阅读说明：本技术 一种使用生物可降解有机酸催化剂的木质纤维素预处理方法 (Lignocellulose pretreatment method using biodegradable organic acid catalyst ) 是由 鲍杰 张斌 郑理想 于 2019-10-29 设计创作，主要内容包括：本发明涉及到一种使用生物可降解有机酸催化剂的木质纤维素预处理方法,以及有机酸催化剂的完全生物降解方法。具体步骤为：(1)配置5～10％(w/v)的草酸溶液；(2)木质纤维素物料与草酸溶液以1:2-3:1的高固液比在预处理反应器中均匀混合；(3)在预处理反应器中喷射低压蒸汽；(4)对草酸及预处理过程中产生的抑制物使用特定微生物菌株进行生物降解。最终预处理物料中有机酸催化剂及抑制物无残余,物料含水量不超过60％,呈干固颗粒状,无游离废水产生。本发明固态草酸的运输、储存以及使用的安全性更高；高固液比实现过程中游离废水的零排放和蒸汽低用量；同时也基本排除了木质素残渣焚烧过程中的二氧化硫排放问题。(The present invention relates to a method for pretreating lignocellulose using a biodegradable organic acid catalyst, and a method for completely biodegrading an organic acid catalyst. The method comprises the following specific steps: (1) preparing 5-10% (w/v) oxalic acid solution; (2) uniformly mixing the lignocellulose material and oxalic acid solution in a pretreatment reactor at a high solid-to-liquid ratio of 1:2-3: 1; (3) injecting low pressure steam in the pretreatment reactor; (4) the oxalic acid and the inhibitor generated in the pretreatment process are biodegraded by using a specific microorganism strain. The organic acid catalyst and inhibitor in the final pretreated material have no residue, the water content of the material is not more than 60 percent, the material is in a dry solid granular shape, and no free wastewater is generated. The solid oxalic acid has higher safety in transportation, storage and use; the high solid-liquid ratio realizes zero discharge of free wastewater and low steam consumption in the process; meanwhile, the problem of sulfur dioxide emission in the process of burning the lignin residues is basically solved.)

1. A lignocellulose pretreatment method using a biodegradable organic acid catalyst is characterized by comprising the following steps:

(1) preparing 5-10% (w/v) oxalic acid solution;

(2) stirring and uniformly mixing the crushed and cleaned lignocellulose raw material and an oxalic acid solution in a pretreatment reactor according to a high solid-to-liquid mass ratio of 1:2-3: 1;

(3) injecting low-pressure steam in the pretreatment reactor and keeping the low-pressure steam for a certain time;

(4) continuing to biodegrade the product obtained in the step (3), and biodegrading oxalic acid and inhibitors generated in the pretreatment process by using a specific microbial strain under the conditions of low pH and no loss of fermentable sugar;

the biodegradation process is solid state fermentation, the used bacterial strain can effectively degrade oxalic acid and inhibitor in the acidic environment of the pretreated material, the bacterial strain is Paecilomyces variotii FN89(Paecilomyces variotii FN89), the preservation number is CGMCC17665, the preservation date is 2019, 5 and 8 days, and the preservation address is the China general microbiological culture Collection center of China microbiological culture Collection center in the sunward area of Beijing;

(5) the final material can be directly fed into the subsequent high solid content biological processing process.

2. The method for pre-treating lignocellulose using a biodegradable organic acid catalyst as recited in claim 1, wherein in the step (2), the lignocellulose raw material includes but is not limited to one or more of agricultural wastes such as corn stover, wheat straw, cotton stalk, sesame stalk, rape stalk, sweet sorghum stalk, corn cob, rice hull, rice husk, bagasse, rice straw, wood chips, hardwood and softwood.

3. The method for pretreating lignocellulose using a biodegradable organic acid catalyst according to claim 1, wherein the volume of the pretreatment reactor in step (2) is 20-50L, the stirring speed is 50-100rpm, and the stirring time is 3-5 min.

4. The method for pretreating lignocellulose using a biodegradable organic acid catalyst according to claim 1, wherein in the step (3), low-pressure steam is injected, 0.5MPa < steam pressure <1.6MPa, 158 ℃ < steam temperature <201 ℃.

5. The method for pretreating lignocellulose using a biodegradable organic acid catalyst as recited in claim 1, wherein in the step (3), the reaction conditions are kept at 165-195 ℃ for 3-10 min.

6. The method for pretreating lignocellulose using a biodegradable organic acid catalyst according to claim 1, wherein in the step (3), the material completely absorbs the acid solution without generating any free wastewater.

7. The method for pretreating lignocellulose using a biodegradable organic acid catalyst according to claim 1, wherein in the step (4), the temperature of the biodegradation process is 28-30 ℃, the inoculation amount is 10-20%, the ventilation amount is 0.5-1vvm, the stirring is performed at 50-100rpm every 12-24h for 3-5min, and the culture time is 48-72 h.

8. The method for pretreating lignocellulose using a biodegradable organic acid catalyst according to claim 1, wherein in the step (5), the final material contains no more than 60% of water and is in a dry solid granular form, and the organic acid catalyst and the inhibitor have no residue.

9. The method for pretreating lignocellulose according to claim 1, wherein in the step (5), the high-solid-content biological processes including microbial ethanol production, microbial oil production, microbial amino acid production and other biorefineries using biodegradable organic acid-pretreated lignocellulose as a substrate.

Technical Field

The invention relates to the field of chemical industry and biological energy, in particular to a zero-wastewater-discharge lignocellulose pretreatment method by using a degradable organic acid catalyst.

Background

Lignocellulose is a widely distributed renewable resource with huge reserves, and can be used for producing various energy sources and products with high added values by a biorefinery technology. The main components of lignocellulose include cellulose, hemicellulose, and lignin. The inherent structure of lignocellulose can be broken through an effective pretreatment means, the wrapping of lignin and hemicellulose on the cellulose is eliminated, the contact area of cellulase and the cellulose is increased, and then the subsequent enzymolysis efficiency and the conversion efficiency of biological fermentation can be effectively improved. Effective pretreatment techniques are therefore of great importance for biorefineries that use lignocellulose as a feedstock.

The main lignocellulose pretreatment methods comprise a dilute sulfuric acid method, a sulfur dioxide method, ammonia fiber expansion and explosion and steam expansion and explosion technologies, and the technologies are proved to be capable of effectively breaking the original biological structure of the lignocellulose raw material and improving the subsequent enzymolysis efficiency. Wherein the dilute sulfuric acid method is applied to a part of the industrial demonstration devices of the cellulose ethanol. The conventional dilute sulfuric acid method pretreatment technology is to adopt sulfuric acid as a pretreatment catalyst, mix a dilute sulfuric acid solution with a certain concentration and a lignocellulose raw material in a very high ratio (about 10: 1-20: 1), and maintain a certain reaction time under the conditions of high temperature and high pressure to obtain a pretreated product. However, although the conventional dilute sulfuric acid pretreatment technology can effectively hydrolyze hemicellulose, destroy the crystalline structure of cellulose and partially depolymerize lignin, the following problems still exist in the application process:

due to high corrosivity and high oxidizability, the sulfuric acid has extremely high requirements on the corrosion resistance and safety of equipment in the processes of transportation, storage and use.

Secondly, neutralizing a sulfuric acid catalyst adsorbed by the pretreated material, and finally accumulating calcium salt precipitates generated by using calcium hydroxide as a neutralizing agent in lignin residues; when the lignin residues are used for steam production or power generation incineration, a large amount of sulfur dioxide is discharged;

thirdly, when ammonia water or sodium hydroxide is used for neutralizing the sulfuric acid catalyst adsorbed by the pretreated material, high-concentration ammonium salt or sodium salt can be generated, and the treatment cost of the subsequent process is greatly increased;

and (IV) the conventional dilute sulfuric acid pretreatment process requires extremely large water quantity, the energy consumption for heating and boosting the high water quantity is huge, and the pollution treatment cost is aggravated by subsequent large-amount sewage discharge.

And (V) the use of a large amount of acid solution leads to the solid content of the pretreatment product to be generally lower than 10% (w/w), and the pretreatment product can be recovered for subsequent enzymolysis and microbial fermentation only by solid-liquid separation, thereby increasing the operation and equipment cost.

And (V) various inhibitors for inhibiting subsequent enzymolysis and microbial growth are formed due to excessive degradation in the pretreatment process, and further treatment is needed.

The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

Disclosure of Invention

In view of the above-mentioned deficiencies of conventional dilute acid pretreatment techniques for lignocellulose, the present invention provides a method for pretreating lignocellulose using a biodegradable organic acid catalyst. On the premise of ensuring the pretreatment strength, the safety of the method is improved, the pollution, the energy consumption and the production cost are reduced, the obtained pretreatment product can be efficiently and simply used for the subsequent high-solid-content biological processing process, the production process is simplified, and the method has great industrial application potential.

In order to achieve the purpose, the invention is realized by the following technical scheme:

a lignocellulose pretreatment method using degradable organic acid catalyst and zero wastewater discharge comprises the following specific steps:

(1) preparing 5-10% (w/v) oxalic acid solution.

(2) The crushed and clean lignocellulose raw material and oxalic acid solution are uniformly stirred in a pretreatment reactor according to a high solid-to-liquid ratio.

The lignocellulosic feedstock includes, but is not limited to, one or more of agricultural wastes such as corn stover, wheat straw, cotton stalks, sesame stalks, canola stalks, sweet sorghum stalks, corn cobs, rice hulls, bagasse, rice straw, wood chips, hardwood, and softwood.

The high solid-liquid ratio is 1:2-3:1, wherein the best effect is achieved when the solid-liquid ratio is 2: 1.

The volume of the pretreatment reactor is 20-50L, the stirring speed is 50-100rpm, and the stirring time is 3-5 min.

(3) Low pressure steam is injected in the pretreatment reactor and maintained for a certain period of time.

The steam pressure of the low-pressure steam sprayed is more than 0.5MPa and less than 1.6MPa, and the steam temperature is more than 158 ℃ and less than 201 ℃. The reaction conditions were kept at 165-195 ℃ for 3-10 min.

In the pretreatment reaction process, the materials completely absorb the acid solution, and no free wastewater is generated.

(4) And (4) continuing to biodegrade the product obtained in the step (3), and biodegrading oxalic acid and an inhibitor generated in the pretreatment process by using a specific microbial strain under the conditions of low pH and no loss of fermentable sugar.

The temperature of the biodegradation process is 28-30 ℃, and the inoculation amount is 10-20%.

The biodegradation process is solid state fermentation, the used bacterial strain can effectively degrade oxalic acid and inhibitor in the acidic environment of the pretreated material, the bacterial strain is Paecilomyces variotii FN89(Paecilomyces variotii FN89), the preservation number is CGMCC No.17665, the preservation date is 5-8 days in 2019, and the preservation address is as follows: xilu No.1 Hospital No. 3, Beijing, Chaoyang, North; the name of the depository: china general microbiological culture Collection center. The fermentation conditions are that the temperature is 28-30 ℃, the ventilation volume is 0.5-1vvm, the stirring is carried out for 3-5min at the rotating speed of 50-100rpm every 12-24h, and the culture time is 48-72 h.

(5) The final material can be directly fed into the subsequent high solid content biological processing process.

The water content of the final material is not more than 60%, the final material is in a dry solid granular shape, and the organic acid catalyst and the inhibitor have no residues.

The high solid content biological processing process comprises all biological refining processes which take lignocellulose pretreated by biodegradable organic acid as a substrate, such as microbial ethanol production, microbial oil production, microbial amino acid production and the like.

In the present invention, the degradable organic acid catalyst used is oxalic acid. Oxalic acid is the simplest dicarboxylic acid and can be prepared from biomass-derived carbohydrates or carbon monoxide as starting materials. The method can be used for pretreating lignocellulose under the condition of extremely high solid content, the pretreated material is in a dry solid granular state, no free wastewater is generated, and the steam energy consumption is extremely low. The pretreated oxalic acid can be completely degraded into carbon dioxide and water by microorganisms. The method not only avoids the subsequent treatment problem of calcium salt precipitate or high-concentration soluble salt generated by the neutralization of the inorganic acid catalyst in the conventional pretreatment technology, but also avoids the discharge of a large amount of wastewater in the conventional pretreatment process.

Compared with the prior dilute acid pretreatment technology, the method has the following beneficial effects:

the safety of transportation, storage and use of the solid oxalic acid is higher;

the acid catalyst does not need to be neutralized, the complete biodegradation of the organic acid catalyst and the inhibitor can be realized under the condition of low pH, and the subsequent enzymolysis and microbial fermentation efficiency is improved; the pollution and the operation flow are reduced;

thirdly, the concentration of sulfur ions in the lignin residues is greatly reduced, and the emission of sulfur dioxide generated after the lignin residues are used for steam generation and power generation incineration is controlled;

fourthly, the extremely high solid-liquid ratio is adopted, so that the water requirement in the pretreatment process is less, the energy consumption required by the heating and boosting operation is reduced, and the zero discharge of free wastewater is realized;

(V) the final material has a water content of no more than 60%, is in a dry solid granular shape, has no residue of an organic acid catalyst and an inhibitor, and can directly enter a high-solid-content biological processing process, so that the production continuity is ensured; simplifies the production process and reduces the production cost.

Detailed Description

The present invention will be described in further detail with reference to examples, but the embodiments of the present invention are not limited to the scope of the examples.