The Research On Ethanol Production By Constructing Mixed Microbial Flora Of Straw Degradation

Earth formes about 100 billion tons per year plant organic matter, is the most widely distributed in nature, the most abundant, inexpensive but renewable resourses, if these resources is used effectively to solve human environmental pollution, food shortages and energy crisis is important significance. Straw cellulose is the main southern China straw, the traditional approach is not only pollutes the environment and the low utilization rate. This study was isolated from samples of rice straw degradation ability of stronger strains of bacteria by way of building mixed microbial degradation of straw, to shake flask experiments, and the saccharification process of fermentation conditions were optimized, a preliminary study on mixed bacteria Saccharification liquid fermentation of ethanol production. Research summarized as follows:(1) This experiment screened by congored plating test and straw fermentation compound sieving from the paddy soil, cow rumen, cow dung, we get three strains which produce cellulases was identified as an Aspergillus and two bacteria. Use these three strains and Streptomyces, Trichoderma reesei, Trichoderma koningii and Hypocrea jecorina which are preserved by our laboratory to do straw fermentation enzyme test. Trichoderma reesei produced the highest activities of CMC activity and FPA activities were 3.193IU/mL and 1.617IU/mL. And its optimum fermentation conditions which produce the highest sugar are as following:straw powder 6%, wheat bran 5%, initial pH4.5, fermentation temperature 30℃, fermentation time 7 days, sugar producing was optimized to 14.971mg/mL, which is about 1.4 times higher than before.(2) By plating screening, straw fermentation rescreening, two strains were isolated from samples of hemicellulase production strain was identified as Aspergillus and Penicillium. Using these two strains to do the second screening test of enzyme production, we get the result of BW2 Penicillium produced higher activity, that hemicellulose activity reached 462.1U/mL. And its optimum fermentation conditions which produce the highest sugar are as following:straw powder 7%, wheat bran5%, initial pH6.5, fermentation temperature 28℃, fermentation time 6 days, sugar producing was optimized to 14.754mg/mL, about 1.6 times that before optimization.(3) We isolated a strain from samples and Pleurotus ostreatus which preserved by our laboratory which can emerge a clear and transparent circle in phenyloxazole. The two strains were second screening test for the enzyme production, in which activity was higher in the Pleurotus ostreatus production, guaiacol oxidase activity and manganese dependent peroxidase activity were up to 81U and 0.556U, its one of single bacteria factor optimization test, get the best conditions for mushroom sugar: straw powder 8%,6% wheat bran, initial pH5.5, fermentation temperature 28℃, fermentation time 10 days, the optimal sugar yield for the 14.754mg/mL about 1.7 times before optimization.(4) Degradation of rice straw mixed fermentation:Pleurotus ostreatus, Trichoderma reesei and Penicillium species compatibility tests showed that the growth of Trichoderma reesei than Pleurotus ostreatus obvious advantages, competitive inhibition of the former on the latter role, the first mushroom for fermentation of straw to prevent mildew can be effectively inhibited. Three strains of rice straw degradation of the mixed fermentation The optimum conditions are as follows:6% added rice straw, bran 3%,the first access mushroom set temperature of 28℃7 days,and then access Trichoderma reesei and Penicillium home 32℃3 days fermentation, initial pH of 6 mixed fermentation when the sugar reaches the highest 19.52mg/mL, is 1.28 times higher than before optimization.(5) Using 4 kinds of yeasts:Saccharomyces uvarum, Schizosaccharomyces, Saccharomyces cerevisiae and Angel Yeast to produce ethanol in yeast fermentation saccharification liquid using the straw as the main carbon source, the strongest capacity of ethanol production, was 3.172% (V/V), the residual sugar content is low, for 2.097mg/mL. Therefore chosen Angel Yeast to do the follow-up study. After the straw saccharification fermentation media were added after the urea, peptone, beef extract, ammonium sulfate, and ammonium nitrogen in order to determine the five common solutions in the straw saccharification also added to different nitrogen sources on ethanol production of Angel Yeast. The results show that urea as nitrogen source, the highest level of Angel Yeast alcohol, residual sugar low. Therefore chosen as the straw saccharification liquid urea ethanol fermentation medium follow-up of additional nitrogen source.(6) By plate screening, straw fermentation screening,from sample decomposition of xylose was isolated strains with better marked,identified as yeast. Second screening test using fermentation of alcohol production, the ethanol yield of 1.454% (V/V). After the straw saccharification fermentation medium by add nitrogen urea, xylose fermentation strains producing ethanol fermentation test, the ethanol yield 3.265 percent, residual sugar 3.582 mg/mL, ethanol yield of 0.205g/g (alcohol/ consumption of sugar). Add Angel Yeast while strains of yeast and fermentation of xylose fermentation ethanol production test, the ethanol yield 4.156 percent, residual sugar 1.130 mg/mL, ethanol yield of 0.226g/g (alcohol/consumption of sugar).