Study On Fuel Ethanol Continuous Fermentation By Thermotolerant Saccharomyces Cerevisiae S-13

With the problems of increasing shortage of mineral energy resources and environmental pollution, more and more countries became developing new renewable energies, especially fuel ethanol which has typical advantages, but high-cost in production process is the main limit factor for large-scale application. From the point of fuel ethanol production distribution cost structure using the starch grain as raw materials, the consumption of raw materials and energy is as high as 90%. Therefore, how to reduce raw material and energy consumption became the critical technologies of fuel ethanol development and need to pay attention on the development of new technology of fuel ethanol production at the same time.In this paper, my expriments using the thermotolerant Saccharomyces cerevisiae S-13 which was screened in our laboratory as an original strain.Based on the results optimization of glucose fermentation medium by single factor and the four factors, four levels orthogonal experiments, designed follow formula:glucose 18%, peptone 0.3%, yeast extract 0.4%, KH2PO40.04%, (NH4)2SO40.1%, MgSO4.7H2O 0.02%, CaCl20.2%; fermentation conditions:temperature was 37℃, pH value was 3.5-4.5, inoculation was 4% and incubate 48 hours. Ethanol concentration was 10.5 (v/v) under these conditions. Based on the results optimization of sweet sorghum stalk juice fermentation medium by single factor and the four factors, four levels orthogonal experiment, designed follow formula:sweet sorghum stalk juice 18%, KH2PO40.04%, (NH4) 2SO40.6%, MgSO4·7H2O 0.02%, CaCl2 0.1%; fermentation conditions was as same as ethanol fermentation which using glucose as raw material. Ethanol concentration was 9.5%(v/v) below above conditions.Under the optimum technical conditions, tests for the physiological and biochemical characteristics of the strain were carried support for the opitimizing ethanol production techniques. The results showed that the genetic stability of strain was stable, the ethanol tolerance was 14%(v/v), the sugar tolerance was 60%, the lethal temperature was 66℃-67℃, the NaCl osmotolerance was 15% and the strain can grow from pH value 3.0 to 7.0 with more acid-alkali tolerance.Study on 5 kinds of continuous fermentation processes:Single-stage continuous fermentation, Double plus continuous fermentation, Yeast recycling continuous fermentation, Fermentation Wastewater continuous fermentation, Immobilization continuous fermentation. Selection a more appropriate continuous fermentation produce ethanol using sweet sorghum stalk juice by comparing the ethanol yield and stability production.The results were as follow:Single-stage continuous fermentation was taken 80 hours, and the highest ethanol concentration was 8.6%(v/v); Double plus continuous fermentation was taken 12 days, and the highest ethanol concentration was 10.5%(v/v); 30% Fermentation Wastewater continuous fermentation was taken 12 days, and the highest ethanol concentration was 7.8%(v/v); Yeast recycling continuous fermentation was taken 12 days and the highest ethanol concentration was 10.1%(v/v); Strengthened Immobilization continuous fermentation was taken 20 days, the highest ethanol concentration was 10.1%(v/v), and the lowest ethanol concentration was 8.5%(v/v).Aligning the ethanol yield and stability production 5 continuous fermentation processes, finally we chose sweet sorghum stalk juice as raw materials and using Strengthened Immobilization continuous fermentation to produce ethanol. The results are as follow:the experiment Continued 20 days. The highest ethanol concentration was 9.4%(v/v), the lowest ethanol concentration was 8.3%(v/v), and reduction rate was 11%.