Screening Of High Effective Cellulose-deposing Microbes And Ethanol Fermentation Using Rice Straw

With the development of energy crisis and environment pollution,energy structure in the world is changing from fossil energy into renewable energy.The system of the biologic energy is the leader of technology platform of the third energy revolution of the world.In the circumstance,ethanol is severed as the best alternative and fuel that saving the petrol, as the best liquid fuel,especially when cellulose ethanol is considered to be the best liquid fuel which has ecological benefit and hence it has been a focus of industrial biology's research.In order to obtain efficient cellulose-decomposing strains in the study,firstly we selected 68 strains which grew fast and had canker spot by solid medium containing filter paper as only carbon from rotten rice straw,leaves and sack of contaminative edible fungi and so on,then selected them in medium containing cellulose-Congo red,and next obtained 32 strains which had bigger cellulose-hydrolysis circle.On the basic of it,the ability of deposing cellulose in broth medium containing filter paper as only carbon and the ratio of rice straw loss and the activity of cellulase in broth medium containing rice straw as the only carbon through liquid fermentation were observed and four aerobic strains F-1,F-7, J-1,J-7 which shown the high effect of deposing cellulose,F-1 and F-7 were bacteria, while J-1,J-7 were fungi.Bacteria F-7 and fungi J-7 were the initial strains,and we conducted single factor optimization experiment about the liquid fermentation of deposing cellulose,and the results shown that the optimization condition of F-7:when it was inoculation volume of 15%and cultivated at 36℃with the initial pH of 5.0,the agitation of 150 r/min in fermentation culture medium containing 1%of Yeast powder and(NH₄)₂SO₄ as nitrogen, and the activity of CMC reached the highest point of 30.28 U which was increased by 10.7%,compared to initial cultivation condition.The optimization condition of Fungi J-7 was in liquid fermentation:when it was inoculation volume of 10%and cultivated at 36℃with the initial pH of 5.0,the agitation of 150 r/min in fermentation culture medium containing 1%of Yeast powder and(NH₄)₂SO₄ as nitrogen,and the activity of CMC reached the highest point of 70.3 U,which was increased by 25.3%,compared to initial cultivation condition.J-7 was sensitive to degraded temperature and it was cultivated at 45℃for 36 h,then was produced cellulase at 28℃,the activity of cellulase reached the highest point of 74.7 U which was increased by 5.8%,compared to the constant temperature of 28℃.The conditions of ethanol fermentation with rice straw was studied,we figured out the deposing time was 72 h by J-7 strain,15%of Yeast was inoculated and fermented for 24 h under anaerobic fermentation,and the highest concentration of ethanol was 12.92 mg/ml. The ability of deposing rice cellulose was improved by fed-batch.In procedure of ethanol fermentation,50%of culture solution was inoculated firstly,and 25%of culture solution was inoculated after 24 h and 36 h,respectively,it shown that it was useful to the production of ethanol,and the concentration of ethanol reached 13.56 mg/ml and was increased by 6.8%,compared to inoculation of all culture solution at one time. Under the optimization condition,J-7 and F-7 could depose cellulose in the short time, especially when cellulose- hydrolysis solution from rice straw by J-7 was inoculated,it shown the better effect of ethanol production,and had significant influence on the research of exploiting cellulose source and yielding of ethanol.