Isolation, Screening And Application Of Fuel Alcohol-producing Yeasts With High Yield

115 isolates out of different environments were screened for fuel ethanol-producing yeast with high yield. Among them, the strain SP-48, which was able to use maize as fermentation substate to produce maximally alcohol, was identified as Saccharomyces cerevisiae based on its biophysiological and biochemical characteristics, and employed for further studies.S. cerevisiae strain SP-48 grew the best in 36℃ and a pH of 4.5, whereas its optimum fermentation temperture and pH was 30℃ and 4.5, respectively. It was seen that temperature and initial inoculum's concentration were 2 important factors in affecting the growth and fermentation of strain SP-48. S. cerevisiae SP-48 showed good tolerances to various stresses including acids, alkalis, and osmotic pressure. Also, strain SP-48 showed better resistances to high concentration alcohol and byproducts than the produced-commercially ADY (active dried yeast).If 33.3%(w/v) concentration of crude corn in fermenting material, 300 units alucoamylse per gram of raw corn, 6%(v/v) inoculum size of the yeast, and initial pH of 4.5 were fixed, orthogonal test indicated that strain SP-48 produced the highest amount of alcohol after incubated at 30℃ for 72 hours. Moreover, if strain SP-48 was inoculated to 10 L fermentter and controlled under the optimal conditions metioned above for alcohol production, the yield of alcohol at the end of fermentation was 16.2%(v/v). In the case of 25%(v/v) of the raw ground corn concentration, this strain produced only an alcohol level of 12.0%(v/v). In the case of 20%(v/v) of the raw ground corn concentration, the alcohol amount produced by strain SP-48 was only 9.3%(v/v).