Screening, Identification And Study On Growth And Fermentation Of The Yeast With High-Yield Of Alcohol

Many countries started to develop the new energy for the reason that the oil resource became deficient day by day and the environmental pollution became serious. The fuel ethyl alcohol is at present up to the most ideal petroleum substitution energy, and it is mainly produced by fermentation. The strain's quality affects a lot on the fermentation. It is so important for reducing the production cost and developing large-scale industrialization production of alcohol that the strains with fine character can be screened and improved.69 isolates out of different environments were screened for alcohol-producing yeast with high yield. After the stair-screening by TTC means,the second-screening for high alcohol tolerance and the third-screening for high yield of alcohol, 4 strains of yeast with high yield of alcohol and tolerance were obtained which were named Y-1, Y-2, Y-3 and Y-4. With the methods that were mentioned in The Yeast: a Taxonomic Study(3rdedition), such as saccharide-fermentation experiment, carbon source assimilation experiment, nitrogen source assimilation, non-vitamin growth experiment, 50% glucose-yeast extract growth experiment, 37℃growth experiment and cycloheximide-resistance experiment, Y-1 was classified into Saccharomyces; Y-2 was identified as Candida sake and Y-3,Y-4 as Saccharomyces cerevisiae.And then, the study focused on the growth characteristic of the 4 stains. The optimum growth temperature of Y-1, Y-2, Y-3 and Y-4 separately was 30℃,32℃,30℃,30℃; the optimum growth pH value of the 4 stains separately was 5.5,5.0,4.5,4.5; the initial inoculum was an important factor in affecting the growth of Y-1, Y-2, Y-3 and Y-4; temperature affected a little on the growth of Y-1 but a lot on the growth of Y-2, Y-3 and Y-4; pH value affected a little on the growth of Y-1, Y-3 and Y-4 but a lot on Y-2's.With the potassium dichromate colorimetry, the optimum fermentation temperature of Y-1, Y-2, Y-3 and Y-4 separately was 32℃,32℃,30℃,30℃; the optimum fermentation pH value of Y-1, Y-2, Y-3 and Y-4 separately was 5.5,5.0,4.5,4.0; the temperature affected a lot on the fermentation curve of Y-1, Y-2 and Y-4, but a little on the Y-3's; pH value affected a lot on the fermentation curve of Y-1, Y-2 and Y-3, but a little on the Y-4's; the initial inoculum was not the important factor for the fermentation of the 4 strains.The 4 strains were inoculated into the medium with different content of alcohol in it, then the alcohol tolerance came out with the death rate of the 4 strains. The alcohol tolerance of the 4 strains was about 20% (v/v).On the optimum condition for fermentation, Y-1, Y-2, Y-3 and Y-4 were fermented for 72 h in the bottle, after then, the alcohol content (v/v) in the liquid of Y-1, Y-2, Y-3 and Y-4 reached 10.44%, 11.46%, 10.92% and 10.84%.