Method for co-production of organic acids, xylose and lignin from lignocellulose

Abstract

The application provides a method for co-producing organic acid, xylose and lignin from lignocellulose, which comprises the following steps: step one, component separation is performed on lignocellulose raw materials to obtain cellulose, xylose and lignin, wherein the method for component separation is alkali dissolution and acid precipitation and / or solvent treatment; and step two, acid production fermentation is performed on the cellulose in step one to obtain an organic acid mixture. The method provided by the application can efficiently separate xylose and lignin, and the step of producing acid is simple and controllable, and the effect of producing acid is good.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bio-chemical production, further relates to a method for co-producing organic acid, xylose and lignin from lignocellulose. BACKGROUND

[0002] In order to realize the sustainable development of resources and alleviate the problem of the continuous consumption of non-renewable resources, people are constantly seeking to develop biomass resources to replace non-renewable resources. Green plants are the first choice for the development of biomass resources because of their fast growth, renewability and large base.

[0003] Lignocellulose is mainly composed of hemicellulose, lignin and cellulose. Hemicellulose is a short branched heteropolysaccharide and is used to produce xylitol. Lignin is a cross-linked phenolic polymer and can be oxidized and polycondensed, and is used as an additive for epoxy resin, rubber and thermoplastic plastic, and is an important high molecular material. Cellulose is a polymer of monosaccharide glucose covalently linked by beta-1,4 bond, and is an important raw material for pulp and papermaking, textiles and chemical fibers. Lignocellulose widely exists in the stems, leaves and pericarps of plants. There are many materials containing lignocellulose that can be used, such as agricultural crop residues, waste paper, herbaceous plants and wood. Therefore, it is of great significance to separate hemicellulose, lignin and cellulose from the above renewable biomass resources and utilize them in a high-value way.

[0004] Lignocellulose is abundant and renewable. In recent years, people have also used lignocellulose as a raw material to prepare various organic acids. For example, patent CN114032257A provides a method for co-producing lactic acid, xylitol and lignin from lignocellulose raw materials. After pretreatment of the lignocellulose raw material, a liquid phase containing xylose and a solid phase containing cellulose and lignin are obtained by solid-liquid separation. The solid phase containing cellulose and lignin is subjected to enzymatic hydrolysis to obtain a liquid phase containing glucose. The liquid phase containing glucose is subjected to fermentation and purification to obtain lactic acid. Patent CN109715816A provides a method for producing organic acid from lignocellulose raw materials. Alkali liquor from a pulp mill is pretreated to obtain a cellulose feed. The cellulose feed is subjected to enzymatic hydrolysis to obtain a sugar feed. The sugar feed is subjected to microbial fermentation to obtain an organic acid. It is worth mentioning that in this invention, the cellulose can be first subjected to enzymatic hydrolysis and then subjected to fermentation to obtain an organic acid, or the enzymatic hydrolysis and fermentation processes can be carried out simultaneously, but the parameters such as raw material, enzyme, microorganism and concentration need to be reasonably adjusted. The above two methods both need to add enzymes to convert cellulose into glucose before fermentation to produce acid. The steps are complicated and the reaction system is difficult to control, which is not suitable for industrial production. SUMMARY

[0005] To solve the above problems, the application provides a method for co-producing organic acid, xylose and lignin from lignocellulose, which can efficiently separate xylose and lignin, and has simple and controllable acid production steps and good acid production effect.

[0006] The application aims to provide a method for co-producing organic acid, xylose and lignin from lignocellulose, which comprises the following steps:

[0007] Step one: component separation of lignocellulose raw materials to obtain cellulose, xylose and lignin, wherein the component separation adopts alkali dissolution and acid precipitation;

[0008] Step two: acid production fermentation of the cellulose obtained in step one to obtain an organic acid mixture.

[0009] Further, in step one, the alkali dissolution and acid precipitation method comprises the following steps:

[0010] (1) pretreatment of the lignocellulose raw materials by using one or a combination of pulverization and impurity removal, acid treatment, alkali treatment and steam explosion treatment to obtain pretreated materials;

[0011] (2) water washing and solid-liquid separation of the pretreated materials to obtain a liquid phase containing xylose and a solid phase containing cellulose and lignin;

[0012] (3) alkali treatment of the solid phase containing cellulose and lignin, solid-liquid separation to obtain a liquid phase containing lignin and a solid phase containing cellulose;

[0013] (4) water washing and solid separation of the solid phase containing cellulose to obtain cellulose wet materials and water washing liquid containing lignin;

[0014] (5) combination of the liquid phase containing lignin in step (3) and the water washing liquid containing lignin in step (4), acid treatment, heating treatment and solid-liquid separation to obtain lignin wet materials, and drying of the lignin to obtain lignin.

[0015] Preferably, the lignocellulose in the application is from one or a combination of corn stalks, rice stalks, wheat stalks, reeds, corn cobs or bean stalks.

[0016] Preferably, in step (1), the pulverization and impurity removal adopts a complete set of pulverization and impurity removal equipment, which comprises coarse pulverization, impurity and iron removal, fine pulverization and dust removal sections.

[0017] Further, in step two, the conditions for acid production fermentation are as follows:

[0018] The batch fermentation, semi-continuous fermentation or continuous fermentation is carried out under anaerobic conditions; the pH of the acid-producing fermentation is 5-10; preferably, the pH is 5-7; the temperature of the acid-producing fermentation is 32-58 DEG C; preferably, the temperature is 35-53 DEG C; the C / N ratio is 20-60; preferably, the C / N ratio is 30-40; the solid content is 2.5-15%; preferably, the solid content is 2.5-12%; and the fermentation time is 2-50 days; preferably, the fermentation time is 7-21 days.

[0019] Preferably, the nitrogen source is one or a combination of NH4Cl, corn slurry, sludge, potassium nitrate and urea.

[0020] Preferably, the acid-producing fermentation of the present application uses an acid-producing microbial flora; preferably, the acid-producing microbial flora is enriched by the method provided in the patent application (application number 2023113103664).

[0021] Specifically, the enrichment method of the acid-producing microbial flora in anaerobic fermentation includes F1 stage-F3 stage, that is, the reactor can be divided into F1, F2 and F3 stages during the whole operation process, and the organic load of straw is gradually increased in the three stages until the stable operation in the F3 stage. Among them, the F1 stage is the reactor starting stage, and the solid content and the load are low. The solid content and the load are increased to enter the F2 stage, the C / N ratio is increased by increasing the straw proportion in the material after the F2 acid production is stable, and the F3 stage is entered, so that the microbial flora adapts to the high C / N ratio straw material.

[0022] Specifically as follows:

[0023] F1 stage:

[0024] The operation time of the F1 stage is 80-120 days, and preferably 100-110 days;

[0025] The inoculum is added to the reactor, nitrogen is introduced to discharge air, and then the reactor is closed; no material is fed into or out of the reactor for two days after starting the reactor, and then the substrate is supplied under the condition of 0.4-0.6 g VTS / L / d organic load; wherein the TS value of the substrate is 4.8-5.4%; the VTS value is 4.0-4.4%; the C / N ratio is 18-22; the material can be fed into or out of the reactor every two days, the hydraulic retention time of the reactor is 90-110 days; and the physicochemical parameters of the reactor can be monitored every four days.

[0026] Specifically, regarding the inoculum:

[0027] The solid content of the inoculum used in the present application is ≤5%.

[0028] Further, in order to inhibit the activity of methanogens, the inoculum source is preferably pretreated by heat treatment at 75-85℃ for 0.5-1.2 hours and addition of a methane inhibitor at a final concentration of 4-6 mM. Preferably, the methane inhibitor is 2-bromoethanosulfophate (BES).

[0029] Further, the inoculum source can comprise inocula of different origins; in particular, the inocula of different origins can be selected from a mixture of food sugar factory anaerobic digestion sludge, kitchen waste anaerobic digestion sludge, cellulose anaerobic digestion sludge, glucose anaerobic digestion sludge, and fruit waste anaerobic fermentation acid production reactor sludge. The cellulose anaerobic digestion sludge is preferably cellulose high-temperature anaerobic digestion sludge or cellulose mesophilic anaerobic digestion sludge; the glucose anaerobic digestion sludge is preferably glucose high-temperature anaerobic digestion sludge or glucose mesophilic anaerobic digestion sludge. The type of sludge can be selected according to the different reaction temperatures.

[0030] Further, the inoculum source comprises inocula of different origins mixed according to the total solids (TS) content, each sludge accounting for more than 10% of the total solids (TS) content, and more preferably, the inocula of different origins are mixed in equal proportions according to the total solids (TS) content.

[0031] In particular, the inoculum source can be crushed with a blender and then filtered (for example, filtered with 2-3 layers of gauze) to ensure that the solid content of the sludge used to start the reactor is below 5%.

[0032] In particular, regarding the substrate:

[0033] The substrate used in the present application is a mixture comprising straw, kitchen waste, and nitrogen source substrate; in the F1 stage, the VTS ratio of straw, kitchen waste, and nitrogen source substrate in the substrate is preferably (0.8-1.2):(0.8-1.2):(0.8-1.2).

[0034] Further, the source substrate can be a substrate commonly used in the art, and in particular, sewage plant residual sludge can be used; a large amount of residual sludge is produced during the treatment of sewage using the activated sludge method in sewage treatment plants in China, and the sludge treatment process is not yet mature. Using sewage plant residual sludge as the nitrogen source substrate can recycle the sludge, is environmentally friendly, and saves costs.

[0035] Further, the straw can be selected from at least one or a combination of corn straw, rice straw, wheat straw, reed, or bean straw.

[0036] Further, the straw can be steam exploded straw, which can be steam exploded straw treated by conventional steam explosion in the art, or can be prepared by the following method: adding straw material and water into a closed container, maintaining for a period of time (which can be several minutes), and then suddenly reducing the pressure to steam explode the straw material, so as to destroy the hemicellulose and lignin connection layer, expose more active groups of cellulose, and be more conducive to degradation.

[0037] Further, the kitchen waste can be conventional kitchen waste, or can be self-made, for example, by mixing fruits, vegetables, and grain powder after being crushed.

[0038] Preferably, the substrate can be stored at low temperature (for example, 4℃), and is diluted to the target solid content when used.

[0039] Specifically, as to the reactor:

[0040] The reactor used in the present application can be a high-temperature reactor or a medium-temperature reactor. A conventional reactor in the art can be selected, for example, a conventional mechanical stirring tank and the like. The stirring speed of the reactor can be 0-150 ppm, so as to mix the materials uniformly.

[0041] Preferably, the pH value of the reactor is 5.5-6.0; the working temperature of the high-temperature reactor is 50-55℃; and the working temperature of the medium-temperature reactor is 35-40℃.

[0042] Further, when the reactor is a high-temperature reactor, the cellulose anaerobic digestion sludge can be selected from cellulose high-temperature anaerobic digestion sludge, and the glucose anaerobic digestion sludge can be selected from glucose high-temperature anaerobic digestion sludge.

[0043] Further, when the reactor is a medium-temperature reactor, the cellulose anaerobic digestion sludge can be selected from cellulose medium-temperature anaerobic digestion sludge, and the glucose anaerobic digestion sludge can be selected from glucose medium-temperature anaerobic digestion sludge.

[0044] In specific practice, a semi-continuous complete-mixed-flow anaerobic fermentation acid production reactor system can be constructed, and a high-temperature reactor or a medium-temperature reactor can be used to enrich high-temperature bacterial flora and medium-temperature bacterial flora, respectively.

[0045] F2 stage:

[0046] The running time of the F2 stage is 50-100 days, preferably 75-90 days; the pH value of the reactor is 5.5-6.0; the feed solid content is adjusted to 8-12%, the organic load is increased to 0.8-1.2 g VTS / L / d, the substrate TS is 9.8-10.5%, the substrate VTS is 8.0-8.5%, the VTS ratio of straw, kitchen waste and sludge in the substrate is (0.8-1.2):(0.8-1.2):(0.8-1.2), the substrate C / N ratio is 18-22, the reactor can be fed and discharged once every two days, the hydraulic retention time of the reactor can be 90-110 days, and the running is continued until stabilization.

[0047] The F3 stage:

[0048] The running time of the F3 stage is 120-200 days, preferably 165-185 days; the pH value of the reactor is 5.5-6.0; the feed solid content is kept unchanged (the feed solid content in this stage is 8-12%), the organic load is increased to 1.8-2.2 g VTS / L / d, the hydraulic retention time is adjusted to 45-55 days, the VTS ratio of straw, kitchen waste and sludge in the feed is changed from (0.8-1.2):(0.8-1.2):(0.8-1.2) to (2.8-3.2):(1.8-2.2):(0.8-1.2), the substrate C / N ratio is increased from 18-22 to 38-42, the substrate TS is 9.5-10%, the substrate VTS is 8.0-8.6%, the reactor can be fed and discharged once every two days, the running is continued until stabilization, and the microbial flora in the reactor during the stable running of the F3 stage is collected.

[0049] It is worth mentioning that the microbial flora in the reactor during the stable running of the F3 stage is collected, and the specific method is as follows: the fermentation liquor is centrifuged at 4°C for 10 minutes, the supernatant is removed, and the precipitated part is the microbial flora. The enriched microbial flora is used for the acid production fermentation of cellulose.

[0050] Preferably, after the acid production fermentation of cellulose, a fermentation liquor containing a mixed organic acid is obtained, wherein the organic acid in the fermentation liquor is a plurality of combinations of lactic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid and isovaleric acid.

[0051] Compared with the prior art, the present application has the following beneficial effects: the present application provides a process for co-production of mixed organic acid, xylose and lignin by using lignocellulose as raw material to replace grain raw material, the composition and content of the acid in the mixed organic acid can be adjusted by controlling the acid production fermentation conditions, and the lignocellulose does not need to be enzymatically hydrolyzed after pretreatment, so the cost is low. BRIEF DESCRIPTION OF DRAWINGS

[0052] Figure 1 The flow chart of the present application for co-production of organic acid, xylose and lignin by using lignocellulose as raw material. DETAILED DESCRIPTION

[0053] It is necessary to point out that the following examples are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Some non-essential improvements and adjustments to the present application made by a person skilled in the art according to the content of the present application still fall within the scope of protection of the present application.

[0054] The raw materials used in the examples, if not particularly limited, are disclosed in the prior art, for example, can be directly purchased or prepared according to the preparation method disclosed in the prior art.

[0055] The sources of sludge, kitchen waste and straw used in the examples of the present application are as follows:

[0056] Anaerobic digestion sludge of grain sugar factory: COFCO biochemical (Chengdu) Co., Ltd.;

[0057] Anaerobic digestion sludge of kitchen waste: the stable operation anaerobic methane production reactor of the Environmental Biotechnology Research Center of the School of Architecture and Environment of Sichuan University, the kitchen waste is taken from the student cafeteria of Sichuan University;

[0058] Cellulose high-temperature anaerobic digestion sludge: the stable operation high-temperature anaerobic methane production reactor of the Environmental Biotechnology Research Center of the School of Architecture and Environment of Sichuan University, with commercially available carboxymethyl cellulose as carbon source;

[0059] Cellulose mesophilic anaerobic digestion sludge: the stable operation mesophilic anaerobic methane production reactor of the Environmental Biotechnology Research Center of the School of Architecture and Environment of Sichuan University, with commercially available carboxymethyl cellulose as carbon source;

[0060] Glucose high-temperature anaerobic digestion sludge: the stable operation high-temperature anaerobic methane production reactor of the Environmental Biotechnology Research Center of the School of Architecture and Environment of Sichuan University, with commercially available glucose as carbon source;

[0061] Glucose mesophilic anaerobic digestion sludge: the stable operation mesophilic anaerobic methane production reactor of the Environmental Biotechnology Research Center of the School of Architecture and Environment of Sichuan University, with commercially available glucose as carbon source;

[0062] Fruit waste anaerobic fermentation acid production reactor sludge: the stable operation anaerobic fermentation acid production reactor of the Environmental Biotechnology Research Center of the School of Architecture and Environment of Sichuan University, with commercially available fruits (banana, watermelon, orange mixed in a weight ratio of 1:1:1) as raw material;

[0063] The excess sludge of sewage plant is the dewatered sludge of a certain municipal sewage treatment plant in Chengdu;

[0064] The artificial preparation of kitchen waste is a mixture of banana, orange, Chinese cabbage and rice powder after crushing and wet weight mixing.

[0065] Steam-exploded straw is steam-exploded straw, wherein the steam explosion treatment comprises adding corn straw and water in a closed container, maintaining a pressure of 1.7 MPa for 2 minutes, and then suddenly reducing the pressure to perform steam explosion on the straw material.

[0066] Table 1 shows the TS and VTS data of inocula and substrates from different sources.

[0067] Table 1

[0068]

[0069] In the examples, one high-temperature reactor (working volume 4 L) and one medium-temperature reactor (working volume 2.4 L) were prepared respectively to enrich bacteria suitable for high temperature and bacteria suitable for medium temperature respectively.

[0070] Example 1

[0071] This example is used to illustrate the enrichment method of microbial flora.

[0072] 1. Reactor construction

[0073] Preparation of inoculum: In order to enrich anaerobic fermentation acid-producing microbial community, anaerobic digestion sludge from grain sugar factory, anaerobic digestion sludge from kitchen waste, cellulose high-temperature anaerobic digestion sludge, glucose high-temperature anaerobic digestion sludge and fruit waste anaerobic fermentation acid-producing reactor sludge were mixed as inoculum; different source inocula were mixed in equal proportion (i.e. 1:1:1:1:1) according to total solids (TS) (the TS and VTS of different source inocula are shown in Table 1).

[0074] Preparation of substrate: steam-exploded straw, artificially prepared kitchen waste (banana, orange, Chinese cabbage and rice powder were crushed and mixed in equal wet weight), and residual sludge from sewage plant were used as substrate, and different substrates were mixed in equal proportion according to volatile total solids (VTS) (the TS and VTS of various substrates are shown in Table 1). The mixed substrate was stored at 4°C, and was diluted to the target solid content when used.

[0075] One high-temperature reactor (working volume 4 L, named H) was prepared.

[0076] 2. Reactor start-up and operation

[0077] The present application starts one high-temperature reactor (H).

[0078] The whole running process of the reactor is divided into F1, F2 and F3 stages, and the organic load of straw is gradually increased in the three stages until stable operation in the F3 stage. The operating conditions of the reactor in the three stages are shown in Table 2.

[0079] Day 0-105 is F1 stage,

[0080] The high-temperature reactor is started and run at 53℃, the stirring speed is 100 rpm, and the pH value is controlled at 5.5-6.0. The inoculum from various sources is mixed in equal proportions according to TS, broken by a blender, and filtered with 2-3 layers of gauze to ensure that the solid content of the starting sludge in the reactor is below 5%. In order to inhibit the activity of methanogens, the starting sludge needs to be pretreated. The starting sludge is heat-treated at 80℃ for 1 hour, and 5mM of the methanogenesis inhibitor 2-bromoethanosulfophate (BES) is added. The pretreated mixed inoculum is injected into the working volume of the reactor, nitrogen is introduced to remove air to reach an anaerobic state, and then the reactor is closed. After starting the reactor, no material is fed for two days, and then under the condition of 0.5g VTS / L / d organic load, substrates containing straw, kitchen waste and sludge (TS: 5.2%; VTS: 4.1%; C / N ratio: 20) are supplied, the VTS ratio of straw, kitchen waste and sludge in the substrate is 1:1:1, the material is fed in and out every two days, and the hydraulic retention time of the reactor is 100 days. The physicochemical parameters of the reactor are monitored every four days.

[0081] Day 105-189 is F2 stage,

[0082] The hydraulic retention time is maintained at 100 days in this stage, the solid content of the feed is adjusted to 10%, the TS of the substrate is 10.3%, the VTS of the substrate is 8.2%, the VTS ratio of straw, kitchen waste and sludge in the substrate is 1:1:1, the C / N ratio of the substrate is 20, the organic load is increased to 1g VTS / L / d, and the operation is continued until stable.

[0083] Day 189-368 is F3 stage,

[0084] The solid content of the feed is maintained at 10% in this stage, the organic load is increased to 2g VTS / L / d, the hydraulic retention time is adjusted to 50 days, the TS of the substrate is 9.7%, the VTS of the substrate is 8.3%, and the VTS ratio of straw, kitchen waste and sludge in the feed is changed from 1:1:1 to 3:2:1, the proportion of straw is increased and the proportion of sludge is reduced, and the C / N ratio of the feed is increased from 20 to 40. The operation is continued until stable.

[0085] The microbial flora of the reactor during stable operation in the F3 stage is collected. The specific method is to take the fermentation broth, centrifuge at 4℃ for 10 minutes, remove the supernatant, and the precipitate part is the flora.

[0086] Example 2

[0087] This example is used to illustrate the enrichment method of the microbial flora.

[0088] 1. Reactor setup

[0089] Preparation of inoculum: In order to enrich anaerobic acid-producing microbial community, anaerobic digestion sludge from grain sugar factory, kitchen waste anaerobic digestion sludge, cellulose mesophilic anaerobic digestion sludge, glucose mesophilic anaerobic digestion sludge and fruit waste anaerobic fermentation acid-producing reactor sludge were mixed as inoculum. Different sources of inoculum were mixed in equal proportion according to total solids (TS) (TS and VTS of different sources of inoculum were shown in Table 1).

[0090] Preparation of substrate: Steam exploded straw, artificial kitchen waste (banana, orange, cabbage and rice were crushed and mixed in equal wet weight), and residual sludge from sewage plant were used as substrate. Different substrates were mixed in equal proportion according to volatile total solids (VTS) (TS and VTS of different substrates were shown in Table 1). The mixed substrate was stored at 4℃ and diluted to the target solid content when used.

[0091] Preparation of 1 mesophilic reactor (working volume 2.4 L).

[0092] 2. Reactor startup and operation

[0093] The present application starts 1 mesophilic reactor.

[0094] The whole operation process of the reactor is divided into F1, F2 and F3 stages. The organic load of straw is gradually increased in the three stages until stable operation in F3 stage. The operating conditions of the reactor in the three stages are shown in Table 2.

[0095] Days 0-105 are F1 stage,

[0096] The temperature of the mesophilic reactor was 37°C, the stirring speed was 100 rpm, and the pH value was controlled at 5.5-6.0. The inoculum source obtained by mixing inoculated sludge from multiple sources in equal proportions was broken by a blender and filtered with 2-3 layers of gauze to ensure that the solid content of the sludge used to start the reactor was below 5%. In order to inhibit the activity of methanogens, the starting sludge needed to be pretreated. The starting sludge was heat-treated at 80°C for 1 hour, and 5 mM of the methanogenesis inhibitor 2-bromoethanosulfophate (BES) was added. The pretreated mixed inoculum was injected into the working volume of the reactor, and the reactor was sealed after nitrogen was introduced to remove air and reach an anaerobic state. No material was fed into or discharged from the reactor for two days after starting the reactor, and then the substrate containing straw, kitchen waste, and sludge (TS: 5.2%; VTS: 4.1%; C / N ratio: 20) was supplied at an organic load of 0.5 g VTS / L / d, the VTS ratio of straw, kitchen waste, and sludge in the substrate was 1:1:1, the material was fed in and discharged every two days, the hydraulic retention time of the reactor was 100 days, and the physicochemical parameters of the reactor were monitored every four days.

[0097] Days 105-189 were the F2 phase, in which the hydraulic retention time was maintained at 100 days, the solid content of the feed was adjusted to 10%, the TS of the substrate was 10.3%, the VTS of the substrate was 8.2%, the VTS ratio of straw, kitchen waste, and sludge in the substrate was 1:1:1, the C / N ratio of the substrate was 20, and the organic load was increased to 1 g VTS / L / d, and the reactor was continuously operated until it was stable.

[0098] Days 189-368 were the F3 phase, in which the solid content of the feed was maintained at 10%, the organic load was increased to 2 g VTS / L / d, the hydraulic retention time was adjusted to 50 days, the TS of the substrate was 9.7%, the VTS of the substrate was 8.3%, the VTS ratio of straw, kitchen waste, and sludge in the feed was changed from 1:1:1 to 3:2:1, the proportion of straw was increased and the proportion of sludge was reduced, and the C / N ratio of the feed was increased from 20 to 40. The reactor was continuously operated until it was stable.

[0099] The microbial flora of the reactor during the stable operation of the F3 phase was collected. The specific collection method can be as follows: the fermentation broth was centrifuged at 4°C for 10 minutes, the supernatant was removed, and the precipitate was the microbial flora.

[0100] Table 2 shows the operating condition data of the reactor in different phases.

[0101] Table 2

[0102] F1 F2 F3 Substrate TS (%) 5.2 10.3 9.7 Substrate VTS (%) 4.1 8.2 8.3 Proportion of straw, kitchen waste and sludge in substrate VTS 1:1:1 1:1:1 3:2:1 C / N ratio of substrate 20 20 40 Organic load (g VTS / L / d) 0.5 1 2 Retention time (d) 100 100 50

[0103] Example 3

[0104] This embodiment is used to illustrate the method for obtaining organic acid mixture, xylose and lignin from lignocellulose (the detailed process flow is shown in Figure 1 ), which comprises the following steps:

[0105] Step one

[0106] (1) The corn stalks are crushed and impurities are removed, and the corn stalk raw material is impregnated with 2wt% dilute sulfuric acid, the amount of dilute sulfuric acid is 5 times the dry matter of corn stalks, impregnated at room temperature for 20 min, then treated at a pressure of 0.9 MPaG for 30 min, to obtain a pretreated material containing cellulose, xylose and lignin;

[0107] (2) The pretreated material is washed with water, the solid-liquid ratio used is 1:9, the washing is performed for 2 times, then centrifuged to obtain a liquid phase containing xylose, and a solid phase containing cellulose and lignin.

[0108] (3) The solid phase containing cellulose and lignin is subjected to alkali treatment, sodium hydroxide is used for alkali treatment, the amount of sodium hydroxide is 10% of the mass of the solid phase, the dry matter concentration of cellulose and lignin in alkali treatment is 15%, the temperature in alkali treatment is controlled at about 50℃, the treatment time is 2h, so that the lignin in the solid phase is dissolved, then centrifuged to obtain a liquid phase containing lignin, and a solid phase containing cellulose.

[0109] (4) The solid phase containing cellulose is washed with water, the solid-liquid ratio used is 1:7, the washing is performed for 3 times, then centrifuged to obtain a cellulose wet material, and a washing liquid containing lignin.

[0110] (5) The liquid phase containing lignin in step (3) and the washing liquid containing lignin in step (4) are combined and subjected to acid treatment. Sulfuric acid is used for acid treatment, the amount of sulfuric acid is 1.2 times the amount of sodium hydroxide, the temperature in acid treatment is controlled at about 40℃, the treatment time is 2h, the lignin is precipitated, then heated to 90℃ and kept for 1h, so that the precipitated lignin is aggregated into large particles, then vacuum belt filtration is used for solid-liquid separation to obtain a lignin wet material, the lignin wet material is subjected to airflow drying to obtain lignin.

[0111] Step two

[0112] The cellulose obtained in step one is subjected to acid production fermentation, and the bacterial flora used is the bacterial flora enriched in Example 2, the inoculation amount for acid production fermentation is 2%, the fermentation is carried out at a temperature of 37°C, a total solid content of 7.5%, pH=6, a nitrogen source of NH4Cl, and a C / N ratio of 40, and after 8 days of fermentation, 31.64 g / L of organic acid mixture is obtained, and the carbon conversion rate is 57%, among which, by using high performance liquid chromatography analysis, 17.13 g / L of lactic acid, 10.87 g / L of acetic acid, 2.95 g / L of propionic acid, and 0.69 g / L of butyric acid, isobutyric acid, valeric acid, iso-valeric acid and other volatile fatty acids are obtained.

[0113] Example 4

[0114] This example is used to illustrate a method for obtaining an organic acid mixture, xylose and lignin by using lignocellulose as raw material (the specific process flow is shown in Figure 1 ), which comprises the following steps:

[0115] Step one

[0116] (1) In step one, corn stalks are crushed and impurities are removed, and the corn stalk raw material is impregnated with 2wt% dilute sulfuric acid, the amount of dilute sulfuric acid is 5 times the dry matter of corn stalks, impregnation is carried out at room temperature for 20 min, and then the pretreated material containing cellulose, xylose and lignin is obtained by treating at a pressure of 0.9 MPaG for 30 min.

[0117] (2) The pretreated material is subjected to water washing, the solid-liquid ratio used is 1:9, and the water washing is carried out for 2 times, and then centrifugal separation is carried out to obtain a liquid phase containing xylose and a solid phase containing cellulose and lignin.

[0118] (3) The solid phase containing cellulose and lignin is subjected to alkali treatment, sodium hydroxide is used for alkali treatment, the amount of sodium hydroxide is 10% of the mass of the solid phase, the dry matter concentration of alkali treatment is 15%, the temperature during alkali treatment is controlled at about 50°C, the treatment time is 2h, the lignin in the solid phase is dissolved, and then centrifugal separation is carried out to separate the solid and liquid phases, and a liquid phase containing lignin and a solid phase containing cellulose are obtained.

[0119] (4) The solid phase containing cellulose is subjected to water washing, the solid-liquid ratio used is 1:7, and the water washing is carried out for 3 times, and then centrifugal separation is carried out to separate the solid and liquid phases, and cellulose wet material and water washing liquid containing lignin are obtained.

[0120] (5) Combine the lignin-containing liquid phase of step (3) and the lignin-containing water washing liquid of step (4) and perform acid treatment. The acid treatment uses sulfuric acid, and the amount of sulfuric acid is 1.2 times the amount of sodium hydroxide. The temperature of the acid treatment is controlled at about 40°C, and the treatment time is 2 hours. The lignin is precipitated, and then the temperature is raised to 90°C, and maintained for 1 hour, so that the precipitated lignin is aggregated into large particles. Then, vacuum belt filtration is used to separate the solid and liquid, to obtain lignin wet material. The lignin wet material is subjected to air flow drying, to obtain lignin.

[0121] Step two

[0122] The cellulose obtained in step one is subjected to acid production fermentation, and the bacterial flora used is the bacterial flora enriched in Example 2. The inoculation amount of the acid production fermentation is 2%, the temperature is 37°C, the total solid content is 10%, the pH is 6, the nitrogen source is NH4Cl, and the C / N ratio is 40. Under these conditions, the fermentation is carried out for 8 days, to obtain an organic acid mixture of 39.8g / L, and the carbon conversion rate is 54%. Among them, using high performance liquid chromatography analysis, lactic acid is 21.21g / L, acetic acid is 13.57g / L, propionic acid is 3.95g / L, and butyric acid, isobutyric acid, valeric acid, isovaleric acid and other volatile fatty acids are 1.1g / L.

[0123] Example 5

[0124] This example is used to illustrate a method for obtaining an organic acid mixture, xylose and lignin from lignocellulose (the specific process flow is shown in Figure 1 ), which includes the following steps:

[0125] Step one

[0126] (1) In step one, corn straw is crushed and impurities are removed, and the corn straw raw material is immersed with 2wt% dilute sulfuric acid. The amount of dilute sulfuric acid is 5 times the dry matter of corn straw. The immersion is carried out at room temperature for 20 minutes, and then the pretreated material containing cellulose, xylose and lignin is obtained by treating at a pressure of 0.9MPaG for 30 minutes.

[0127] (2) The pretreated material is washed with water. The solid-liquid ratio used for washing is 1:9, and the washing is carried out twice. Then, the liquid phase containing xylose and the solid phase containing cellulose and lignin are obtained by centrifugal separation.

[0128] (3) The solid phase containing cellulose and lignin is subjected to alkali treatment. Sodium hydroxide is used for alkali treatment, and the amount of sodium hydroxide is 10% of the mass of the solid phase. The dry matter concentration of the alkali treatment is 15%, and the temperature of the alkali treatment is controlled at about 50°C. The treatment time is 2 hours, so that the lignin in the solid phase is dissolved. Then, the solid and liquid are separated by centrifugal separation, to obtain a liquid phase containing lignin and a solid phase containing cellulose.

[0129] (4) The cellulose-containing solid phase is washed with water, the solid-liquid ratio is 1:7, the washing is performed 3 times, then centrifugal separation is performed to separate the solid and liquid, to obtain a cellulose wet material and a lignin-containing washing liquid.

[0130] (5) The lignin-containing liquid phase of step (3) and the lignin-containing washing liquid of step (4) are combined and subjected to acid treatment. The acid treatment uses sulfuric acid, the amount of sulfuric acid is 1.2 times the amount of sodium hydroxide, the acid treatment temperature is controlled at about 40°C, the treatment time is 2h, lignin is precipitated, then heated to 90°C, kept for 1h, to make the precipitated lignin aggregate into large particles, then vacuum belt filtration is used to separate the solid and liquid, to obtain a lignin wet material, the lignin wet material is subjected to air flow drying, to obtain lignin.

[0131] Step two

[0132] The cellulose obtained in step one is subjected to acid production fermentation, the enriched bacterial flora of example 1 is used, the inoculation amount of the acid production fermentation is 2%, the temperature is 53°C, the total solid content is 10%, the pH is 6, the nitrogen source is NH4Cl, the C / N ratio is 40, under the above conditions, the fermentation is performed for 14 days, to obtain an organic acid mixture of 26.28g / L, the carbon conversion rate is 32%, among which, high performance liquid chromatography analysis is used, to obtain lactic acid of 10.28g / L, acetic acid of 12.63g / L, propionic acid of 2.1g / L, butyric acid, isobutyric acid, valeric acid, isovaleric acid and other volatile fatty acids of 1.27g / L.

Claims

1. A method for the co-production of organic acids, xylose and lignin from lignocellulose, characterized in that, The method comprises the following steps: Step one, component separation of lignocellulosic raw materials to obtain cellulose, xylose and lignin; The method of component separation adopts alkali dissolution and acid precipitation method; Step two, acid-producing fermentation of cellulose in step one to obtain organic acid mixture; The acid-producing fermentation adopts anaerobic fermentation acid-producing microbial community; the anaerobic fermentation acid-producing microbial community is obtained by enrichment by the following method, which comprises F1 stage~F3 stage: F1 stage: Inoculum is added to the reactor, nitrogen is introduced to discharge air, and then the reactor is closed; the solid content of the inoculum is ≤5%; no material is fed into or discharged from the reactor for two days after starting the reactor, and then the substrate is supplied under the condition of 0.4~0.6 g VTS / L / d organic load; the C / N ratio of the substrate is 18~22; F2 stage: The solid content of the feed is adjusted to 8~12%, the organic load is increased to 0.8~1.2 g VTS / L / d, and the C / N ratio of the substrate is 18~22; F3 stage: In this stage, the solid content of the feed is kept at 8~12%, the organic load is increased to 1.8~2.2 g VTS / L / d, and the C / N ratio of the substrate is increased from 18~22 to 38~42; the microbial flora in the reactor in F3 stage is collected.

2. The method of co-producing organic acids, xylose and lignin from lignocellulose according to claim 1, characterized in that, In the step one, the alkali dissolution and acid precipitation method comprises the following steps: (1) first, pretreatment of the lignocellulosic raw material by one or a combination of pulverization and impurity removal, acid treatment, alkali treatment and steam explosion treatment to obtain pretreated material; (2) water washing and solid-liquid separation of the pretreated material to obtain liquid phase containing xylose and solid phase containing cellulose and lignin; (3) alkali treatment of the solid phase containing cellulose and lignin, solid-liquid separation to obtain liquid phase containing lignin and solid phase containing cellulose; (4) water washing and solid separation of the solid phase containing cellulose to obtain cellulose wet material and water washing liquid containing lignin; (5) combining the liquid phase containing lignin in step (3) and the water washing liquid containing lignin in step (4), and performing acid treatment, heating treatment and solid-liquid separation to obtain lignin wet material, and drying the lignin to obtain lignin.

3. The method of co-producing organic acids, xylose, and lignin from lignocellulose according to claim 1, wherein, In the step two, the conditions of the acid-producing fermentation are: anaerobic or batch fermentation, semi-continuous fermentation or continuous fermentation; and / or, the pH of the acid-producing fermentation is 5~10; the temperature of the acid-producing fermentation is 32~58℃; the C / N ratio is 20~60; the solid content is 2.5~15%; the fermentation time is 2~50 days.

4. The method of co-producing organic acids, xylose and lignin from lignocellulose according to claim 3, characterized in that, In the step two, the conditions of the acid-producing fermentation are: the pH of the acid-producing fermentation is 5~7; the temperature of the acid-producing fermentation is 35~53℃; the C / N ratio is 30~40; the solid content is 2.5~12%; the fermentation time is 7~21 days.

5. The method of co-producing organic acids, xylose, and lignin from lignocellulose according to claim 3, wherein, The nitrogen source is one or a combination of NH4Cl, corn syrup, sludge, potassium nitrate and urea.

6. The method for co-producing organic acid, xylose and lignin from lignocellulosic material according to claim 1, wherein, F1 stage: the running time of F1 stage is 80~120 days; The TS value of the substrate is 4.8-5.4%, and the VTS value is 4.0-4.4%; the substrate comprises a mixture of straw, kitchen waste and nitrogen source substrate; the feeding and discharging is carried out once every two days; the hydraulic retention time of the reactor is 90-110 days; F2 stage: The operation time of the F2 stage is 50-100 days; the TS of the substrate is 9.8-10.5%, and the VTS of the substrate is 8.0-8.5%; the hydraulic retention time of the reactor is 90-110 days; F3 stage: The operation time of the F3 stage is 120-200 days; the hydraulic retention time of the reactor is adjusted to 45-55 days, the TS of the substrate is 9.5-10%, and the VTS of the substrate is 8.0-8.6%.

7. The method for co-producing organic acid, xylose and lignin from lignocellulose according to claim 6, characterized in that, F1 stage: The VTS ratio of straw, kitchen waste and nitrogen source substrate in the substrate is (0.8-1.2):(0.8-1.2):(0.8-1.2); the nitrogen source substrate is residual sludge from a sewage plant; and the straw is steam exploded straw; F2 stage: The VTS ratio of straw, kitchen waste and nitrogen source substrate in the substrate is (0.8-1.2):(0.8-1.2):(0.8-1.2); F3 stage: The VTS ratio of straw, kitchen waste and nitrogen source substrate in the substrate is changed from (0.8-1.2):(0.8-1.2):(0.8-1.2) to (2.8-3.2):(1.8-2.2):(0.8-1.2).

8. The method of co-producing organic acids, xylose, and lignin from lignocellulose according to claim 6, wherein, The inoculum source is pretreated by heating at 75-85℃ for 0.5-1.2 hours and adding a methane inhibitor with a final concentration of 4-6 mM; the methane inhibitor is selected from 2-bromoethanesulfonic acid.

9. The method of lignocellulosic co-production of organic acids, xylose and lignin according to claim 6, characterized in that, The inoculum source comprises inoculums of different sources; the inoculums of different sources are selected from a mixture of anaerobic digestion sludge from a grain sugar factory, anaerobic digestion sludge from kitchen waste, cellulose anaerobic digestion sludge, glucose anaerobic digestion sludge and acid production reactor sludge from anaerobic fermentation of fruit waste.

10. The method of lignocellulose co-production of organic acids, xylose and lignin according to claim 9, characterized in that, The cellulose anaerobic digestion sludge is selected from cellulose high-temperature anaerobic digestion sludge or cellulose mesophilic anaerobic digestion sludge.

11. The method of lignocellulosic co-production of organic acids, xylose and lignin according to claim 9, characterized in that, The glucose anaerobic digestion sludge is selected from glucose high-temperature anaerobic digestion sludge or glucose mesophilic anaerobic digestion sludge.

12. The method of lignocellulosic co-production of organic acids, xylose and lignin according to claim 9, characterized in that, The inoculum source comprises mixing the inoculums of different sources according to the total solid concentration, and each sludge accounts for more than 10% of the total solid concentration.

13. The method of lignocellulose co-production of organic acids, xylose and lignin according to claim 12, characterized in that, Each sludge is mixed according to the total solid concentration in equal proportions.

14. The method of lignocellulosic co-production of organic acids, xylose and lignin according to claim 9, characterized in that, The reactor is a high-temperature reactor or a mesophilic reactor.

15. The method of lignocellulosic co-production of organic acids, xylose and lignin according to claim 14, characterized in that, The pH value of the reactor is 5.5-6.0; and / or, the working temperature of the high-temperature reactor is 50-55℃; and / or, the working temperature of the mesophilic reactor is 35-40℃.

16. The method for co-producing organic acid, xylose and lignin from lignocellulose according to claim 14, characterized in that, when the reactor is a thermophilic reactor, the cellulose anaerobic digestion sludge is selected from the group consisting of cellulose thermophilic anaerobic digestion sludge, the glucose anaerobic digestion sludge is selected from the group consisting of glucose thermophilic anaerobic digestion sludge; when the reactor is a mesophilic reactor, the cellulose anaerobic digestion sludge is selected from the group consisting of cellulose mesophilic anaerobic digestion sludge, the glucose anaerobic digestion sludge is selected from the group consisting of glucose mesophilic anaerobic digestion sludge.

17. The method of lignocellulosic co-production of organic acids, xylose and lignin according to claim 1, characterized in that, the organic acid is a plurality of combinations of lactic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid.

Images