阅读说明：本技术 密化过程中添加碱性试剂对木质纤维素进行预处理的方法 (Method for pretreating lignocellulose by adding alkaline reagent in densification process ) 是由 金明杰 陈相雪 袁鑫川 于 2019-04-08 设计创作，主要内容包括：本发明公开了一种密化过程中添加碱性试剂对木质纤维素进行预处理的方法,属于生物炼制领域。所述方法在木质纤维素原料中,加入碱性试剂或碱性溶液,混合均匀后进行密化处理,形成压缩致密形状的密化木质纤维素,然后进行酶水解和发酵。本发明通过在木质纤维素密化过程中添加碱性试剂对秸秆结构进行破坏,在木质纤维素压缩致密过程中以及在存储运输过程中实现对木质纤维素的预处理。本发明方法得到的密化木质纤维素便于储存,不易变质或腐烂,在后续处理过程中操作方便,并且预处理得到的密化木质纤维素在高底物酶水解的条件下,酶水解糖的产率达到90％以上。(The invention discloses a method for pretreating lignocellulose by adding an alkaline reagent in a densification process, and belongs to the field of biorefinery. Adding an alkaline reagent or an alkaline solution into a lignocellulose raw material, uniformly mixing, then carrying out densification treatment to form densified lignocellulose in a compressed and dense shape, and then carrying out enzymatic hydrolysis and fermentation. According to the invention, the alkaline reagent is added in the lignocellulose densification process to destroy the straw structure, so that the pretreatment of lignocellulose is realized in the lignocellulose compression and densification process and the storage and transportation process. The densified lignocellulose obtained by the method is convenient to store, is not easy to deteriorate or decay, is convenient to operate in the subsequent treatment process, and the yield of the enzyme hydrolysis sugar of the densified lignocellulose obtained by pretreatment reaches over 90 percent under the condition of high substrate enzyme hydrolysis.)

1. The method for pretreating lignocellulose by adding an alkaline reagent in the densification process is characterized by comprising the following specific steps of:

adding an alkaline reagent or an alkaline solution into a lignocellulose raw material, uniformly mixing, then carrying out densification treatment to form densified lignocellulose in a compressed compact shape, and then carrying out enzymatic hydrolysis and fermentation.

2. The method of claim 1, wherein the ligno-cellulose is selected from one or more of wheat straw, corn stover, agricultural and forestry waste, rice straw, sorghum straw, soybean stover, forestry waste, recycled wood pulp fiber, wood chips, softwood, hardwood, aquatic plants, algae, and animal manure; the moisture content of the lignocellulose is 0-90%.

3. The method of claim 1, wherein the alkaline reagent is selected from the group consisting of sodium hydroxide, calcium hydroxide, potassium hydroxide, sodium acetate, sodium carbonate, sodium bicarbonate, sodium sulfate, ethylenediamine, triethylamine, ammonia water, and liquid ammonia; the alkaline solution is calcium oxide or sodium oxide.

4. The method according to claim 1, wherein the alkaline agent is present in an amount of 0.01 to 10.0% by weight of the lignocellulose.

5. The method according to claim 1, wherein the alkaline reagent or alkaline solution is added by directly pouring or adding, spraying, introducing steam, or spraying alkaline gas, so that the alkaline reagent or alkaline solution and the lignocellulose are uniformly mixed and then subjected to lignocellulose densification treatment; or an alkaline agent or an alkaline solution is added to the densification apparatus along with the lignocellulose during the densification process.

6. The method according to claim 1, wherein the densified lignocellulose is left to stand for more than one day before being subjected to enzymatic hydrolysis.

7. The method of claim 1, wherein the densified lignocellulose is further treated prior to enzymatic hydrolysis by one or more of spraying water on the densified lignocellulose, steaming, soaking, sun exposure, low temperature freezing, high temperature treatment, microwave and ultrasonication.

8. The method of claim 1, wherein the densified lignocellulose is further pretreated prior to the enzymatic hydrolysis, wherein the further pretreatment is steam explosion pretreatment, hot water pretreatment, or hydrothermal pretreatment of steam pretreatment; or dilute strong acid pretreatment, weak acid pretreatment, oxidizing acid pretreatment and mixed acid pretreatment; or dilute strong alkali pretreatment, weak alkali pretreatment, ammonia pretreatment and oxidative alkali pretreatment or alkali pretreatment of mixed alkali pretreatment.

9. The method as claimed in claim 1, wherein the densified lignocellulose has a density of 100-³(ii) a The compressed compact shape is a rod, a granule, a block or a pill; rod-like specification: the diameter is 0.5mm-30 cm; the specification of the granules: the diameter is 0.1cm-50 cm; specification of the block shape: the length is 0.1cm-200cm, the width is 0.1cm-200cm, and the height is 0.1cm-200 cm; specification of pellet shape: the diameter is 0.1cm-50cm, and the thickness is 0.01cm-20 cm.

10. The method according to claim 1, wherein the enzymatic hydrolysis is carried out by using a hydrolytic enzyme selected from the group consisting of cellulase and/or a combination of one or more of hemicellulase, pectinase and xylanase; the fermentation microorganism adopted by the fermentation is yeast, bacteria or mould.

Technical Field

The invention belongs to the technical field of biorefinery, and relates to a method for pretreating lignocellulose by adding an alkaline reagent in a densification process.

Background

Lignocellulose is one of the most common renewable resources in nature, is widely distributed and is easy to obtain. The biological refining of the lignocellulose can not only improve the environment and meet the energy demand, but also bring considerable income for farmers due to the additional value of the lignocellulose.

The low density of loose lignocellulose makes the transportation and storage costs higher, and restricts the industrialization of lignocellulose biorefinery. Lignocellulose pretreatment is an essential step in the process of producing target products such as biofuel by biorefinery, and the function of the pretreatment is to reduce the natural resistance of lignocellulose and facilitate the enzymatic hydrolysis. The traditional pretreatment method has the problems of serious corrosion to the pretreatment reaction instrument, low safety, high energy consumption, troublesome operation and the like (Thereraratananon K, XuF, Wilson J, et al. effects of the pelletting conditions on chemical composition and sub-yield of corn stock, big blue, while strain, and sorghum stalkseeds [ J ] Bioprocess biosystem Eng,2012,35(4):615 and 623). In addition, the loose lignocellulose limits the loading of pretreatment and enzyme hydrolysis, reduces the strength of industrial production of the lignocellulose, limits the concentration of target products of enzyme hydrolysis and fermentation, and increases the extraction cost of the target products.

The density of the lignocellulose can be effectively increased (the density can be increased by 5-15 times) by compacting the lignocellulose into a compact structure. The storage cost and the transportation cost of the compact lignocellulose can be respectively reduced by more than 50 percent and 90 percent. In addition, the dense lignocelluloses all have uniform size and shape, facilitating the operation of industrial production (Zhang P F, Zhang Q, Deines T W, et al. ultrasonic Vibration-Assisted Pelleting of Wheat Straw: A design Experimenton investment on Pellet Quality and Sugar Yield, American Industrial Manufacturing Science & Engineering conference.2012). After pretreatment, the densified lignocellulose is beneficial to improving the concentration of a substrate without a batch feeding process. The densified lignocellulose retains a large amount of free water due to the compact structure, which is beneficial to the hydrolysis of the lignocellulose by enzyme. The Bryan D.Bals study found that after AFEX pretreatment, densified corn stover was hydrolyzed with 18% substrate enzyme, and after 72 hours, the yield of glucose reached 68% and xylose was 65%, which was 3% higher than the yield of sugar after enzymatic hydrolysis of loose stover under the same conditions (Bals B D, Gunawan C, Moore J, et al. enzymetic hydrolysis of pelleted XTM-threaded corn high dissolved feeding, Biotechnology and Bioengineering,2014,111(2): 264-.

Densification of lignocellulose, while beneficial in increasing the feedstock loading during pretreatment, also results in increased pretreatment conditions, such as increased temperature and extended reaction time. Meanwhile, the densified lignocellulose and the solution containing the chemical reagent cannot fully react in the pretreatment process, and the solution cannot permeate into the solution due to the compact lignocellulose structure, so that the pretreated lignocellulose is uneven, and more byproducts are generated. As the pretreatment temperature increases, the difference in temperature between the inside and outside of the densified lignocellulose may also affect the pretreatment effect.

Disclosure of Invention

Aiming at the problems of high transportation cost, high pretreatment energy consumption and the like of the existing lignocellulose, the invention provides a method for pretreating the lignocellulose by adding an alkaline reagent in the densification process, and the lignocellulose is pretreated by adding the alkaline reagent in the densification process of the lignocellulose.

The technical scheme of the invention is as follows:

the method for pretreating lignocellulose by adding an alkaline reagent in the densification process comprises the following specific steps:

adding an alkaline reagent or an alkaline solution into a lignocellulose raw material, uniformly mixing, then carrying out densification treatment to form densified lignocellulose in a compressed compact shape, and then carrying out enzymatic hydrolysis and fermentation.

In the invention, the lignocellulose is selected from one or more of wheat straw, corn straw, agriculture and forestry waste, rice straw, sorghum straw, soybean straw, forestry waste, recycled wood pulp fiber, wood chips, softwood, hardwood, aquatic plants, algae and animal manure; the moisture content of the lignocellulose is 0-90%.

In the invention, the alkaline reagent can be sodium hydroxide, calcium hydroxide, potassium hydroxide, sodium acetate, sodium carbonate, sodium bicarbonate, sodium sulfate, ethylenediamine, triethylamine, ammonia water or liquid ammonia; the alkaline solution may be calcium oxide or sodium oxide.

In the invention, the alkaline reagent accounts for 0.01-10.0% of the mass of the lignocellulose.

In the invention, the adding mode of the alkaline reagent or the alkaline solution can be directly pouring or adding, spraying, introducing steam, spraying alkaline gas and the like, so that the alkaline reagent or the alkaline solution and the lignocellulose are uniformly mixed and then are subjected to lignocellulose densification treatment, or the alkaline reagent or the alkaline solution and the lignocellulose are added into a densification instrument together in the densification process.

In a preferred embodiment of the present invention, the densified lignocellulose may be left to stand for at least one day before being subjected to enzymatic hydrolysis.

As a preferable scheme of the invention, the densified lignocellulose is further treated before the enzymatic hydrolysis, and the treatment can be one or more of water spraying, steam introducing, soaking, insolation, low-temperature freezing, high-temperature treatment, microwave and ultrasonic crushing on the surface of the densified lignocellulose;

as a preferred embodiment of the present invention, before the enzymatic hydrolysis, the densified lignocellulose is further pretreated, and the further pretreatment may be hydrothermal pretreatment, including steam explosion pretreatment, hot water pretreatment, and steam pretreatment; acid pretreatment; acid pretreatment, including dilute strong acid pretreatment, weak acid pretreatment, oxidizing acid pretreatment and mixed acid pretreatment; and alkaline pretreatment, including dilute strong alkali pretreatment, weak alkali pretreatment, ammonia pretreatment, oxidizing alkali pretreatment and mixed alkali pretreatment.

In the invention, the compressed compact shape is a compressed compact shape prepared by conventional biological refining and can be a compact structure shape such as a rod, a granule, a block, a pellet and the like.

In the invention, the density of the densified lignocellulose is 100-1500kg/m³The rod-shaped specification: the diameter is 0.5mm-30 cm; the specification of the granules: the diameter is 0.1cm-50 cm; specification of the block shape: the length is 0.1cm-200cm, the width is 0.1cm-200cm, and the height is 0.1cm-200 cm; specification of pellet shape: the diameter is 0.1cm-50cm, and the thickness is 0.01cm-20 cm.

In the invention, the hydrolase used for the enzymatic hydrolysis is a hydrolase used in conventional biorefineries, and can be cellulase and/or a combination of one or more of hemicellulase, pectinase and xylanase.

In the invention, the fermentation microorganism adopted by the fermentation is a fermentation microorganism used in conventional biorefinery, and can be yeast, bacteria or mould.

According to the invention, the alkaline reagent is added in the densification process of the lignocellulose, so that the mechanical action in the densification process and the heat in the compression process are utilized to destroy the structure of the lignocellulose, and the alkaline reagent can play a chemical role in the lignocellulose in the transportation and storage processes at-40-100 ℃, so that the lignocellulose is pretreated, and then the lignocellulose can be directly used for the next step of enzymatic hydrolysis and fermentation, or further pretreatment is carried out (the alkaline reagent is fully mixed with the lignocellulose at the moment, so that the further pretreatment can be carried out under the condition of high lignocellulose loading capacity), and then the enzymatic hydrolysis and fermentation are carried out.

Compared with the prior pretreatment technology, the invention has the following advantages:

(1) the lignocellulose is physically crushed in the densification process, so that the lignocellulose and the chemical reagent are uniformly mixed and fully reacted, the pretreatment is realized in the densification, storage and transportation processes, and the pretreatment cost is greatly saved;

(2) the densified lignocellulose obtained by the method is convenient to store, is not easy to deteriorate or decay, and is convenient to operate in the subsequent treatment process;

(3) the densified lignocellulose improves the loading of pretreatment and enzyme hydrolysis, and the yield of the enzyme hydrolysis sugar reaches over 90 percent under the condition of high substrate enzyme hydrolysis.

Drawings

FIG. 1 is a graph of the straw surface change of corn stover at different storage times after densification in example 1 with and without an alkaline agent.

FIG. 2 is a comparison of the enzymatic hydrolysis effect of alkali-densified corn stover and dilute alkali-pretreated densified corn stover from the hot water pretreatment of example 2. A: hot water pretreatment of alkali-containing densified corn straws is carried out for 10 minutes at the temperature of 121 ℃; b: the dense straw is pretreated by dilute alkali at the temperature of 121 ℃ for 20 minutes.

FIG. 3 is a graph of the effect of calcium hydroxide solution on enzymatic hydrolysis on different days of storage after the addition of calcium hydroxide solution to densify corn stover (15% calcium hydroxide addition based on dry weight of corn stover) in example 3.

FIG. 4 is a graph of the effect of example 4 on enzymatic hydrolysis on different days of storage after the addition of sodium hydroxide solution to densify corn stover (calcium hydroxide is added at 30% of the dry weight of the corn stover).

Detailed Description

In order to facilitate understanding of the invention, the invention will be described more fully and in detail with reference to the accompanying drawings and preferred embodiments, but the scope of the invention is not limited to the specific embodiments described below.

All terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art, unless otherwise defined. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.

Unless otherwise specifically stated, reagents, starting materials, instruments, equipment and the like used in the present invention are commercially available or prepared by an existing method.