Medicine and other fields, it can also partially or completely replace gasoline, which is safe and clean.
Clean, renewable and other advantages. Traditional alcohol production mainly consists of molasses, potatoes and grains.
It is fermented from raw materials. In recent years, with the population growth and economic development.
The decrease of arable land makes the cost of alcohol production increase day by day, and the utilization of alcohol
It has become an inevitable trend to use abundant and cheap corn stalks to produce alcohol. I
China is a big agricultural country, with abundant cellulose raw material resources, only corn.
The annual output of straw is about 200 million tons. At present, except for a small number of corn stalks.
Most of them are directly dumped into the environment in the form of accumulation and incineration, which greatly pollutes the environment.
The environment is also a waste of resources. If the corn stalks are pretreated
Hydrolysis, in which cellulose and hemicellulose can be decomposed into sugar, and sugar can be transformed by fermentation.
When converted into alcohol, the thermal efficiency can reach more than 30%. This will not only ease people's faces.
Facing a series of problems such as food shortage, environmental pollution and resource crisis, and
It can realize the sustainable development of human beings, so in recent years, corn straw has become a living thing.
Research hotspots in the field of energy.
1 Brief Introduction of Corn Stalk
Corn stalk is mainly composed of plant cell walls, and the basic component is cellulose.
Hemicellulose and lignin, etc. Lignin wraps cellulose and hemicellulose layer by layer.
Wai. Cellulose is a kind of linear polysaccharide, and many molecules are arranged in parallel to form filamentous insolubility.
Sex microfiber, hemicellulose is mainly composed of xylose, a small amount of arabinose, galactose,
Mannose, lignin is composed of phenylpropane and its derivatives as the basic unit.
Polymer aromatic compounds. Among them, lignin is a fuel, semi-fiber.
Vegetables can be hydrolyzed into five-carbon sugars, while cellulose is more difficult to be hydrolyzed into six-carbon sugars.
2 Pretreatment of corn stalk
Because of the complex structure of corn stalk, wood is not only covered with cellulose and hemicellulose.
Element package, the valence of hemicellulose is combined with lignin, and cellulose
Has a highly ordered crystal structure. Therefore, it must be pretreated to make fibers.
The separation of lignin, hemicellulose and lignin cut off their hydrogen bonds and destroyed the crystal knot.
Structure, reduce the degree of polymerization. Common pretreatment methods include physical method, chemical method and physical method.
Chemical method and microbial method.
2. 1 extrusion expansion method
This method belongs to physical treatment, that is, raw materials are crushed and adjusted to a certain extent.
Water is added to the extruder, and the material moves forward under the rotation of the screw.
Simultaneously cutting and extruding. Under the action of friction heat, the temperature will approach.
140℃; Then it is ejected from the extruder, and the pressure of the material suddenly decreases and the volume is fast.
Rapid expansion destroys the crystal structure of cellulose, which is the enzymatic treatment of cellulose.
Create conditions. This pretreatment method has a continuous production process and does not need to consume steam.
Steam, and has a bactericidal effect.
2.2 Wet oxidation method
Wet oxidation is a chemical treatment method, that is, water is heated and pressurized.
And oxygen participate in the reaction. Wet oxidation is very effective for treating corn stalks.
Well, when cellulose meets alkali, it will only cause cellulose to swell to form alkalized cellulose, but
Can keep the original skeleton, and can prevent fiber after adding Na2CO3.
Elements are destroyed, so that lignin and hemicellulose are dissolved in alkaline solution and react with cellulose.
Separation. The cellulose thus obtained has high purity and few by-products. Hungary
Eniko et al. at 195℃,15min, 1 200 kPa O2,
Under the condition of Na2CO32g/L, 60g/L corn stalk was pretreated. In ...
60% hemicellulose and 30% lignin are dissolved, and 90% cellulose is separated in solid state.
In recent years, the enzymatic conversion rate (ECC) of cellulose has reached about 85%.
2.3 acid treatment method
Acid treatment is also a chemical treatment, which can be traced back to.
1980, and Germany may be earlier. The method adopts sulfuric acid, nitric acid, hydrochloric acid,
Phosphoric acid is used to pretreat cellulose raw materials, and sulfuric acid is used for research and application.
Most. After treatment, hemicellulose is hydrolyzed to obtain carbon-free sugar and cellulose.
The crystal structure is destroyed, the raw materials are loose and the fermentation is strong. But before hydrolysis, it must be
When the pH value is adjusted to neutral, we should also pay attention to the acid resistance of the reactor.
2.4 steam blasting method
Steam explosion method belongs to physical treatment chemical method, which uses steam to add raw materials.
Heat to 180 ~ 200℃ for 5 ~ 30 minutes, or heat to 245℃ for curing.
0.5 ~ 2.0 minutes. High temperature and high pressure soften lignin, and then quickly make it into raw materials.
Decompression causes the rupture of cellulose crystals and fiber bundles, which makes lignin and cellulose
Separation. This method is costly, and Lai Wenheng's teaching of Beijing Forestry University can be adopted in China.
Intermittent steam blaster is used to blast corn stalks.
The hydrolysis conversion rate of corn stalk cellulose after blasting with this blaster can reach 90%.
More than 70%.
2.5 Biological methods
Biological treatment can save chemical raw materials and energy and reduce environmental pollution.
Dyeing and other advantages. There are many microorganisms that can produce ligninolytic enzymes, such as white.
Rot bacteria have strong ability to decompose lignin, but their activity is low, and microorganisms
If the treatment time is long, bacteria will destroy some cellulose and hemicellulose and reduce fiber.
The hydrolysis rate of pigment is difficult to be utilized. Nordic countries such as Sweden do not use it.
Wherein basidiomycete mutants of cellulase delignify cellulose materials.
Reasons, and achieved certain results.
Research status and prospect of corn stalk fermentation to produce fuel alcohol
Wu Xiuqin 1, 2 Ma Canling 3
(1 Tianjin university of science and technology, Tianjin, China 300222; Department of Environmental Engineering; Henan Polytechnic University; Department of Biology, Zhengzhou Normal University)
Corn stalk is a rich renewable resource, which is mainly composed of cellulose, hemicellulose and lignin. Alcohol can be produced by pretreatment, hydrolysis and fermentation. Pretreatment methods mainly
There are physical methods, chemical methods, physical and chemical methods and biological treatment methods; Hydrolysis mainly includes acid hydrolysis and enzyme hydrolysis; Fermentation mainly includes direct fermentation, indirect fermentation, synchronous saccharification fermentation and so on.
The key technology progress of ethanol production from corn stalk was introduced.
Straw; Alcohol; Pretreatment; research progress
China Library Classification. TS262.2 document id number a1007-5739 (2008)13-0240-02.
Date of receipt: May 7, 2008
240 Modern Agricultural Science and Technology,No. 13, 2008
3 Hydrolysis process
After pretreatment of corn stalk, cellulose hydrolysis can only be carried out in the presence of catalyst.
It can only be carried out under the following circumstances. Commonly used catalysts are inorganic acids and enzymes, so
Acid hydrolysis process and enzyme hydrolysis process are respectively formed, and acid hydrolysis process is divided into
Dilute acid hydrolysis and concentrated acid hydrolysis. Hydrolysis mainly destroys cellulose and hemicellulose.
Hydrogen bonds make it a fermented monosaccharide.
3. 1 concentrated acid hydrolysis
React with 70% sulfuric acid at 50℃ for 2 ~ 6 hours in a reactor, hemicellulose.
The first is degradation, and after several times of concentration and drainage, water-soluble substances are obtained.
After dehydration, the solid residue of sugar and hemicellulose is 30% ~ 40%.
Soak in sulfuric acid 1 ~ 4h. After dehydration and drying, the solution was treated with 70% sulfuric acid.
Reaction 1 ~ 4 hours, the recovered sugar and acid solution are ion-exchanged, and the separated acid is in
Concentrating again in a high-efficiency evaporator, and recycling the remaining solid residues to
In the next hydrolysis. The main advantage of concentrated acid hydrolysis process is the recovery rate of sugar
High, about 90% of hemicellulose and cellulose invert sugar are recovered. dense
Sulfuric acid is corrosive, so it is necessary to recover concentrated sulfuric acid from the economic point of view.
The complexity of this process is discussed.
3.2 Dilute acid hydrolysis
In order to solve the problems existing in concentrated acid hydrolysis, dilute sulfuric acid is generally used.
(0.2% ~ 0.5%) under mild conditions. At this time, hydrolysis is generally divided into two parts.
Stage: 1 stage is low temperature operation, and the maximum sugar yield is obtained from hemicellulose;
In the second stage, cellulose is hydrolyzed into hexose and converted into sugar by high temperature operation.
The ratio is generally around 50%. However, dilute acid hydrolysis is easy to produce a large number of by-products.
3.3 Enzymatic hydrolysis
Enzymatic hydrolysis is made by microorganisms or cellulases that produce cellulase.
The product directly hydrolyzes hemicellulose and cellulose into fermentable sugar. Acid hydrolysis stage
It can be carried out under normal pressure, with mild reaction conditions, high efficiency, low energy consumption and good selectivity.
Strong selectivity, good environmental protection effect and good application value and prospect. hydrolyze
After that, a single product can be formed with high yield (>: 95%). Eniko, Hungary etc.
NovoYm 188 was used to hydrolyze corn stalks after wet oxidation and hydrolyze fibers.
The conversion rate (ECC) is as high as 85%.
The key of this method lies in the acquisition and utilization of cellulase, and at the same time, it should be considered
The cost of cellulase. Novozymes Denmark has announced the production of cellulase.
The production cost has been reduced by 12 times, and now the company has made great progress.
Development, the production cost of cellulase is 20 times lower than the original, and lL fuel is produced.
The cost of cellulase needed for primary ethanol has been less than 6.6 cents. This is a great progress.
The commercialization process of fuel ethanol is introduced.
4 Fermentation process
Because a considerable part of crop straw is composed of hemicellulose, it is hydrolyzed.
The product is five-carbon sugar with xylose as the main component, and a considerable amount of arabinose is produced.
(it can account for 10% ~ 20% of pentose), so it determines the fermentation efficiency of pentose.
An important factor of project economy. The existence of xylose inhibited the hydrolysis of cellulase.
Effect of timely conversion of xylose to ethanol on efficient ethanol production from corn stalk.
Yeast is very important. At present, people study the most and have the most industrial application prospects.
There are three kinds of yeast strains that produce ethanol by xylose fermentation, namely yeast,
The main fermentation methods of Pichia pastoris and Candida hatha are as follows.
Several kinds.
4. 1 direct fermentation method
The direct fermentation method is based on the direct fermentation of cellulose by cellulose-decomposing bacteria.
Ethanol does not need to be pretreated by acid hydrolysis or enzyme hydrolysis. Universal mixing
Direct fermentation of combined bacteria, such as Clostridium thermophilus.
Cellulose is decomposed, but the yield of ethanol is low (50%), and Clostridium thermosulfide (Col-
Stridium thermohydz) can't use cellulose, but the ethanol production is quite high.
If mixed fermentation is carried out, the yield can reach 70%. Lu introduced Clostridium thermocellum.
Research progress on physiological and biochemical characteristics and fermentation production of Clostridium thermocellum
Factors of ethanol production by fermentation and the inhibitory effect of ethanol and other fermentation products on Clostridium thermocellum
Function summary. However, the ethanol produced by Clostridium thermocellum also has the following problems: fermentation
Incomplete, the fermentation speed is slow, and the final products ethanol and organic acids have considerable influence on cells.
Toxicity needs to be further improved.
4.2 indirect fermentation method
Indirect fermentation is one of the most studied methods at present. Use cellulase
Hydrolyzing cellulose, collecting the sugar solution after enzymolysis as a carbon source for yeast fermentation, firstly utilizing
Cellulase hydrolyzes cellulose, and the sugar solution after enzymolysis is used as the fermentation carbon source. But subject to
The inhibition of end products, low cell concentration and substrate matrix affect B.
Alcohol production. Therefore, the methods that can be used are: reduced pressure fermentation and α-Laval method.
The company's biological methods can also survive at high sugar concentrations.
Overcoming matrix inhibition by mutant strains of high-sugar microorganisms.
4.3 Synchronous saccharification and fermentation method (SSF method)
The principle of this method, like indirect fermentation, is to overcome feedback.
The inhibition proposed by Gauss and others is the same as saccharification and fermentation in the same reactor.
Step by step. In this way, the enzymatic hydrolysis and fermentation saccharification of cellulose by cellulase are completed.
Continuously in the same device. Glucose hydrolysate is due to the continuous growth of bacteria.
With fermentation, this eliminates the reaction of glucose to cellulase due to substrate concentration.
Feedback suppression. The process adopts one-step fermentation, which simplifies the equipment and saves money.
The total production time is shortened and the production efficiency is improved. Of course, there are also some inhibiting factors.
The inhibitory factors such as xylose, saccharification and fermentation temperature are not harmonious. Zhang Jiquan is here.
A lot of experimental research has been done in this field, and some progress has been made.
4.4 Immobilized Cell Fermentation
Immobilized cell fermentation can increase the cell concentration in the fermentor, and the cells can
Continuous use can improve the alcohol concentration of the final fermentation broth. Common braking
The carrier includes sodium alginate, carrageenan, porous glass, etc. New Movement of Immobilized Cells
Fermentation to mixed fixed cells, such as yeast immobilized with cellobiase.
Converting cellobiose matrix into ethanol is considered to be the production of ethanol from corn straw.
An important method.
5 Conclusion and prospect
In the future, the research direction of ethanol production from corn straw will mainly focus on
The next few aspects.
5. 1 Pretreatment method
Simple physical and chemical methods are not enough to destroy the crystal structure of cellulose.
To remove hemicellulose and lignin, physical and chemical methods should be used comprehensively.
Pretreatment and hydrolysis are completed in two steps, which effectively improves the hydrolysis rate of cellulose.
5.2 Saccharification process
Alcohol production in fermentation process is influenced by many factors, among which water is the main factor.
Hydrolysis efficiency and monosaccharide yield. Comparatively speaking, enzymatic hydrolysis is better than acid hydrolysis.
Evolution will become the main development direction of saccharification technology in the future.
(Continued to page 243)
Field agronomy
24 1 modern agricultural science and technology, No.2008 13.
Area, production of high-quality and high-yield cultivation typical, excellent varieties, production technology
Transfer technology to farmers, improve production level, and consciously implement production operation procedures.
Cheng. To this end, the research group asked all counties (cities) to pay close attention to the construction of the park for a total of three years.
A total of 20 parks with an area of more than 1000 mu have been built, all of which have achieved good results. Zaixinpin
Introduce green organic coarse cereals planting exhibition garden and standardized planting exhibition garden.
Surface, through the field technical operation and demonstration effect verification, has produced a strong radiation force.
Shoot and drive.
2.7 In order to ensure the realization of standardized production, we vigorously promote the "nine modernizations" in cultivation management.
Change "integration technology"
The quality control of the whole process from the base to the dining table has been realized, and many valleys have appeared.
Typical high quality and high yield. For example, in 2005, beipiao city North Sijiazi Township South Sijiazi Village.
Concentrated planting of Chaoxingu No.5 (33hm2) resulted in an average yield of 7740kg/hm2, the highest.
The highest yield reached 9 780kg/hm2.
2.8 Build leading enterprises, cultivate green organic miscellaneous grains market and extend industrial chain.
Increase the added value of products
Project of "Green Organic Coarse Grains Production Base Construction and Food Development in Western Liaoning"
After three years of construction, a total of more than 53,300 hectares of miscellaneous grain production bases have been built, including green
The production base of organic miscellaneous grains is 210.6 million hectares, which forms scale effect and is important to agriculture.
The product processing industry provides a reliable guarantee for high-quality raw materials. At present, there are all kinds of * * * in the city.
There are 743 miscellaneous grain processing enterprises with annual production, processing and sales capacity of 1 10,000 tons, of which
60,000 tons of medium-green organic miscellaneous grains, achieving a sales income of 450 million yuan. Meanwhile, miscellaneous grains
The scale of the base has also driven the construction of the local miscellaneous grains market. The biggest miscellaneous in Northeast China
The grain distribution center is Jianping Zhuluk, and there is a 25,000-square-meter miscellaneous grain trading wholesale market.
The purchase, processing and sales of green organic miscellaneous grains have begun to take shape.
Products are mainly sold to large and medium-sized cities in China, and exported to Japan, South Korea, Germany and New Zealand.
Waiting for the country.
3 Project effectiveness
3. 1 Large-scale and distinctive.
The construction of green organic coarse cereals production base and food development, certification and labeling are all tiring.
The total scale is 2 1.600 hectares, accounting for 60% of the total certified area in the province, which is advanced.
Characteristics of agricultural regional economy and export-oriented economy. Accepted by domestic peer experts.
It is agreed that the industrialization scale and technical level of this project are in similar areas in China.
Have a leading position.
3.2 opened up a new way of dry farming.
According to the characteristics of natural geographical conditions in arid areas of western Liaoning, scientific development
Development and utilization of limited arable land, the implementation of green and organic coarse cereals standard certification, improve
The quality of agricultural products has created a new way to increase production and income in agricultural arid areas.
3.3 Create a new "scientific research+company+farmers+production base"
model
Form a virtuous circle of production, processing and sales, and promote the green and organic coarse cereals processing industry.
Develop and implement the agricultural famous brand strategy, and improve the green organic miscellaneous grains food market.
Check-in. In the past three years, the accumulated export earned 654.38+0.37 billion yuan, which promoted the export-oriented economy.
Rapid development.
3.4 Increased the added value of agricultural products.
In recent three years, the average output value of grade A green coarse cereals was 6.5438+0.92 million yuan /hm2, with an average.
The benefit is 65438+6000 yuan/hm2; The output value of organic food is 27,900 yuan /hm2, and the benefits are as follows.
24 1 ten thousand yuan /hm2. The average benefit of green organic coarse cereals is 20,300 yuan /hm2, which is higher than other crops.
The average benefit of miscellaneous grains outside the project area increased by 6.5438+0.3 million yuan /hm2.
3.5 improved the agricultural ecological environment
Green organic agriculture is ecological agriculture. Through the implementation of this project, in
Certification within the regional scope has fundamentally changed the way of agricultural planting and protection.
The biodiversity of the ecosystem and the surrounding environment is reduced and effectively managed.
In order to avoid environmental pollution, it not only provides safe food, but also promotes people and nature.
Harmony.
Through the implementation of the three-year green organic miscellaneous grain production base construction project, this is extremely
The earth has promoted the rapid development of science and technology industrialization and export-oriented economy.
Exhibition has promoted the prosperity of the secondary and tertiary industries and accelerated the development of new varieties of miscellaneous grains.
New generation. Due to the popularization of the new variety Chaoxingu No.5, the ratio of grain to grass is
1:1.3, which not only promotes the transfer of agricultural dual structure to ternary structure, but also
It also promoted the development of animal husbandry in western Liaoning. Practice has proved that building green in arid areas
The production base of organic miscellaneous grains has played an important role in the industrialization of science and technology.
The prospect is broad.
! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !
(Continued from page 24 1)
5.3 Fermentation strains
Strain is the soul of fermentation industry. In the process of producing alcohol from corn stalk,
Using modern breeding technology to cultivate efficient direct fermentation strains, in appropriate
It will make a breakthrough in adapting to special substrate conditions and simplifying production technology. If possible
Screening mutant strains resistant to high concentration of sugar can overcome cellulose raw materials.
The inhibition of hydrolysis process improves the fermentation efficiency.
5.4 Fermentation process
Some technical measures can be adopted to reduce the ethanol produced in the fermentation process.
Stop pumping, make the ethanol concentration in the fermentor ≤ 10%, and reduce the influence of ethanol on strain growth.
And the production cost is reduced.
Countries all over the world are studying the technology of producing alcohol from cellulose such as corn stalk.
Hot spots, compared with other bioenergy and alternative energy technologies, whether in economic cooperation
Rationality and technical feasibility, or resource sustainability and environmental coordination.
The advantages in all aspects are obvious, and it can also solve the problem of shortage of oil resources in China.
Shortage and environmental pollution are conducive to ensuring national energy security and social coordination.
Development.
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