Study On Very-high-gravity Alcohol Fermentation From Cassava

In recent years, more and more people want to produce alcohol by very-high-gravity fermentation (VHGF), because of the superiority of the steps of distillation and waste liquid. This method has been applied in industrial production, and it becomes a more and more important study field of produce alcohol and can improve the concentration of alcohol. But as the improvement of fermented liquor concentration, the high sugar can suppress the Saccharomyces crevasse because of osmotic pressure, the high concentration of alcohol in the later time can also toxic the Saccharomyces crevasse, these disadvantages can influence the process of fermentation, and cause the lower concentration of alcohol. On one hand we can resolve this problem via selecting Saccharomyces crevasse that can resistant high osmotic pressure and ethanol tolerance well, on the other hand it can decrease the disadvantage influences. Produce alcohol technical from starch can be of two kinds: saccharification–fermentation and simultaneous saccharification and fermentation (SSF). To find a proper method and increase the fermentation efficiency, the primarily researching jobs about this paper can be stated as follows:1.Research on saccharification-fermentation, determine the best liquefy condition that the best temperature is 105℃, and the best time is 2h; the best saccharifiction temperature is 60℃. Prepared different culture medium, then carry out saccharification–fermentation, the results found that it is feasible to saccharification–fermentation when the concentration of fermentediquor is low, the fermentation efficiency can meet requirement. But as increase the concentration, the concentration decrease, and the fermentation efficiency is lower, too. So, saccharification-fermentation is not fit to the very-high-gravity fermentation.2.Research on brewing diagram of saccharifying enzyme under different temperature and different sugar concentration, investigate the possibility of simultaneous saccharification and fermentation (SSF). The results revealed saccharifying enzyme has part activity under 33℃, but it is worse than 60℃, that means the proper temperature of saccharifying enzyme has part consistency to fermentation temperature. Under this temperature, the saccharifying enzyme can hydrolyze material gradually to produce glucose, which is the crucial of the feasible. Compare saccharification–fermentation with SSF, the results revealed that under VHGF, the SSF is better than saccharification–fermentation obviously. SSF is a proper technical for VHGF.3.The scale-up experiments of SSF from cassava were investigated, the results shows SSF can get a better effect while the concentration of total sugar is near 24%, but if the concentration is higher than 24%, the fermentation efficiency will decrease, and the higher the worse. After analysis, we think that in VHGF, many factors can cause Saccharomyces crevasse grow and breed redundantly, such as high total sugar, high initial reducing sugar and too much oxygen which has access to the fermented. This can go against transforming alcohol, and lead to the lower alcohol concentration in the end and fermentation deficiency is lower.