Screening Of The Strain Fermenting Sweet Potato To Ethnaol And Optimization Of Simultaneous Saccharification And Fermentation Conditions

Developing fuel ethanol industry is very important for exploring substitute energy source for petroleum all of the world nowadays.Considering the food safety and our country's actual situation,during eleventh five-year plan,the development of fuel ethanol industrial should choose non-grain raw materials.In the present study,a strain of yeast that produce fuel ethanol was screened,and its fermentation process was studied.The main results were as follows:1.Two strains are selected form 113 samples by TTC and fermentation method. Then,a strain naming Sky-1.5 can normal growth and development on 42℃was selected from these two strain with uv mutagenesis and high temperature.The ethanol fermentation experiment using sweet potato as raw material showed that Sky-1.5 can produce 9.7583%(m/m) ethanol and survival reducing sugar is 2.08g/L,glucose utilization ratio is 87.53%.According to the morphological characteristics and assimilation physiological tests,the strain was identified as a strain of saccharomyces cerevisiae.2.The fermentation kinetics of the strain Sky-1.5 of simultaneous saccharification and fermentation using sweet potato as raw material was studied.The mathematical kinetic models describing the biomass growth and product formation were established on the base of the formula of the biomass specific growth rate and the biomass growth rate.The comparison of test data and the model suggested a reasonable regression,which indicated that the model could reflect the fermentation process and the kinetics mechanism very well.3.The culture medium and conditions of Sky-1.5 for fuel ethanol production were investigated and optimized with one-factor-at-a-time experimental design and response surface methodology.The fermentation conditions for fuel ethanol was optimized using JMP software with the Plackett-Burman design and Design-Expert sofeware with response surface method.Firstly,Plackett-Burman design was used to evaluate the influence of related faetors.The results showed that initial pH, inoculation amount,fermentation temperature were the main affecting factors.Then, the Box-Behnken design and response surface analysis were used to determine the optimal leves of the main factors.The results indieated that the optimal fermentation conditions for fuel ethanol production was as follow:initial pH 4.4,inoculation amount 8.3,fermentation temperature 36.7℃.Under the optimal conditions,the utilization rate of starch has increased to 89.38%form 86.77%.4.According to the optimal conditions,the batch fermentation was carried out in 50 L fermentor to demonsteate the result of optimization.The sweet potato starch was mostly transformed to fuel ethanol after simultaneous saccharification and fermentation for 72 hours,the utilization rate of starch has reached 89.43%.