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Screening and Optimizting of Bacteria Coverting Lignocellose to Ethanol

Author: ZengYingYu
Tutor: ChenJieNan；HeGang
School: Central South University of Forestry Science and Technology
Course: Biochemistry and Molecular Biology
Keywords: Lignocellulose Xylose Ethanol Ferment
CLC: TQ223.122
Type: Master's thesis
Year: 2010
Downloads: 62
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Abstract


The rapid development of the global economy led to a growing shortage of oil as the representative of the types of non-renewable mineral resources, looking for renewable energy has become an inevitable trend. Fuel ethanol is recognized as the most promising renewable clean energy sources. Lignocellulosic biomass to produce fuel ethanol can not only reduce the cost of fuel ethanol production, waste treatment, environmental protection at the same time play a role. Xylose is a monosaccharide glucose content after the lignocellulosic hydrolyzate. Effective utilization of xylose is a key part of the production of ethanol from lignocellulose biotransformation. Strains of the high sugar utilization and high resistance to inhibitors of xylose fermentation capacity, therefore, has been a hot topic in the field. This thesis is based on the theory of Microbiology screened an efficient xylose fermentation ethanol production strains, according to the characteristics of xylose fermentation bacteria, isolated from the natural environment of the strain, according to the physiological and biochemical characteristics of the strains and molecular biology methods identified. Parameter optimization process of its fermentation the xylose production of ethanol at the same time laid a foundation for the strains in cellulose production of fuel ethanol. Its main contents are as follows: 1. Isolation, screening and identification of the fermentation of xylose to ethanol production bacteria using xylose as sole carbon source xylose screening plate separation, screened 22 wood from rotting cellulose-rich soil sugar fermentation strains. Xylose fermentation experiments with ethanol yield on xylose as the sole carbon source in the fermentation medium as the index, according to the detection result, the final screening an efficient xylose fermentation strain, strain was named 18. Morphological, physiological and biochemical identification of the strains of bacteria, and combined with its 16s rDNA sequence identification results show that, up to 100% of the strains of Bacillus cereus (Bacillus cereus) 16s rDNA sequence homology, ascertain that it is Bacillus cereus. 2 Physicochemical properties of fermenting xylose to ethanol production bacteria studies showed that strain 18 to adapt the pH value of a relatively wide range of tolerance studies of strain 18, can grow in a medium with a pH of 4.5 to 5.0, wherein the pH relatively good grown within the range of value of 6.0-8.5; its adaptation to the concentration of NaCl is also a relatively wide range, a NaCl concentration of 5 to 40 g / L within a medium can grow in a NaCl concentration of 15g / L Growth best. Oxidase, catalase and nitrate reduction tests were as positive. 3 Optimization of the fermentation conditions that the strain can utilize xylose and glucose to ethanol fermentation under anaerobic conditions, the maximum ethanol yield of the fermentation of xylose to 6.36954g ethanol / 90g of xylose, which is 20.11% of the theoretical yield; fermentation The maximum ethanol yield of glucose to 7.14627 g ethanol / 90g glucose, which is 21.19% of the theoretical yield. This feature has theoretical significance for the fermentation of glucose and xylose in lignocellulosic hydrolyzate, at the same time has a certain value for lignocellulose to produce fuel ethanol. Optimization of the in xylose fermentation medium based on the fermentation parameters. Strain 18 in xylose as sole carbon source, temperature 32 ° C the xylose 30g / L under anaerobic conditions cultured 72h, the highest ethanol yield reached 32.24% of the theoretical yield of the fermentation of xylose to ethanol, the associated with a certain amount of the acid generated, the pH value of 3.32.

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CLC: > Industrial Technology > Chemical Industry > Basic Organic Chemistry Industry > The production of aliphatic compounds ( acyclic compounds) > Aliphatic alcohols (alcohols, hydroxy compounds) and its derivatives > Aliphatic alcohol > Fatty Alcohols > Ethanol ( alcohol )
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