| In this study, sweet sorghum straw which had not been treatmented was used as material. The effects of different sweet sorghum varieties, different fermentation strains, and different fermentation conditions including pH, inoculation amount temperature, time on the alcohol yield were studied, and then enlarge fermentation test was carried out. The effects of acid, alkali and ultrasonic-assisted enzymatic pretreatment on the impact of reducing sugar concentration in the sweet sorghum straw, the appropriate pretreatment methods were determined, and simultaneous saccharification and fermentation under the appropriate pretreatment conditions were carried out. The juice of sweet sorghum was also taken as the material. The relationship between the different Dan Baoli liquid yeast inoculum size, fermentation time, the different sweet sorghum juice soluble solids content and alcohol yield in the fermentation pressing were studied, too. The orthogonal regression model was establishmented. Test results are as follows:1. When the sweet sorghum straw which had not been treatmented was adopted to carry on a solid-state fermentation, the Silimei was suitable for fermentation variety, Dan Baoli was suitable for fermentation yeast strains.The fermentation conditions were obtained as following: pH value was initial physical pH, inoculation amount was 5%, fermentation temperature was 33℃, fermentation time was 3 d. And alchol degree of final production was 4.1% (v/v). According to the study, the Silimei straw in which soluble solids content was 16Birx and the percent of water was 76% was crushed to carry on a solid-state fermentation, if harvest yield of sweet sorghum straw was 5000 kg /mu, the theoretics of ethanol would be 400 kg, however, the output of ethanol would be 328.0 kg in fact, the alcohol yield was 82%.The Silimei straw which had not been treatmented was adopted in the 50 kg enlarge solid-state fermentation test. After 48 h of the fermentation time, the alcohol yield reached 3.5% (v/v), the concentration of total sugar was 3.58%, the concentration of reducing sugar was 0.11 mg/mL, pH value was 4.67, yeast counts were 1.52×109.The results would greatly enhance industrial production equipment utilization and reduce the cost of fermentation. 2. When four different kinds of pretreatment methods were adopted to treatment the Silimei straw:the appropriate crush degree was square hole 4.75 mm aperture sieve to crush the extent; 3% sulfuric acid concentration for the appropriate pretreatment; NaOH pretreatment methods was not suitable for handling sweet sorghum; ultrasonic processing aids digestion after 90 min pre-treatment method was the optimal.When dealing with 90 min ultrasonic-assisted enzymatic hydrolysis pretreatment of the Silimei straw, the appropriate hydrolysis conditions were as follows: the amount of cellulase was 10 mL, hydrolysis temperature was 55℃, pH value was 5.0. Under the above conditions, the concentration of reducing sugar was highest.After 90 min of ultrasonic pretreatment of the Silimei straw simultaneous saccharification and fermentation, the suitable fermentation conditions were obtained as follows: yeast inoculum was 5%, pH value was 5.0, fermentation time was 3 d, the fermentation temperature was 30℃, the dosage of cellulase was 15 mL. Under the optimal conditions, the highest alcohol content was reached. If harvest yield of sweet sorghum straw was 5000 kg /mu, the output of ethanol would be 384.5 kg, the alcohol yield was 96.1%. Compared with not treatment, the alcohol yield was raised by 17.2%.3. Through the ternary first regression orthogonal experimental design, the orthogonal regression model was set up between sweet sorghum juice alcohol fermentation products (Y) and Dan Baoli yeast inoculum (x1), fermentation time (x2) and sweet sorghum juice of the sugar content (x3): Y = 9.854 +1.619 x2 +1.209 x2x3 (1%≤x1≤5%; 1 d≤x2≤3 d; 12%≤x3≤36%).
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