tank can be used for carrying out hydrolysis reaction on the biomass fermented solid residues by adopting level 2 hydrolysis filtrate to obtain level 1 hydrolysis solid residues and level 1 hydrolysis filtrate; the 2 nd stage hydrolysis tank hydrolyzes the 1 st stage hydrolysis solid slag by adopting 3 stage hydrolysis filtrate, the 3 rd stage hydrolysis tank hydrolyzes the 2 stage hydrolysis solid slag by adopting the sulfuric acid aqueous solution with the concentration of 12wt% prepared in the prior art, the oil bath is closed after the hydrolysis reaction in the 1 st stage hydrolysis tank is completed, 100mL of water is added to reduce the temperature of the system, and the liquid is filtered to obtain the 3 stage hydrolysis solid slag.

(2) Washing: washing the 3-stage hydrolysis solid slag by deionized water, filtering, collecting filtrate, and mixing with the 1-stage hydrolysis filtrate to obtain mixed hydrolysis liquid and lignin crude product. The hydrolysis efficiencies of cellulose and hemicellulose in the characterization mixed hydrolysate are respectively as follows: 90.32%,98.98%.

(3) And (3) recycling: and (3) recycling the mixed hydrolysate obtained in the step (2) to a fermentation end for repeated use, and providing a direct sugar source for fermentation.

(4) And (3) drying: placing the lignin crude product in the step (2) in a freeze dryer, and removing water to obtain the lignin crude product, wherein the quality of the lignin crude product is as follows: 11.27g, the lignin is characterized by a purity of 88.73%.

Example 2

In this example, the solid-to-liquid ratio (w/w) in each stage 1 hydrolysis tank was 1:10, and the hydrolysis reaction was carried out in the same manner as in example 1 by countercurrent flow of the hydrolysis filtrate.

The hydrolysis efficiencies of cellulose and hemicellulose in the mixed hydrolysis filtrate after washing are respectively represented as follows: 90.51%,87.73%. The quality of the lignin crude product after freeze drying is as follows: 11.58g, characterizing lignin purity as 89.81%.

Example 3

In this example, the solid-to-liquid ratio (w/w) in each stage 1 hydrolysis tank was 1:13, and the hydrolysis reaction was carried out in the same manner as in example 1 by countercurrent flow of the hydrolysis filtrate.

The hydrolysis efficiencies of cellulose and hemicellulose in the mixed hydrolysis filtrate after washing are respectively represented as follows: 93.15%,99.32%. The quality of the lignin crude product after freeze drying is as follows: 10.73g, characterizing lignin purity as 91.23%.

Example 4

In this example, the solid-to-liquid ratio (w/w) in each stage 1 hydrolysis tank was 1:18, and the hydrolysis reaction was carried out in the same manner as in example 1 by countercurrent flow of the hydrolysis filtrate.

The hydrolysis efficiencies of cellulose and hemicellulose in the mixed hydrolysis filtrate after washing are respectively represented as follows: 99.23%,99.93%. The quality of the lignin crude product after freeze drying is as follows: 11.32g, characterizing lignin purity 88.05%.

Example 5

In this example, the temperature of the oil bath in each stage 1 hydrolysis tank was 150℃and the hydrolysis reaction was carried out in the same manner as in example 2 by countercurrent flow of the hydrolysis filtrate.

The hydrolysis efficiencies of cellulose and hemicellulose in the mixed hydrolysis filtrate after washing are respectively represented as follows: 97.15%,72.32%. The quality of the lignin crude product after freeze drying is as follows: 11.22g, characterizing lignin purity as 88.52%.

Example 6

In this example, the temperature of the oil bath in each stage 1 hydrolysis tank was 160℃and the hydrolysis reaction was carried out in the same manner as in example 2 by countercurrent flow of the hydrolysis filtrate.

The hydrolysis efficiencies of cellulose and hemicellulose in the mixed hydrolysis filtrate after washing are respectively represented as follows: 45.37%,87.13%. The quality of the lignin crude product after freeze drying is as follows: 13.17g, characterizing lignin purity as 73.93%.

Example 7

In this example, the temperature of the oil bath in each stage 1 hydrolysis tank was 130℃and the hydrolysis reaction time in each stage 1 hydrolysis tank was 2 hours, and the hydrolysis reaction was carried out by countercurrent flow of the hydrolysis filtrate in the same manner as in example 2.

The hydrolysis efficiencies of cellulose and hemicellulose in the mixed hydrolysis filtrate after washing are respectively represented as follows: 67.54%,89.89%. The quality of the lignin crude product after freeze drying is as follows: 12.97g, characterizing lignin purity as 74.35%.

Example 8

In this example, the temperature of the oil bath in each stage 1 hydrolysis tank was 120℃and the hydrolysis reaction time in each stage 1 hydrolysis tank was 6 hours, and the hydrolysis reaction was carried out in the same manner as in example 2 by countercurrent flow of the hydrolysis filtrate.

The hydrolysis efficiencies of cellulose and hemicellulose in the mixed hydrolysis filtrate after washing are respectively represented as follows: 87.32%,87.17%. The quality of the lignin crude product after freeze drying is as follows: 11.87g, characterizing lignin purity 79.87%.

Example 9

In this example, the temperature of the oil bath in each stage 1 hydrolysis tank was 120℃and the hydrolysis reaction time in each stage 1 hydrolysis tank was 8 hours, and the hydrolysis reaction was carried out in the same manner as in example 2 by using a countercurrent flow of the hydrolysis filtrate.

The hydrolysis efficiencies of cellulose and hemicellulose in the mixed hydrolysis filtrate after washing are respectively represented as follows: 76.39%,89.17%. The quality of the lignin crude product after freeze drying is as follows: 12.14g, characterizing lignin purity 78.15%.

Example 10

In this example, the concentration of the aqueous sulfuric acid solution prepared at present was 4wt%, the temperature of the oil bath in each hydrolysis tank was 150℃and the hydrolysis reaction was carried out in the same manner as in example 2 by countercurrent flow of the hydrolysis filtrate.

The hydrolysis efficiencies of cellulose and hemicellulose in the mixed hydrolysis filtrate after washing are respectively represented as follows: 83.12%,85.72%. The quality of the lignin crude product after freeze drying is as follows: 12.15g, characterizing lignin purity as 75.35%.

Example 11

In this example, the concentration of the aqueous sulfuric acid solution prepared at present was 8wt%, the temperature of the oil bath in each hydrolysis tank was 180℃and the hydrolysis reaction was carried out in the same manner as in example 2 by countercurrent flow of the hydrolysis filtrate.

The hydrolysis efficiencies of cellulose and hemicellulose in the mixed hydrolysis filtrate after washing are respectively represented as follows: 87.97%,63.15%. The quality of the lignin crude product after freeze drying is as follows: 11.94g, characterizing lignin purity 80.23%.

Example 12

In this example, the concentration of the aqueous sulfuric acid solution prepared at present was 10wt%, and the hydrolysis reaction was carried out in the same manner as in example 2 by countercurrent flow of the hydrolysis filtrate.

The hydrolysis efficiencies of cellulose and hemicellulose in the mixed hydrolysis filtrate after washing are respectively represented as follows: 89.86%,67.13%. The quality of the lignin crude product after freeze drying is as follows: 11.53g, characterizing lignin purity 88.88%.

Example 13

In this example, the concentration of the aqueous sulfuric acid solution prepared at present was 20wt%, the temperature of the oil bath in each hydrolysis tank was 130 ℃, and the hydrolysis reaction was carried out in the same manner as in example 2 by countercurrent flow of the hydrolysis filtrate.

The hydrolysis efficiencies of cellulose and hemicellulose in the mixed hydrolysis filtrate after washing are respectively represented as follows: 96.71%,66.43%. The quality of the lignin crude product after freeze drying is as follows: 10.97g, characterizing lignin purity as 89.93%.

Example 14

The concentration of the acid solution prepared in this example was the same as in example 2, and the addition of acid to the stage 1 and stage 2 hydrolysis tanks was such that the concentration of the aqueous sulfuric acid solution in the hydrolysis filtrate was consistent with the concentration of the aqueous sulfuric acid solution prepared.

The hydrolysis efficiencies of cellulose and hemicellulose in the mixed hydrolysis filtrate after washing are respectively represented as follows: 93.52%,89.32%. The quality of the lignin crude product after freeze drying is as follows: 10.88g, characterizing lignin purity as 92.85%.

Example 15

In this example, only the 1 st stage hydrolysis tank and the 2 nd stage hydrolysis tank are included, the 2 nd stage hydrolysis filtrate generated in the 2 nd stage hydrolysis tank is adopted in the 1 st stage hydrolysis tank to hydrolyze, the acid solution prepared at present is adopted in the 2 nd stage hydrolysis tank to hydrolyze, and the other parameters and steps are set as in example 2.

The hydrolysis efficiencies of cellulose and hemicellulose in the mixed hydrolysis filtrate after washing are respectively represented as follows: 78.25%,68.06%. The quality of the lignin crude product after freeze drying is as follows: 12.22g, characterizing lignin purity of 83.91%.

Example 16

The acid solution used in this example was hydrochloric acid, the solid-to-liquid ratio in each 1-stage hydrolysis tank was (w/w) 1:10, and the other was hydrolyzed by countercurrent flow of the hydrolysis filtrate as in example 1.

The hydrolysis efficiencies of cellulose and hemicellulose in the mixed hydrolysis filtrate after washing are respectively represented as follows: 89.73%,87.19%. The quality of the lignin crude product after freeze drying is as follows: 10.32g, characterizing lignin purity 87.85%.

Example 17

The hydrolysis is carried out once by adopting the acid solution prepared at present to obtain hydrolysis solid slag and hydrolysis filtrate, the 1-level hydrolysis solid slag is washed to test the purity of lignin, meanwhile, the washing solution is mixed with the hydrolysis filtrate to test the hydrolysis rate of cellulose and hemicellulose, and the test results are shown in the following table 1, and the parameters of the hydrolysis reaction are the same as in example 2.

In table 1, the solid-to-liquid ratio, the acid type, the hydrolysis temperature, and the hydrolysis time in examples 1 to 17 refer to parameters in each stage of hydrolysis reaction in each example, and the acid concentration refers to the concentration of the acid solution prepared in each example.

TABLE 1

According to the experimental results obtained by the measurement, the solid residues in biomass fermentation are treated by adopting the specific acid solution to carry out hydrolysis reaction at a specific temperature and a solid-liquid ratio for a certain time, and the solid residues in the same batch are continuously subjected to three hydrolysis reactions, so that lignin with purity of more than 70% is obtained, and meanwhile, the hydrolysis rates of cellulose and hemicellulose are also at a higher level.

Further, the invention skillfully flows the hydrolysis filtrate in the reverse direction, simultaneously flows the solid residues to be hydrolyzed in the forward direction, and hydrolyzes the hydrolysis solid residues of the upper 1 level by adopting the hydrolysis filtrate of the later 1 level, thereby not only fully utilizing the acid solution, but also obtaining lignin with higher purity and higher hydrolysis rate of cellulose and hemicellulose. The final hydrolysis filtrate in the treatment process is used as the back-end fermentation to be used continuously, and the problem of acid recovery is avoided. The high-purity lignin obtained in the embodiment of the invention has the advantages that the sulphonatable groups are increased when the lignin is used as a water reducing agent, the water reducing effect is better, the cellulose and hemicellulose achieve higher hydrolysis rate, the content of the five-carbon sugar and the six-carbon sugar which can be used in the back-end fermentation is higher, and the yield of lactic acid products obtained by fermentation is also obviously improved.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.

Claims

1. A method for treating solid residues in biomass fermentation, which is characterized by comprising the following steps: sequentially carrying out level 1 hydrolysis, level 2 hydrolysis … and level N hydrolysis on the solid residues, wherein N is an integer more than or equal to 3;

2. The method for treating solid residues in biomass fermentation according to claim 1, wherein the 1-stage acid solution is the 2-stage hydrolysis filtrate;

and/or, the 2-stage acid solution is 3-stage hydrolysis filtrate;

and/or, the N-1 stage acid solution is the N stage hydrolysis filtrate;

and/or the N-stage acid solution is an acid solution prepared at present;

and/or the concentration of the 1-stage acid solution is less than or equal to the concentration of the 2-stage acid solution, preferably less than the concentration of the 2-stage acid solution;

and/or the concentration of the 2-stage acid solution is less than or equal to the concentration of the 3-stage acid solution, preferably less than the concentration of the 3-stage acid solution;

and/or the concentration of the N-1 stage acid solution is less than or equal to the concentration of the N-stage acid solution, and is preferably less than the concentration of the N-stage acid solution.

3. A method of treating solid residues in the fermentation of biomass as claimed in claim 2, wherein the concentration of the 1-stage acid solution is 1 to 30wt%, preferably 5 to 15wt%;

and/or the acid in the 1-stage acid solution is one or more of sulfuric acid, phosphoric acid, hydrochloric acid and acetic acid;

and/or, in the stage 1 hydrolysis, the mass ratio of the solid residue to the stage 1 acid solution is 1 (1-20), preferably 1 (1-15), more preferably 1 (1-10);

and/or, in the stage 1 hydrolysis, the temperature of the hydrolysis reaction is 80-200 ℃, preferably 100-180 ℃, more preferably 120-160 ℃;

and/or, in the stage 1 hydrolysis, the time of the hydrolysis reaction is 1 to 8 hours, preferably 1 to 6 hours, and more preferably 1 to 5 hours.

4. A method of treating solid residues in the fermentation of biomass as claimed in claim 2, wherein the concentration of the 2-stage acid solution is 1 to 30wt%, preferably 5 to 15wt%;

and/or the type of acid in the 2-stage acid solution is one or more of sulfuric acid, phosphoric acid, hydrochloric acid and acetic acid;

and/or, in the 2 nd stage hydrolysis, the mass ratio of the 1 st stage hydrolysis solid slag to the 2 nd stage acid solution is 1 (1-20), preferably 1 (1-15), and more preferably 1 (1-10);

and/or, in the 2 nd stage hydrolysis, the temperature of the hydrolysis reaction is 80-200 ℃, preferably 100-180 ℃, more preferably 120-160 ℃;

and/or, in the 2 nd stage hydrolysis, the time of the hydrolysis reaction is 1 to 8 hours, preferably 1 to 6 hours, and more preferably 1 to 5 hours.

5. The method for treating solid residues in the fermentation of biomass as claimed in claim 2, wherein the concentration of the N-stage acid solution is 1 to 30% by weight, preferably 5 to 15% by weight;

and/or the acid in the N-level acid solution is one or more of sulfuric acid, phosphoric acid, hydrochloric acid and acetic acid;

and/or, in the Nth hydrolysis, the mass ratio of the N-1 hydrolysis solid slag to the N-stage acid solution is 1 (1-20), preferably 1 (1-15), and more preferably 1 (1-10);

and/or, in the Nth stage hydrolysis, the temperature of the hydrolysis reaction is 80-200 ℃, preferably 100-180 ℃, more preferably 120-160 ℃;

and/or, in the Nth stage hydrolysis, the hydrolysis reaction time is 1 to 8 hours, preferably 1 to 6 hours, and more preferably 1 to 5 hours.

6. The method for treating a solid residue in biomass fermentation according to any one of claims 1 to 5, wherein step (3) further comprises washing the N-stage hydrolysis solid residue;

wherein the washed solvent is preferably water;

wherein, the washing is preferably to wash the N-level hydrolysis solid slag to a pH value of 6.5-7.5;

wherein said washing is preferably followed by drying.

7. The method of treating a solid residue in biomass fermentation according to any one of claims 1 to 5, wherein the biomass comprises one or more of straw, rice hulls, cork, hardwood, branches, and livestock manure;

wherein the straw preferably comprises one or more of corn straw, wheat straw, rice straw, canola straw, barley straw, oat straw and sorghum straw.

8. The method for treating a solid residue in biomass fermentation according to claim 7, wherein the solid residue comprises lignin, cellulose and hemicellulose;

and/or the fineness of the solid residue is 50 to 200 mesh, preferably 50 to 150 mesh, more preferably 100 to 150 mesh;

and/or, the fermentation comprises the steps of: pretreating and/or detoxication the biomass, and fermenting by adopting a strain for fermenting lactic acid;

wherein the strain of fermented lactic acid is for example Pediococcus acidilactici;

wherein, the fermentation condition is preferably that the fermentation temperature is 35-50 ℃, and/or the pH is 4.5-6.5, the fermentation time is 50-100 hours, and/or the mass fraction of biomass in the fermentation liquor is 10-45%, and/or the cellulase is 1-30 mg protein/g biomass, and/or the inoculation amount of the strain during fermentation is 5-15%.

9. The method for treating a solid residue in biomass fermentation according to claim 8, wherein the lignin content is 30 to 80wt%, and wt% is a percentage of the total mass of the solid residue;

and/or the content of the cellulose is below 30wt%, and the wt% is the percentage of the total mass of the solid residue;

and/or the hemicellulose content is below 20wt%, and the wt% is the percentage of the total mass of the solid residue.

10. The method for treating a solid residue in biomass fermentation according to claim 9, wherein the lignin content is 40 to 70wt%;

and/or the cellulose content is 1 to 20wt%, preferably 10 to 20wt%;

and/or the hemicellulose content is 1 to 10wt%, preferably 1 to 5wt%.