Studies On The Breeding Of High Concentration Ethanol Producing Yeast Strains

The thesis probes into the character of high osmotic pressure plate, azure plate, alcohol tube and TTC plate with the method of incur lotion on the plate. The merits and demerits to the above screening plate are found. And the initial screening method made up of the high osmotic pressure plate and TTC plate is determined, and proved by using it to screen the mutant strains obtained from protoplast autogenesis by ultraviolet. Beginning with the characters of alcohol yeasts strain, the paper studied the factors on the protop]ast generation rate and regeneration rate, such as pretreatment, initial culture, lysozyme concentration and lytic time. The optimum conditions about protoplast generation and regeneration were got: no pretreatment, treating the cell by 5% Zymojyase lissome for 25 mm, and the pr髏oplast generation rate is 99.66%, regeneration rate is 4.7%. The lethality curve of protoplast by ultraviolet was got, and the regeneration strains exposed under ultraviolet for 10, 15, 20 seconds were selected to be screened. After the initial screening by two plates, 114 strains are selected and fermented. The figure is 9.6% of total colonies, The characters of strains are determined. The strains producing high alcohol concentration is 46% of that of selected strains, and a better strain was selected from them. The optimum technological factors were studied, such as the corn materials dealt with the different methods, the weight ratio between material and water, the amount of inoculation, the amount of the ~- amylase added, the amount of the saccharilase enzyme added, the pH numerical value, the amount of the cellulose added and the amount of the nutrition material. Some of the conditions were optimized with the 3 orthogonal measure. The optimum conditions were got: using the corn made with extra care, adding 0.1% cellulose and 1SU/g ~-amylasc, keep the corn with the 600C for 20 minutes and liquided in the 800C for an hour, adding 100U/g saccharilase enzyme, adding 0.001% casein hydrolysate, adding 5% wort and 0.5% extract of yeast after 24 hours. On the above conditions, strain Y-l-3-23 can produces 13.5%(v/v) ethanol in 30 0C after 72 hours. Through the stabilization experiments, the optimum technology conditions were decided, and the energy cost and product cost were decreased.