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

Abstract

The present application provides a method for producing organic acid and lignin from lignocellulose, comprising the following steps: step one, pretreating lignocellulose raw material to obtain pretreated material; step two, producing acid fermentation on the pretreated material containing cellulose, xylose and lignin to obtain solid-liquid mixed fermentation liquor containing organic acid mixture and lignin; step three, separating the solid-liquid mixed fermentation liquor containing organic acid mixture and lignin to obtain liquid phase containing organic acid mixture and solid phase containing lignin; step four, extracting lignin from the solid phase containing lignin to obtain lignin. The method provided by the present application has a simple reaction system, can efficiently separate lignin, and can obtain various organic acids through a simple process.

Description

Technical Field

[0001] This invention relates to the technical field of biochemical production, and more specifically, to a method for the co-production of organic acids and lignin from lignocellulose. Background Technology

[0002] Lignocellulose is mainly composed of lignin, hemicellulose, and cellulose, and it is widely found in the stems, leaves, and pericarps of plants. Currently, people utilize lignocellulose to separate lignin, hemicellulose, and cellulose; simultaneously, they convert these polymers into other usable intermediate raw materials. For example, lignocellulose can be converted into important industrial raw materials such as ethanol, polyhydroxyalkanoates, and organic acids through hydrolysis and fermentation.

[0003] Organic acids can be obtained through enzymatic fermentation, microbial fermentation, and other methods. In recent years, people have used lignocellulose as a raw material to prepare a variety of organic acids. For example, patent CN114032257A provides a method for the co-production of lactic acid, xylitol, and lignin from lignocellulose raw materials. This method first enzymatically hydrolyzes cellulose into glucose, and then ferments the glucose to obtain lactic acid. In this method, most of the acid-producing raw materials are separated, which is not conducive to the production of lactic acid. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for the co-production of organic acids and lignin from lignocellulose. The reaction system is simple, lignin can be efficiently separated, and a variety of organic acids can be obtained through a simple process.

[0005] The purpose of this invention is to provide a method for the co-production of organic acids and lignin from lignocellulose, comprising the following steps:

[0006] Step 1: Pre-treat the lignocellulose raw material to obtain pre-treated material;

[0007] Step 2: Perform acid-producing fermentation on the pretreated material from Step 1 to obtain a solid-liquid mixed fermentation broth containing a mixture of organic acids and lignin;

[0008] Step 3: Perform solid-liquid separation on the solid-liquid mixed fermentation broth containing organic acid mixture and lignin from Step 2 to obtain a liquid phase containing organic acid mixture and a solid phase containing lignin.

[0009] Step 4: Extract lignin from the lignin-containing solid phase obtained in Step 3 to obtain lignin.

[0010] Preferably, the lignin cellulose raw material in this invention is derived from one or more of the following: corn stalks, rice stalks, wheat stalks, reeds, corn cobs, and soybean stalks.

[0011] Preferably, in step one, the method for pretreating the lignocellulose raw material is as follows: after the lignocellulose raw material is crushed and impurities are removed, it is subjected to acid treatment, alkali treatment, and steam explosion treatment to obtain the pretreated material.

[0012] Preferably, the lignocellulosic raw material is crushed and impurity removed using a complete set of crushing and impurity removal equipment, which includes coarse crushing, impurity and iron removal, fine crushing, and dust removal.

[0013] Preferably, in step two, the pretreated material is directly subjected to acid-producing fermentation, and the conditions for acid-producing fermentation are as follows:

[0014] Batch fermentation, semi-continuous fermentation, or continuous fermentation is carried out under anaerobic conditions; the pH of acid-producing fermentation is 5-10; preferably 5-7; the temperature of acid-producing fermentation is 35-55℃; preferably 37-53℃; the C / N ratio is 30-60; preferably 30-40; the solid content is 2.5-15%; preferably 2.5-10%; the fermentation time is 2-50 days; preferably 7-21 days.

[0015] It is worth mentioning that, in this invention, the main components of the pretreated material include cellulose, xylose, and lignin.

[0016] Preferably, the nitrogen source is one or a combination of NH4Cl, corn steep liquor, sludge, potassium nitrate, and urea.

[0017] Preferably, the acid-producing fermentation of the present invention uses an acid-producing microbial community; more preferably, it uses an anaerobic fermentation acid-producing microbial community enriched by the method provided in patent application (application number 2023113103664).

[0018] Specifically, the enrichment method for anaerobic fermentation acid-producing microbial communities includes stages F1 to F3. The reactor's operation can be divided into three stages: F1, F2, and F3. The organic loading of straw is gradually increased in each stage until stable operation is achieved in stage F3. Stage F1 is the reactor start-up stage, with low solids content and loading. Increasing the solids content and loading leads to stage F2. After acid production stabilizes in F2, the proportion of straw in the material is increased, raising the C / N ratio, leading to stage F3, where the microbial community adapts to the high C / N ratio straw material.

[0019] Specifically as follows:

[0020] F1 Stage:

[0021] The F1 stage takes 80 to 120 days, preferably 100 to 110 days;

[0022] Add the inoculum to the reactor, purge with nitrogen to remove air, and then seal the reactor. Do not feed or discharge any material for two days after starting the reactor. After that, supply the substrate under an organic load of 0.4–0.6 g VTS / L / d. The TS value of the substrate is 4.8–5.4%, the VTS value is 4.0–4.4%, and the C / N ratio is 18–22. Feed and discharge can be performed once every two days. The hydraulic retention time of the reactor is 90–110 days. The physicochemical parameters of the reactor can be monitored every four days.

[0023] Specifically, regarding the source of vaccination:

[0024] The solid content of the inoculum used in this invention is ≤5%.

[0025] Furthermore, to inhibit the activity of methanogens, it is preferable to pretreat the inoculum source. The pretreatment method involves heat-treating the inoculum source at 75–85°C for 0.5–1.2 hours and adding a methane inhibitor at a final concentration of 4–6 mM. Preferably, the methane inhibitor is 2-bromoethanosulfonic acid (BES).

[0026] Furthermore, the inoculum source can include inoculum from different sources; specifically, the inoculum from different sources can be selected from a mixture of anaerobic digestion sludge from grain and sugar mills, anaerobic digestion sludge from kitchen waste, anaerobic digestion sludge from cellulose, anaerobic digestion sludge from glucose, and sludge from anaerobic fermentation and acid production reactors from fruit waste. Among these, the cellulose anaerobic digestion sludge is preferably either thermophilic or mesophilic cellulose anaerobic digestion sludge; the glucose anaerobic digestion sludge is preferably either thermophilic or mesophilic glucose anaerobic digestion sludge. The appropriate sludge type can be selected based on different reaction temperatures.

[0027] Furthermore, the inoculum source comprises inoculum from different sources mixed according to total solids (TS), with each type of sludge accounting for more than 10% of the total solids (TS), and more preferably, multiple inoculum sludges from different sources are mixed in equal proportions according to the total solids (TS).

[0028] In practice, the inoculum source can be crushed with a mixer and then filtered (for example, filtered with 2-3 layers of gauze) to ensure that the solid content of the sludge is below 5% when the reactor is started.

[0029] Specifically, regarding the substrate:

[0030] The substrate used in this invention is a mixture containing straw, kitchen waste and nitrogen source substrate; in the F1 stage, the preferred 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).

[0031] Furthermore, the source substrate can be any substrate commonly used in the field, specifically wastewater treatment plant sludge. Currently, a large amount of wastewater is generated during the activated sludge process in urban wastewater treatment plants in my country. However, the sludge treatment technology is not yet mature. Using wastewater treatment plant sludge as a nitrogen source substrate can reuse the sludge, which is environmentally friendly and cost-effective.

[0032] Furthermore, the straw may be selected from at least one or a combination of corn straw, rice straw, wheat straw, reeds or bean straw.

[0033] Furthermore, the straw can be steam-exploded straw. Steam-exploded straw can be straw that has undergone conventional steam explosion treatment in this field, or it can be prepared by the following method: adding straw material and water to a sealed container, maintaining it for a period of time (which can be a few minutes), and then suddenly reducing the pressure to steam-explode the straw material, thereby destroying the hemicellulose and lignin bonding layer, exposing more active groups of cellulose, which is more conducive to degradation.

[0034] Furthermore, food waste can be regular food waste or homemade waste, such as wet waste containing crushed fruits, vegetables, and grains.

[0035] Preferably, the substrate can be stored at low temperature (e.g., 4°C) and diluted to the target solids content before use.

[0036] Specifically, regarding the reactor:

[0037] The reactor used in this invention can be a high-temperature reactor or a medium-temperature reactor. Conventional reactors in the art can be selected, such as conventional mechanically stirred tanks. The stirring speed of the reactor can be 0–150 ppm, sufficient to ensure uniform mixing of the materials.

[0038] Preferably, the pH value of the reactor is 5.5 to 6.0; the operating temperature of the high-temperature reactor is 50 to 55°C; and the operating temperature of the medium-temperature reactor is 35 to 40°C.

[0039] Furthermore, 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.

[0040] Furthermore, when the reactor is a mesophilic reactor, the cellulose anaerobic digestion sludge can be selected from cellulose mesophilic anaerobic digestion sludge, and the glucose anaerobic digestion sludge can be selected from glucose mesophilic anaerobic digestion sludge.

[0041] In practice, a semi-continuous fully mixed-flow anaerobic fermentation acid-producing reactor system can be constructed, using either a high-temperature reactor or a mesophilic reactor to enrich high-temperature and mesophilic bacterial communities, respectively.

[0042] F2 phase:

[0043] The operating time of the F2 stage is 50–100 days, preferably 75–90 days; the reactor pH is 5.5–6.0; the feed solids content is adjusted to 8–12%, and the organic load is increased to 0.8–1.2 g VTS / L / d for substrate supply, with substrate TS of 9.8–10.5% and substrate VTS of 8.0–8.5%, and 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 it should be continuously operated until it stabilizes.

[0044] F3 stage:

[0045] The operating time for stage F3 is 120–200 days, preferably 165–185 days; the reactor pH is 5.5–6.0; the feed solids content remains constant during this stage (8–12%), while the organic loading is increased to 1.8–2.2 g. Substrate was supplied at VTS / L / d, and the hydraulic retention time was adjusted to 45–55 days. The VTS ratio of straw, kitchen waste, and sludge in the feed was 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 was increased from 18–22 to 38–42. The substrate TS was 9.5–10%, and the substrate VTS was 8.0–8.6%. Feeding and discharging were carried out every two days. The operation continued until stable. Microbial communities in the reactor were collected during the stable operation of the F3 stage.

[0046] It is worth mentioning that the microbial community of the reactor during the stable operation of the F3 stage was collected by taking the fermentation broth, centrifuging it at 4°C for 10 minutes, removing the supernatant, and the precipitate being the microbial community. The enriched microbial community was used for the acid-producing fermentation of the pretreated materials of this invention.

[0047] Furthermore, after the pretreated material undergoes acid-producing fermentation, a liquid phase containing a mixture of organic acids and a solid phase containing lignin are obtained. In order to separate the solid and liquid, plate and frame filtration or centrifugation can be used to separate the solid-liquid mixture into a liquid phase containing organic acids and a solid phase containing lignin.

[0048] Preferably, in step four, lignin is extracted using an alkali-dissolution-acid-precipitation method. Specifically, the alkali-dissolution-acid-precipitation method includes the following steps:

[0049] (1) Alkali dissolution: The solid phase of lignin is dissolved by an alkaline solution to obtain an alkaline solution containing lignin;

[0050] (2) Solid-liquid separation: The lignin alkaline solution is centrifuged to obtain a solution containing lignin;

[0051] (3) Acid precipitation: Acid is added to precipitate lignin, and wet lignin is obtained by solid-liquid separation;

[0052] (4) Washing: The wet lignin is washed with water and centrifuged to obtain the washed wet lignin;

[0053] (5) Drying: The wet lignin washed with water is dried to obtain lignin.

[0054] Preferably, after the pretreated material undergoes acid-producing fermentation, a fermentation broth containing a mixture of organic acids is obtained, wherein the organic acids in the fermentation broth are a combination of lactic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, and isovaleric acid.

[0055] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a method for using lignocellulose as a raw material to replace grain raw materials and co-produce mixed organic acids and lignin. The composition and content of acids in the mixed organic acids can be adjusted by controlling the acid-producing fermentation conditions. The lignocellulose as a raw material does not require enzymatic hydrolysis after pretreatment, resulting in low cost. Attached Figure Description

[0056] Figure 1 This is a flowchart illustrating the co-production of organic acids and lignin from lignocellulose using this invention. Detailed Implementation

[0057] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0058] Unless otherwise specified, the raw materials used in the embodiments are all publicly available in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0059] The sources of sludge, kitchen waste, and straw used in the embodiments of the present invention are as follows:

[0060] Anaerobic digestion sludge from grain and sugar mills: COFCO Biochemical (Chengdu) Co., Ltd.;

[0061] Anaerobic digestion sludge from food waste: An anaerobic methanogenic reactor that operates stably at the Environmental Biotechnology Research Center of the School of Architecture and Environment, Sichuan University. The food waste is taken from the student canteen of Sichuan University.

[0062] Cellulose high-temperature anaerobic digestion sludge: The high-temperature anaerobic methanogenic reactor, stably operated by the Environmental Biotechnology Research Center of the School of Architecture and Environment, Sichuan University, uses commercially available carboxymethyl cellulose as a carbon source.

[0063] Cellulose mesophilic anaerobic digestion sludge: A mesophilic anaerobic methanogenic reactor stably operating at the Environmental Biotechnology Research Center of the School of Architecture and Environment, Sichuan University, using commercially available carboxymethyl cellulose as a carbon source.

[0064] High-temperature anaerobic digestion of glucose sludge: A high-temperature anaerobic methanogenic reactor that is operating stably at the Environmental Biotechnology Research Center of the School of Architecture and Environment, Sichuan University, using commercially available glucose as a carbon source.

[0065] Mesophilic anaerobic digestion of glucose sludge: A stable-running mesophilic anaerobic methanogenic reactor at the Environmental Biotechnology Research Center of the School of Architecture and Environment, Sichuan University, using commercially available glucose as a carbon source.

[0066] Sludge from the anaerobic fermentation acid-producing reactor for fruit waste: The anaerobic fermentation acid-producing reactor, which is stably operating at the Environmental Biotechnology Research Center of the School of Architecture and Environment, Sichuan University, uses commercially available fruits (a mixture of bananas, watermelons, and oranges in a weight ratio of 1:1:1) as raw materials.

[0067] The wastewater treatment plant's residual sludge is dewatered sludge from a wastewater treatment plant in Chengdu.

[0068] Artificially prepared food waste is made by mixing pulverized bananas, oranges, cabbage, and rice by wet weight;

[0069] Steam-exploded straw refers to straw that has been blasted by steam. The steam blasting process includes: adding corn stalks and water to a sealed container, maintaining a pressure of 1.7 MPa for 2 minutes, and then suddenly reducing the pressure to blast the straw material with steam.

[0070] Table 1 shows the TS and VTS data for inoculum and substrate from different sources.

[0071] Table 1

[0072]

[0073] In the example, one high-temperature reactor (working volume 4L) and one mesophilic reactor (working volume 2.4L) were prepared to enrich microbial communities suitable for high temperatures and mesophilic communities, respectively.

[0074] Example 1

[0075] This embodiment illustrates a method for enriching microbial communities.

[0076] 1. Reactor Construction

[0077] Preparation of inoculum source: In order to enrich the anaerobic fermentation acid-producing microbial community, anaerobic digestion sludge from grain and sugar mills, anaerobic digestion sludge from kitchen waste, high-temperature anaerobic digestion sludge from cellulose, high-temperature anaerobic digestion sludge from glucose, and sludge from anaerobic fermentation acid-producing reactors from fruit waste were mixed as inoculum source; inoculum from different sources were mixed in equal proportions (i.e., 1:1:1:1:1) according to the total solids (TS) concentration (TS and VTS of inoculum from different sources are shown in Table 1).

[0078] Substrate preparation: Steam-exploded straw, artificially prepared kitchen waste (a mixture of crushed bananas, oranges, cabbage, and rice, mixed by wet weight), and wastewater treatment plant sludge were used as substrates. Different substrates were mixed in equal proportions according to their volatile total solids (VTS) concentration (TS and VTS for each substrate are shown in Table 1). The mixed substrates were stored at 4°C and diluted to the target solids content before use.

[0079] Prepare one high-temperature reactor (working volume 4L, named H).

[0080] 2. Reactor Start-up and Operation

[0081] This invention starts a high-temperature reactor (H).

[0082] The reactor's entire operation process is divided into three stages: F1, F2, and F3. The organic load of straw is gradually increased in each stage until stable operation is achieved in stage F3. The operating conditions of the reactor in each stage are shown in Table 2.

[0083] Days 0 to 105 constitute the F1 stage.

[0084] The high-temperature reactor was started and operated at 53℃, with a stirring speed of 100 rpm and a pH value controlled between 5.5 and 6.0. The inoculum source, obtained by mixing inoculating sludge from various sources in equal proportions according to the TS (Standard Test), was crushed using a mixer and filtered through 2-3 layers of gauze to ensure the solid content of the reactor start-up sludge was below 5%. To inhibit methanogenic bacteria activity, the start-up sludge required pretreatment. The start-up sludge was heat-treated at 80℃ for 1 hour, and a methane inhibitor, 2-bromoethanosulfophate (BES), was added to a final concentration of 5 mM. The pretreated mixed inoculum was injected into the reactor's working volume, nitrogen was introduced to purge air to achieve an anaerobic state, and the reactor was then sealed. For the first two days after reactor startup, no feed or discharge was performed. Afterward, a substrate consisting of straw, kitchen waste, and sludge (TS: 5.2%; VTS: 4.1%; C / N ratio: 20) was supplied under an organic loading of 0.5 g VTS / L / d. The VTS ratio of straw, kitchen waste, and sludge in the substrate was 1:1:1. Feed and discharge were performed every two days. The hydraulic retention time of the reactor was 100 days. The reactor's physicochemical parameters were monitored every four days.

[0085] Days 105 to 189 are the F2 phase.

[0086] During this stage, the hydraulic retention time is maintained at 100 days, the feed solids content is adjusted to 10%, the substrate TS is 10.3%, the substrate VTS is 8.2%, the VTS ratio of straw, kitchen waste and sludge in the substrate is 1:1:1, the substrate C / N ratio is 20, the organic load is increased to 1g VTS / L / d, and the operation continues until it stabilizes.

[0087] Days 189 to 368 are the F3 phase.

[0088] During this phase, the feed solids content was maintained at 10%, the organic loading rate was increased to 2 g VTS / L / d, the hydraulic retention time was adjusted to 50 days, the substrate TS was 9.7%, the substrate VTS was 8.3%, and the VTS ratio of straw, kitchen waste, and sludge in the feed was changed from 1:1:1 to 3:2:1, increasing the proportion of straw and decreasing the proportion of sludge, thus raising the feed C / N ratio from 20 to 40. This process continued until stability was achieved.

[0089] The microbial community of the reactor during the stable operation of the F3 stage was collected by taking the fermentation broth, centrifuging it at 4°C for 10 minutes, removing the supernatant, and the precipitate was the microbial community.

[0090] Example 2

[0091] This embodiment illustrates a method for enriching microbial communities.

[0092] 1. Reactor Construction

[0093] Preparation of inoculum sources: In order to enrich the anaerobic fermentation acid-producing microbial community, anaerobic digestion sludge from grain and sugar mills, anaerobic digestion sludge from kitchen waste, mesophilic anaerobic digestion sludge from cellulose, mesophilic anaerobic digestion sludge from glucose, and sludge from anaerobic fermentation acid-producing reactors from fruit waste were mixed as inoculum sources; inoculum sources from different sources were mixed in equal proportions according to total solids (TS) concentration (TS and VTS of inoculum sources from different sources are shown in Table 1).

[0094] Substrate preparation: Steam-exploded straw, artificially prepared kitchen waste (a mixture of crushed bananas, oranges, cabbage, and rice, mixed by wet weight), and wastewater treatment plant sludge were used as substrates. Different substrates were mixed in equal proportions according to their volatile total solids (VTS) concentration (TS and VTS for each substrate are shown in Table 1). The mixed substrates were stored at 4°C and diluted to the target solids content before use.

[0095] Prepare one medium-temperature reactor (working volume 2.4L).

[0096] 2. Reactor Start-up and Operation

[0097] This invention starts a medium-temperature reactor.

[0098] The reactor's entire operation process is divided into three stages: F1, F2, and F3. The organic load of straw is gradually increased in each stage until stable operation is achieved in stage F3. The operating conditions of the reactor in each stage are shown in Table 2.

[0099] Days 0 to 105 constitute the F1 stage.

[0100] The mesophilic reactor was started and operated at 37°C with a stirring speed of 100 rpm and a pH value controlled between 5.5 and 6.0. The inoculum source, obtained by mixing sludge from various sources in equal proportions according to the TS (Standard Test), was crushed using a mixer and filtered through 2-3 layers of gauze to ensure the solid content of the reactor start-up sludge was below 5%. To inhibit methanogenic bacteria activity, the start-up sludge required pretreatment. The start-up sludge was heat-treated at 80°C for 1 hour, and a methane inhibitor, 2-bromoethanosulfophate (BES), was added to a final concentration of 5 mM. The pretreated mixed inoculum was injected into the reactor's working volume, nitrogen was introduced to purge air to achieve an anaerobic state, and the reactor was then sealed. For the first two days after reactor startup, no feed or discharge was performed. Afterward, a substrate consisting of straw, kitchen waste, and sludge (TS: 5.2%; VTS: 4.1%; C / N ratio: 20) was supplied under an organic loading of 0.5 g VTS / L / d. The VTS ratio of straw, kitchen waste, and sludge in the substrate was 1:1:1. Feed and discharge were performed every two days. The hydraulic retention time of the reactor was 100 days. The reactor's physicochemical parameters were monitored every four days.

[0101] Days 105 to 189 are the F2 phase.

[0102] During this stage, the hydraulic retention time is maintained at 100 days, the feed solids content is adjusted to 10%, the substrate TS is 10.3%, the substrate VTS is 8.2%, the VTS ratio of straw, kitchen waste and sludge in the substrate is 1:1:1, the substrate C / N ratio is 20, and the organic load is increased to 1g VTS / L / d, and the operation continues until it stabilizes.

[0103] Days 189 to 368 are the F3 phase.

[0104] During this phase, the feed solids content was maintained at 10%, the organic loading rate was increased to 2 g VTS / L / d, the hydraulic retention time was adjusted to 50 days, the substrate TS was 9.7%, the substrate VTS was 8.3%, and the VTS ratio of straw, kitchen waste, and sludge in the feed was changed from 1:1:1 to 3:2:1, increasing the proportion of straw and decreasing the proportion of sludge, thus raising the feed C / N ratio from 20 to 40. This process continued until stability was achieved.

[0105] To collect the reactor microbial community during the stable operation of the F3 stage, the specific collection method is as follows: take the fermentation broth, centrifuge at 4℃ for 10 minutes, remove the supernatant, and the precipitate is the microbial community.

[0106] Table 2 shows the operating conditions data for different stages of the reactor.

[0107] Table 2

[0108] F1 F2 F3 Substrate TS (%) 5.2 10.3 9.7 Substrate VTS (%) 4.1 8.2 8.3 The proportion of straw, kitchen waste and sludge VTS in the substrate 1:1:1 1:1:1 3:2:1 substrate C / N ratio 20 20 40 Organic loading (gVTS / L / d) 0.5 1 2 Duration of stay (d) 100 100 50

[0109] Example 3

[0110] This embodiment illustrates a method for obtaining an organic acid mixture and lignin from lignocellulose (see detailed process flow). Figure 1 The process includes the following steps:

[0111] Step 1: Crush and remove impurities from the corn stalks, and soak the corn stalk raw material in water. The amount of water is 8 times that of the dry corn stalks. Soak at room temperature for 30 minutes, and then treat at a pressure of 1.7 MPaG for 40 minutes to obtain pretreated material containing cellulose, xylose and lignin.

[0112] Step 2: The pretreated material obtained in Step 1 is subjected to acid-producing fermentation. The microbial community used is the microbial community enriched in Example 2. The inoculum amount for acid-producing fermentation is 2%, the temperature is 37°C, the total solid content is 5%, the pH is 6, the nitrogen source is NH4Cl, and the C / N ratio is 40. Fermentation is carried out for 21 days to obtain a liquid phase containing a mixture of organic acids and a solid phase containing lignin.

[0113] Step 3: The solid-liquid mixed fermentation broth containing mixed organic acids and lignin obtained in Step 2 is centrifuged to obtain a liquid phase containing mixed organic acids and a solid phase containing lignin. The mixed organic acid concentration is 10.9 g / L, with a carbon conversion rate of 26%. High-performance liquid chromatography (HPLC) analysis revealed acetic acid 6.32 g / L, butyric acid 3.99 g / L, and other volatile fatty acids such as lactic acid, propionic acid, isobutyric acid, valeric acid, and isovaleric acid at 0.58 g / L.

[0114] Step 4: Extract lignin from the lignin-containing solid phase. The specific steps are as follows:

[0115] (1) Alkali dissolution: Sodium hydroxide is used to dissolve the lignin in the solid phase. The amount of sodium hydroxide is 11% of the dry solid phase, and the mass of water added is 7 times the mass of the dry solid phase. The treatment time is 2 hours to obtain an alkaline solution of lignin.

[0116] (2) Solid-liquid separation: The above lignin alkaline solution is separated by centrifugation to obtain a solution containing lignin;

[0117] (3) Acid precipitation: Add sulfuric acid at room temperature to precipitate lignin. The mass of sulfuric acid used is 1.15 times the mass of sodium hydroxide used. Then, centrifugation is used to separate the wet lignin.

[0118] (4) Washing: The wet lignin is washed with water, the amount of water being 8 times that of the dry wet lignin, and then centrifuged to obtain the washed wet lignin.

[0119] (5) Drying: The wet lignin that has been washed with water is dried by airflow to obtain lignin.

[0120] Example 4

[0121] This embodiment illustrates a method for obtaining an organic acid mixture and lignin from lignocellulose (see detailed process flow). Figure 1 The process includes the following steps:

[0122] Step 1: Crush and remove impurities from the corn stalks, and impregnate the corn stalk raw material with 2wt% dilute sulfuric acid. The amount of dilute sulfuric acid used is 5 times that of the dry corn stalks. Impregnate at room temperature for 20 minutes, and then treat under a pressure of 0.9MPaG for 30 minutes to obtain a pretreated material containing cellulose, xylose and lignin.

[0123] Step 2: The pretreated material obtained in Step 1 is subjected to acid-producing fermentation. The microbial community used is the microbial community enriched in Example 2. The inoculum amount for acid-producing fermentation is 2%, the temperature is 37°C, the total solid content is 5%, the pH is 6, the nitrogen source is NH4Cl, and the C / N ratio is 40. Fermentation is carried out for 21 days to obtain a liquid phase containing a mixture of organic acids and a solid phase containing lignin.

[0124] Step 3: The solid-liquid mixed fermentation broth containing mixed organic acids and lignin obtained in Step 2 is centrifuged to separate the liquid phase containing mixed organic acids and the solid phase containing lignin. The mixed organic acid concentration is 21.16 g / L, with a carbon conversion rate of 46%. High-performance liquid chromatography (HPLC) analysis revealed lactic acid 10.46 g / L, acetic acid 6.71 g / L, propionic acid 2.04 g / L, valeric acid 1.34 g / L, and other volatile fatty acids such as butyric acid, isobutyric acid, and isovaleric acid 0.6 g / L.

[0125] Step four involves lignin extraction from the lignin-containing solid phase. The specific steps are as follows:

[0126] (1) Alkali dissolution: Sodium hydroxide is used to dissolve the lignin in the solid phase. The amount of sodium hydroxide is 11% of the dry solid phase, and the mass of water added is 7 times the mass of the dry solid phase. The treatment time is 2 hours to obtain an alkaline solution of lignin.

[0127] (2) Solid-liquid separation: The above lignin alkaline solution is separated by centrifugation to obtain a solution containing lignin;

[0128] (3) Acid precipitation: Add sulfuric acid at room temperature to precipitate lignin. The amount of sulfuric acid used is 1.15 times that of sodium hydroxide. Then, centrifuge to obtain wet lignin.

[0129] (4) Washing: The wet lignin is washed with water, the amount of water being 8 times that of the dry wet lignin, and then centrifuged to obtain the washed wet lignin.

[0130] (5) Drying: The wet lignin that has been washed with water is dried by airflow to obtain lignin.

[0131] Example 5

[0132] This embodiment illustrates a method for obtaining an organic acid mixture and lignin from lignocellulose (see detailed process flow). Figure 1 The process includes the following steps:

[0133] Step 1: Crush and remove impurities from the corn stalks, and impregnate the corn stalk raw material with 2wt% dilute sulfuric acid. The amount of dilute sulfuric acid used is 5 times that of the dry corn stalks. Impregnate at room temperature for 20 minutes, and then treat under a pressure of 0.9MPaG for 30 minutes to obtain a pretreated material containing cellulose, xylose and lignin.

[0134] Step 2: The pretreated material obtained in Step 1 is subjected to acid-producing fermentation. The microbial community used is the microbial community enriched in Example 1. The inoculum amount for acid-producing fermentation is 2%, the temperature is 53℃, the total solid content is 5%, the pH is 6, the nitrogen source is NH4Cl, and the C / N ratio is 40. Fermentation is carried out for 21 days to obtain a liquid phase containing a mixture of organic acids and a solid phase containing lignin.

[0135] Step 3: The solid-liquid mixed fermentation broth containing mixed organic acids and lignin obtained in Step 2 is centrifuged to separate the liquid phase containing mixed organic acids and the solid phase containing lignin. The mixed organic acid concentration is 21.45 g / L, with a carbon conversion rate of 49%. High-performance liquid chromatography (HPLC) analysis revealed lactic acid 1.6 g / L, acetic acid 7.98 g / L, propionic acid 10.23 g / L, butyric acid 1.22 g / L, and other volatile fatty acids such as isobutyric acid, valeric acid, and isovaleric acid at 0.4 g / L.

[0136] Step four involves lignin extraction from the lignin-containing solid phase. The specific steps are as follows:

[0137] (1) Alkali dissolution: Sodium hydroxide is used to dissolve the lignin in the solid phase. The amount of sodium hydroxide is 11% of the dry solid phase, and the mass of water added is 7 times the mass of the dry solid phase. The treatment time is 2 hours to obtain an alkaline solution of lignin.

[0138] (2) Solid-liquid separation: The above lignin alkaline solution is separated by centrifugation to obtain a solution containing lignin;

[0139] (3) Acid precipitation: Add sulfuric acid at room temperature to precipitate lignin. The amount of sulfuric acid used is 1.15 times that of sodium hydroxide. Then, centrifuge to obtain wet lignin.

[0140] (4) Washing: The wet lignin is washed with water, the amount of water being 8 times that of the dry wet lignin, and then centrifuged to obtain the washed wet lignin.

[0141] (5) Drying: The wet lignin that has been washed with water is dried by airflow to obtain lignin.

Claims

1. A method for the co-production of organic acids and lignin from lignocellulose, characterized in that, The method comprises the following steps: Step one, pretreating the lignocellulosic raw material to obtain pretreated material; Step two, producing acid fermentation on the pretreated material of step one to obtain a solid-liquid mixed fermentation liquor containing organic acid mixture and lignin; Step three, performing solid-liquid separation on the solid-liquid mixed fermentation liquor containing organic acid mixture and lignin of step two to obtain a liquid phase containing organic acid mixture and a solid phase containing lignin; Step four, extracting lignin from the solid phase containing lignin of step three to obtain lignin; The acid-producing fermentation uses an anaerobic fermentation acid-producing microbial community enriched by the following F1 stage-F3 stage method; F1 stage: Add the inoculum to the reactor, and after purging the air with nitrogen, seal the reactor; the solid content of the inoculum is ≤5%; do not feed or discharge the material for two days after starting the reactor, and then supply the substrate under the condition of 0.4-0.6 g VTS / L / d organic load; the C / N ratio is 18-22; wherein, VTS is volatile solid concentration; F2 stage: Adjust the feed solid content to 8-12%, and increase the organic load to 0.8-1.2 g VTS / L / d, and the substrate C / N ratio is 18-22; F3 stage: This stage maintains the feed solid content at 8-12%, increases the organic load to 1.8-2.2 g VTS / L / d, and increases the substrate C / N ratio from 18-22 to 38-42; collect the microbial flora in the F3 stage reactor.

2. The method of lignocellulose co-production of organic acids and lignin according to claim 1, characterized in that, In the step one, the lignocellulosic raw material is derived from one or more of corn stalks, rice straw, wheat straw, reed, corn cob and bean straw.

3. The method of lignocellulose co-production of organic acids and lignin according to claim 1, characterized in that, In the step one, the method for pretreating the lignocellulosic raw material is as follows: after the lignocellulosic raw material is crushed and impurities are removed, it is subjected to acid treatment, alkali treatment or steam explosion treatment to obtain the pretreated material.

4. The method of co-producing organic acids and lignin from lignocellulose according to claim 1, wherein, In the step two, the conditions for the acid-producing fermentation are as follows: Anaerobic 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 35-55℃; The C / N ratio is 30-60; The solid content is 2.5-15%; The fermentation time is 2-50 days.

5. The method of lignocellulose co-production of organic acids and lignin according to claim 4, characterized in that, In the step two, the conditions for the acid-producing fermentation are as follows: The pH of the acid-producing fermentation is 5-7; The temperature of the acid-producing fermentation is 37-53℃; The C / N ratio is 30-40; The solid content is 2.5-10%; The fermentation time is 7-21 days.

6. The method of lignocellulose co-production of organic acids and lignin according to claim 4, characterized in that, The nitrogen source is one or a combination of NH4Cl, corn syrup, sludge, potassium nitrate and urea.

7. The method for co-producing organic acid and lignin from lignocellulose according to claim 1, wherein, F1 stage: The running time of the F1 stage is 80-120 days; The TS value of the substrate is 4.8-5.4%; the VTS value is 4.0-4.4%; the substrate comprises a mixture of straw, kitchen waste and nitrogen source substrate; the material is fed and discharged every two days; the hydraulic retention time of the reactor is 90-110 days; wherein, TS is total solid concentration; F2 stage: The F2 stage has a running time of 50-100 days; the substrate TS is 9.8-10.5%, and the substrate VTS is 8.0-8.5%; the hydraulic retention time of the reactor is 90-110 days; The F3 stage has a running time of 120-200 days; the hydraulic retention time of the reactor is adjusted to 45-55 days; the substrate TS is 9.5-10%, and the substrate VTS is 8.0-8.6%.

8. The method for co-producing organic acid and lignin from lignocellulose according to claim 7, characterized in that, The F1 stage has a running time of 50-100 days; the substrate TS is 9.8-10.5%, and the substrate VTS is 8.0-8.5%; the hydraulic retention time of the reactor is 90-110 days; The F2 stage has a running time of 50-100 days; the substrate TS is 9.8-10.5%, and the substrate VTS is 8.0-8.5%; the hydraulic retention time of the reactor is 90-110 days; The F3 stage has a running time of 120-200 days; the hydraulic retention time of the reactor is adjusted to 45-55 days; the substrate TS is 9.5-10%, and the substrate VTS is 8.0-8.6%. The VTS ratio of the 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; the straw is steam-blasted straw; The VTS ratio of the straw, kitchen waste and nitrogen source substrate in the substrate is (0.8-1.2):(0.8-1.2):(0.8-1.2); The VTS ratio of the 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). The inoculum source comprises inocula of different sources; the inocula 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.

9. The method of lignocellulose co-production of organic acids and lignin according to claim 7, characterized in that, The cellulose anaerobic digestion sludge is selected from cellulose high-temperature anaerobic digestion sludge or cellulose mesophilic anaerobic digestion sludge; and / or, 10. The method of lignocellulose co-production of organic acids 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. The inoculum source comprises the inocula of different sources mixed according to the total solid concentration, and each sludge accounts for more than 10% of the total solid concentration.

11. The method of lignocellulose co-production of organic acids and lignin according to claim 9, characterized in that, Each sludge is mixed in equal proportions according to the total solid concentration.

12. The method of lignocellulose co-production of organic acids and lignin according to claim 11, characterized in that, The reactor is a high-temperature reactor or a mesophilic reactor.

13. The method of lignocellulose co-production of organic acids and lignin according to claim 9, characterized in that, 14. The method for co-producing organic acid and lignin from lignocellulose according to claim 13, 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℃.

15. The method for co-producing organic acid and lignin from lignocellulose according to claim 13, characterized in that, When the reactor is a high-temperature reactor, the cellulose anaerobic digestion sludge is selected from cellulose high-temperature anaerobic digestion sludge, and the glucose anaerobic digestion sludge is selected from glucose high-temperature anaerobic digestion sludge; When the reactor is a mesophilic reactor, the cellulose anaerobic digestion sludge is selected from cellulose mesophilic anaerobic digestion sludge, and the glucose anaerobic digestion sludge is selected from glucose mesophilic anaerobic digestion sludge. ​ 16. The method of lignocellulose co-production of organic acids and lignin according to claim 7, characterized in that, The inoculum source is pretreated by heat treating the inoculum source at 75-85℃ for 0.5-1.2 hours and adding a methanogenesis inhibitor to a final concentration of 4-6 mM; the methanogenesis inhibitor is selected from 2-bromoethanesulfonic acid.

17. The method of lignocellulose co-production of organic acids 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, and isovaleric acid.

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