Screening Efficient Degradation Of Hemicellulose Strains And Study On Utilizing Straw To Ferment Ethanol

In recent years, due to the gradual depletion of fossil fules running out, bio-ethanol has been rapidly developed. Using some grains such as corn for bio-ethanol production has caused a heavy burden to the world food supply. Inedible materials such as lignocellulose is considered an ideal substrate for bio-ethanol production. The lignocellulose hydrolysates both six carbon sugars and five-carbon sugars are fully and efficiently transformed into bio-ethanol is prerequisite for industrial progress to gain maximum benefit. In order to efficiently use biomass resources, enhance the utilization ratio of cellulose and hemicellulose, increase ethanol yield, the key is to obtain strains with high cellulase and hemicellulase activity and investigate their fermentation technology.It have made great progress on cellulase production and cellulose conversion of fuel ethanol both at home and abroad, while the semi-cellulose and hemicellulose conversion is relatively few. In order to efficiently use biomass resources, the research use screening efficiency degrading bacteria from the edge of rice Tada humus soil, decaying leaves, cow dung, vegetable garden next to the rotting straw, humus and decomposed rice straw in rice fields and other samples as the starting point, after enrichment culture and purification, the total hemicellulose degrading bacteria is 42 strains, including 37 bacteria and 5 fungi. Then the ratio of rice straw loss and the activity of cellulose are observed, determine FⅢ1、FⅤ3、BⅤ5 as the further study strains, in witch FⅢ1、FⅤ3 are fungus, BⅤ5 is bacteria. After strain identification, FⅢ1 is Penicillium notatum, FⅤ3 is Penicillium expansum, B V 5 is Paenibacillus sp..Fungi FⅤ3 and FⅢ1 were the initial strains, and we conducted single factor optimization experiment including initial pH of medium, straw power/bean dregs, the fermentation temperature, initial ratio of water in medium, percentage of inocilum, medium contents, fermentation time about the solid-state fermentation, and get the optimization condition.The hemicellulosase activity of fungi FⅤ3 was 7.94 IU/ml; fungi FⅢ1 was 6.21 IU/ml. However, reducing sugar content in the fermented liquid is also relatively low, it is 0.79mg/ml. So the mixed bacteria test was teken account into the next step, selected the hemicellulose degrading bacteria FⅤ3, BⅤ5 and the cellulose degrading bacteria D-7 existed in laboratory to combine in the mixed bacteria test. Fungi FⅤ3 and bacteria BⅤ5 combination is the optimal combination of mixed fermentation, reducing sugar content is 1.48mg/ml, increased about 80% higher than single fermentation. After solid fermentation container is expanded, in 15L barrel, reducing sugar content get to 4.34mg/ml, increased 193% than the previous scale. Fungi FⅤ3 and bacteria BⅤ5 were cultured in solid fermentation medium, and then the fermentation product was saccharificated at high temperature, the conditions of which was confirmed as follows:the start time of saccharification is at 96 h, the optimum temperature of saccharification is 50℃, the optimum time of saccharification is 48 h.The saccharification products is co-fermentated with Pichia pastoris and Saccharomyces cerevisiae, the highest conversion rate from rice straw to ethanol obtained is 9.27%, the concentration of ethanol is 16.59mg/ml.