KR20090037078A - Processes for the pretreatment of lignocellulosic biomasses by popping method, and processes for the production of saccharides and bio-ethanol using the same - Google Patents

Abstract

A pretreatment process of lignocellulosic biomasses is provided to save consumed energy and to pretreat lignocellulosic biomasses by using an environment-friendly method without the processing of the chemical substance. A pretreatment process for the hydrolysis of lignocellulosic biomasses comprises a step of popping lignocellulosic biomasses. After the biomass is submerged, the biomass is popped under the pressure of 5~25 kg/cm^2. A method for producing saccharides or bio-ethanol from lignocellulosic biomasses comprises (i) a step of performing the pretreatment by popping the lignocellulosic biomasses; and (ii) saccharifying or fermenting the pretreated biomasses.

Description

Processes for the pretreatment of lignocellulosic biomasses by popping method, and processes for the production of saccharides and bio-ethanol using the same}

The present invention relates to a pretreatment process of lignocellulosic biomasses for the production of sugar compounds and bio-ethanol, and more particularly, to the popping method. The present invention relates to a pretreatment method of lignocellulosic biomass using the present invention, and a method of producing a sugar compound and bioethanol using the same.

Lignocellulosic biomass is a leaf, stem, root, etc. of natural vegetation that breaks down or converts them into useful materials for human life, such as cellulose (cellulose, pulp), glucose, xylose, purified lignin and their induction. A large amount of ethanol, xylitol and the like can be obtained. In particular, in order to solve the greenhouse effect and petroleum depletion problem caused by global warming, much attention has been focused on the production of bio-energy using sugar compounds. Research on second generation cellulose ethanol is underway in the United States. There are two main reaction mechanisms for producing ethanol for fuel from pretreated wood-based biomass: 'saccharification' and 'fermentation'. 'Saccharification' is the process by which the cellulose component is converted into glucose by the action of an enzyme, the process by which cellulase is adsorbed on the reaction surface of cellulose to convert cellulose into cellobiose, and the cellobiose thus produced is β It can be divided into the process of conversion to glucose by the enzymatic reaction of -glucosidase (β-glucosidase). 'Fermentation' refers to a process in which glucose produced by saccharification is converted into ethanol and carbon dioxide under anaerobic conditions by microorganisms such as yeast. The biological conversion process from general biomass to ethanol is shown in FIG. 1.

The major influences on the biotechnical hydrolysis of lignocellulosic biomass include crystallinity and porosity of fibrin, and lignin or hemicellulose content also plays an important role. The lignocellulosic biomass is composed mainly of carbohydrates (cellulose and hemicellulose) and lignin, although the composition ratio varies depending on the type. Lignin has a complex three-dimensional structure of phenylpropanoid, each covalently formed with an ester bond. Hemicellulose acts as a bridge between cellulose and lignin, and the binding of hemicellulose to lignin interferes with the hydrolysis of cellulose during enzyme or acid degradation. The enzyme's adsorption capacity during biological hydrolysis using enzymes has a high correlation with the surface area of cellulose. The rate of hydrolysis increases as the amount of enzyme adsorbed increases and is determined by the crystallinity of the adsorbed enzyme and cellulose.

To date, pretreatment is known to be essential for saccharifying lignocellulosic biomass. An effective pretreatment process should be to increase the content of cellulose, decrease the crystallinity of the microfibers, and increase the enzyme adsorption per unit area of the biomass, thereby increasing the enzyme hydrolysis capacity by increasing the reactivity of the cellulose. Pretreatment methods include various physical and chemical methods, such as steam decay, alkali treatment, sulfur dioxide treatment, hydrogen peroxide treatment, supercritical ammonia treatment, weak acid extraction treatment, and ammonia free decay treatment, depending on the type of lignocellulosic biomass. Etc. are known and are actually carried out by combining these methods. Among these pretreatment methods, weak acid extraction and steam decay methods have been extensively studied. Steam decay method is a method of baking the lignocellulosic system with high pressure steam for a certain period of time and explodingly, which is less corrosive and is decomposed into relatively small pieces so that lignin can be easily dissolved. However, the steam decay method requires a high reaction temperature (around 200 to 225 ° C.), so that cellulose, which is a useful substance, is severely decomposed, and thus the yield of useful solids is low (70 to 80%, including xylan). In addition, the recovery rate of xylan, which is a useful substance produced by decomposition of hemicellulose, is also less than 65%, and has a disadvantage in that a large amount of various by-products, such as acetic acid and furfural, that are not available for recovery are generated. The weak acid extraction method is a method of pulverizing and loading wood and the like into a reactor at high temperature and high pressure (about 190 ° C.), and flowing a low concentration of acid (such as sulfuric acid) into a gap to extract and remove mainly hemicellulose and some lignin. This method equalizes the temperature in the reactor with the reaction time of the individual particles and maintains the residence time of the extracted decomposition products in the reactor, thus reducing the formation of by-products due to excessive decomposition and conversion by prolonged reactions in the high temperature state of the initial decomposition products. The recovery rate of solids (cellulose and lignin) can be increased, and the recovery rate of xylan can also be 80-90% or more. However, this method is difficult to cause physical crushing of biomass tissues such as in steam crushing, and thus the raw materials must be pulverized (about 1 mm or less), so that the fine water is accompanied by fine particles in the extract water, or the pulverization before processing There is a problem such as excessive power consumption. In addition, there is a pretreatment method using organic solvent or liquid ammonia in a similar device or using base, sulfur dioxide gas, and hydrogen peroxide as a decomposition catalyst, but the cost of chemicals is high and the cost of the equipment is increased due to the additional cost of recovery equipment. The back is pointed out as a big disadvantage, and practical application is hardly achieved except for some of special use such as pulp and paper.

As such, physical methods are generally economical due to slow processes, high energy consumption, and chemical methods are expensive due to the use of strong acids or strong alkaline compounds, unsuitable for high-volume processes, and have high toxicity and adversely affect the environment. In addition, there is an urgent need to develop an effective pretreatment method that can reduce energy consumption without causing environmental problems.

In order to solve the above-mentioned problems of the prior art, the present inventors have conducted continuous research to develop a new lignocellulosic cellulose-based biomass pretreatment method, and thus, using a popping method without chemical treatment, After developing a method for pretreatment of nocellulose-based biomass, it was confirmed that the biomaterial obtained therefrom was very effective in the saccharification process using enzymes, and thus the present invention was completed.

It is therefore an object of the present invention to provide a method for pretreatment of lignocellulosic biomass by popping.

Another object of the present invention is to provide a method for producing a sugar compound and bioethanol from lignocellulosic biomass using the pretreatment method.

First, the present invention relates to a pretreatment method for hydrolysis of lignocellulosic biomass, comprising popping lignocellulosic biomass.

Second, the present invention

1) pretreatment by popping lignocellulosic biomass;

2) saccharifying or saccharifying and fermenting the pretreated biomass:

It relates to a method for producing a sugar compound or bioethanol from lignocellulosic biomass comprising the step.

In the present invention, the biomass is preferably immersed and then popped, and is preferably popped under a pressure of 5 to 25 kg / cm 2. It is also preferable to perform saccharification using a glycosylase selected from the group consisting of glycosylase such as cellulase, xylanase, β-glucosidase and mixtures thereof. The glycosylase is preferably used in an amount of 1 to 20 parts by weight based on 100 parts by weight of the biomass, and saccharification and fermentation are preferably performed in a single reactor.

According to the present invention, it is possible to pre-treat lignocellulosic vise masses relatively simply in an environmentally friendly way without the treatment of chemicals and at the same time saving energy compared to the pretreatment methods used in the past, Biomass has been shown to be very effective for biotechnological processes using enzymes. Therefore, energy and cost input to produce bioethanol can be reduced and environmental pollution due to chemical treatment can be reduced.

Hereinafter, the present invention will be described in detail.

The present invention relates to a pretreatment method using a popping method in producing sugar compounds and bioethanol from lignocellulosic biomass. In the present invention, it is possible to use rice straw and corn straw left in the autumn as lignocellulosic biomass, but the scope of the present invention is not limited thereto. In the present invention, it is preferable to immerse rice straw and corn stalks (for example, soak it in water for a day) and then pop it. It is also preferable to pop under a pressure of 5-25 kg / cm 2, in particular 15-25 kg / cm 2. The biomass pretreated according to the present invention showed no significant difference in the content of ash, holocellulose, lignin, etc., as compared to unpretreated chemical components (see Tables 1a and 1b). However, as shown in Fig. 2, it was found that the physical and morphological changes occurred.

The saccharification process was performed by adding saccharase to the pretreated biomass, and the reduced sugar of the degradation product after saccharification was measured using DNS (3,5-dinitrosalicylic acid) method. As a result, in the case of rice straw, the untreated biomass showed a hydrolysis rate of only 0.00 to 0.07, whereas the pretreated biomass showed a high hydrolysis rate of up to 1.21. For corn cobs, the untreated biomass showed a hydrolysis rate of only 0.00 to 0.06, whereas the pretreated biomass showed high hydrolysis rates of 0.42 to 1.31 (see FIGS. 3 and 4). Therefore, the pretreatment method according to the present invention was found to be very suitable for biotechnological processes using enzymes.

The pretreatment of the biomass may be performed by acid saccharification according to a conventional method, but more preferably by enzymatic saccharification. For enzyme saccharification, preference is given to using glycosylase selected from the group consisting of, for example, cellulase, xylanase, β-glucosidase and mixtures thereof. Representatively, the glycosylase may be a mixed enzyme of cellulase and xylanase in a weight ratio of 1 to 2: 1 to 2, especially 1: 1. The glycosylase is preferably used in an amount of 1 to 20 parts by weight based on 100 parts by weight of the biomass. The saccharification process is preferably carried out at a temperature of 40 ~ 45 ℃ for 6 to 24 hours, in particular 12 to 24 hours.

In the present invention, for the production of bioethanol, the 'Separate Hydrolysis and Fermentation (SHF) process' to perform the saccharification process and the fermentation process in different reactors, and the saccharification process and fermentation process in one reactor at the same time Any of the Simultaneous Saccharification and Fermentation (SSF) processes can be used. The isolated saccharification fermentation process has the advantage that it can be reacted under the optimized conditions for enzyme and yeast respectively in the saccharification process and fermentation process, whereas the enzymatic reaction is inhibited by the intermediate and the final product cellobiose and glucose. Therefore, there is a disadvantage in that the reaction is terminated when the concentration of glucose increases as the reaction proceeds, and in order to overcome this, the amount of the enzyme must be increased so that it is not economical. In contrast, in the simultaneous saccharification fermentation process, as soon as glucose is produced during the saccharification process, the yeast can immediately remove glucose by the fermentation process and minimize the accumulation of sugar in the reactor, thereby preventing the inhibitory action of the final product in the separated saccharification fermentation process. It is possible to improve the hydrolysis reaction of the enzyme, and additionally, it is possible to reduce the device cost and reduce the cost due to the low amount of enzyme input, and there is an advantage of reducing the contamination problem because ethanol is present in the reactor. . Therefore, in the present invention, it is preferable to use a simultaneous saccharification fermentation process.

Yeast, for example Saccharomyces cerevisiae , can be used as a fermentation strain for the production of bioethanol, and the optimum temperature for saccharogenic strains and enzyme saccharification that can be fermented at high sugar concentrations is 40. Heat resistant strain capable of converting ethanol even around ~ 45 ℃, recombinant strain capable of simultaneously glycosylation and fermentation to reduce the use of expensive enzymes and high concentration of ethanol, for example, Klebsiella oxytoca P2 , may be used any of the breather Gaetano My process Custer City (Brettanomyces curstersii), saccharide as MY access probe jeureon (Saccharomyces uvzrun), known in the art such as a conventional strain Candida lash probe car (Candida brassicae) would. When the fermentation process is performed separately from the saccharification process, it is preferable to carry out for 10 to 20 hours at a temperature of 25 ~ 30 ℃, especially 29 ℃.

Hereinafter, the present invention will be described in more detail with reference to Examples, which are intended to aid the understanding of the present invention but are not intended to limit the scope of the present invention in any way.

Reference Example 1: Chemical Composition Analysis of Corn and Rice Straw

The remaining straw and cornstalks harvested in the fall were used as samples. Rice straw and corn stalks were cut to 2-3 cm after being left in the dry condition. Corn and rice straw were prepared into powder of 40-60 mesh and analyzed for chemical composition. The results of analyzing the chemical composition of rice straw are shown in Table 1a.

Example 1 Pretreatment Using Popping Method

In the autumn, 100 mg of the remaining straw and corn stalks were soaked in water for a day. Thereafter, crushing was carried out using a popping machine under a pressure of 5-25 kg / cm 2. Photographs of the appearance of the pretreated rice straw and corncob are shown in FIG. 2. In addition, the chemical composition was analyzed and the results are shown in Table 1b.

As shown in the figures and tables, the biomass pretreated using the popping machine was found to have no significant difference in the content of ash, holocellulose, lignin, etc., compared with the non-pretreated, but physically and morphologically significant changes. It appeared to cause.

Example 2: Glycosylation

50 mg of untreated (control) and crushed (experimental) rice straw and corn stalks using 1 mg of cellulase (CBDII and Cel5C), 1 mg of xylanase (XynT) and mixed enzymes (CBDII + XynT) 1 mg of Cel5C + XynT) was added, and a saccharification process was performed at a temperature of 40 ° C. for 12 hours. After saccharification, reducing sugars of rice straw and maize soybean products were measured using DNS method. The results are shown in FIGS. 3 and 4.

As shown in the figure, in the case of rice straw, the untreated ball showed only a hydrolysis rate of 0.00 to 0.07, whereas the popped experimental ball showed a high hydrolysis rate of up to 1.21. For cornstalk, the untreated plots showed only a hydrolysis rate of 0.00 to 0.06, whereas the popped experimental plots showed a high hydrolysis rate of 0.42 to 1.31. These results clearly show that the popped biomass is very suitable for biotechnological processes using enzymes.

Example 3: Production of Bioethanol

In the fall, 50 mg of the remaining straw and corn stalks were soaked in water for a day. The crushing was then carried out using a popping machine under a pressure of 21 kg / cm 2. 1 mg of cellulase (CBDII and Cel5C), 1 mg of xylanase (XynT) and 1 mg of mixed enzyme (CBDII + XynT and Cel5C + XynT) were added to the pretreated rice straw and corn stalks, respectively. 15 g / l was added to Saccharomyces cerevisiae as a fermentation strain for bioethanol production, and bioethanol was produced by performing a simultaneous saccharification fermentation process at a temperature of 29 ° C. for 15 hours.

1 is a schematic diagram showing a biological conversion process from general biomass to ethanol;

Figure 2 is a photograph showing the shape change of cornstalks and rice straw after pretreatment using a popping machine;

3 is a graph showing the change of enzyme hydrolysis rate of rice straw after pretreatment using a popping machine;

Figure 4 is a graph showing the change in enzyme hydrolysis rate of cornstalk after pretreatment using popping machine.

Claims (9)

A method of pretreatment for hydrolysis of lignocellulosic biomass, comprising popping lignocellulosic biomass. The method of claim 1, wherein the biomass is immersed and then popped. The pretreatment method according to claim 1, wherein the biomass is popped under a pressure of 5-25 kg / cm 2. 1) pretreatment by popping lignocellulosic biomass; 2) saccharifying or saccharifying and fermenting the pretreated biomass: A method for producing a sugar compound or bioethanol from lignocellulosic biomass comprising the step. The method according to claim 4, wherein the biomass is soaked in step 1) and then popped under a pressure of 5-25 kg / cm 2. The method according to claim 4 or 5, wherein the glycosylation is carried out using glycosylation enzyme in step 2). The method of claim 6, wherein the glycosylase is selected from the group consisting of cellulase, xylanase, β-glucosidase, and mixtures thereof. The method according to claim 4 or 5, wherein the glycosylase is used in step 2) in an amount of 1 to 20 parts by weight based on 100 parts by weight of the biomass. The process according to claim 4 or 5, wherein the saccharification and fermentation in step 2) are carried out in a single reactor.

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