Breeding Of High-sugar-tolerant Yeast

High gravity fermentation is the new trend of industrial production of alcohol, This fermentation process generates a higher alcohol concentration, and a higher sugar content in fermentation liquor. This fermented mash of high osmotic pressure. There will be a significant change in the Intracellular water activity and the composition of the cytoplasm. The cell membrane and body enzyme of yeast will be damaged. Growth and fermentation of yeast will also be inhibitd. There are many breeding resistance to high concentrations of yeast alcohol screening in China and foreign, however, breeding of high-sugar-tolerant yeast was rare. It is very beneficial for the ethanol industry's production services, if we breed high-sugar-tolerant yeast. So this paper was made a study on it. First high-sugar-tolerant yeast was domesticatd. Prepare protoplast with the well yeast; The protoplast UV mutagenesis method combining with domestication was used to screen High-sugar-tolerant Yeast. The high-sugar-tolerant yeast were then applied to ferment alcohol.The results are as follows:1. The initial yeast was domesticatd of high sugar tolerance using the method of gradually increase the concentration of sugar in culture medium. The result was as follows: The domesticatd yeast can fermentatd well in the culture medium of 30% sugar concentration.2. The domestication yeast was culture to log phase. Deal them withβ-mercaptoethanol-EDTA-PB and enzymolysis with helicase. Count the yeast colony to compute formation rate and regeneration frequency of protoplasts. The result is that the formation rate is 97.9%, and the regeneration frequency is 19.8%.3. The protoplast of domestication yeast was mutagenesised by UV. The UV mutagenesis time and distance was optimized. The results showed that the optimum mutant conditions were the irradiating time of 18 s and the irradiating distance of 20 cm. The yeast YB-23 was screen out by initial and final choose. The YB-23 can grow well under high sugar (40%) concentration condition. And it had the ability to ferment glucose under the high sugar (65%) concentration condition. And YB-23 is superior to the original strain in the aspect of fermenting power, ethanol production ability, residual reducing sugar concentration. The yeast colony, cell and stability were very good.4.The yeast YB-23 was used to do alcoholic fermentation test. This test content single-factor and orthogonal experiment, which was carry out in 10L fermenter. The results were as follows: The optimum technology of high gravity fermentation were ratio of material to water 1:1.5, initial pH 4.5, glucoamylase activity 150u/g C.edulis, Yeast inoculums 14%. The result carry out in10L fermenter was very well.? The ethanol conversion rates reach to 16.0% (v/v) after fermention for 72h.But the initial yeast only can reach to 15.1% (v/v) after fermention for 72h. Breeding yeast of alcohol production increased 5.96% than the original yeast.