Study On The Production Of Fuel Ethanol From Sorghum Straw By Mixed Bacteria Fermentation

The purpose of this study was use the wax layer of Candida lipolytica to decompose the surface of sorghum stalk,then the fiber bundle structure of straw was disintegrated by Trichoderma viride G2, finally the use of Bacillus S3 to swallow the remnants. In order to relieve the feedback inhibition of sugar, ethanol fermentation by inoculation of wine active dry yeast, make the produced sugar in time to be used, so as to speed up the speed of straw degradation. The main results were as follows:1 Study on cellulase production by mixed fermentation of Trichoderma viride and Bacillus sp.The growth and enzyme production conditions of three Trichoderma viride and six Bacillus screened were studied. With cellulase system-wide, and high activity as the principle.Using 3,5-two nitro Salicylic Acid Colorimetry (DNS method),the optimal combination of Trichoderma viride G2 and the Bacillus S3 was determined. The results were as follows:(1) The best inoculation method of mixed bacteria was first to meet Trichoderma viride G2.Then after 12h, inoculated with Bacillus S3. Inoculation ratio:Trichoderma viride G2:Bacillus S3=1:2.(2) Through the Burman Plackett-design,The key factors influencing the activity of enzyme were determined by the ratio of carbon to nitrogen, the initial pH, and inoculation amount.Using these 3 factors to make Design-Expert response surface analysis. The optimum conditions for enzyme production were determined. C/N was 9:2, the initial pH was 6.4? inoculation volume was 6.3%.Under this condition, FPA enzyme activity was 438.89U/mL, It was 2.91 times as much as the starting strain of Bacillus S3,2.75 times of Trichoderma viride G2,and 1.29 times before optimization of mixed bacteria.2 Study on the production of cellulase by mixed fermentation of Candida lipolytica, Trichoderma viride and Bacillus sp.The wax layer surface of sorghum stalk can be decomposed of Candida lipolytica. Study on the mixed growth and enzyme production of three strains of Candida lipolytica, Trichoderma virideG2 and Bacillus S3. The results were as follows:(l)The best inoculation method was first inoculated with 3% solution of the seed liquid of Candida albicans in the fermentation medium, then after 24h, inoculation of 6.21% mixed bacteria 2 culture medium in the fermentation medium. Controlling the fermentation conditions. Results show, CMC enzyme activity and FPA activity were the highest.(2) On the basis of single factor experiment, the response surface analysis of Design-Expert was carried out. The optimal conditions for the growth of three strains of bacteria were identified. Fermentation time was 1.9d> speed was148r/min> the fermentation temperature was 30?. Under this condition, FPA enzyme activity was 533.89U/mL. It was 3.54 times as much as the starting strain of Bacillus S3,3.34 times of Trichoderma viride G2,1.59 times before optimization of mixed bacteria, and 1.22 times after optimization of mixed bacteria.(3)Through the study on the enzymatic properties of the enzyme produced by the compound bacteria.The optimum pH for enzymatic reaction was 5.5. In the range of pH4.5-6.6, enzyme activity showed high stability, keep 75% to 85% of the initial enzyme activity; 50?for the most suitable enzyme reaction temperature. In the range of temperature 40 ? 60?, the activities of CMC and FPA were stable and the activity of enzyme was higher..3 Study on the production of fuel ethanol from sorghum straw by mixed bacteria(1) Control group test:production of ethanol by simultaneous fermentation of untreated sorghum stalk, the measured alcohol was 2.5% (v/v).(2) Through 3 strains of mixed fermentation of hydrolysate of sorghum straw pretreatment.By using response surface design, the best fermentation conditions for ethanol production for sorghum straw were:the fermentation temperature was 31?. yeast inoculation rate was 3.7%, fermentation time was 5d?the measured alcohol was 5.3% (v/v), alcohol ratio increased 2.12 times compared to the control group.