The Effects Of UVB Radiation On Physiological Properties Of Saccharomyces Cerevisiae And Application

The effects of UVB radiation cultures on the metabolism and physiological properties of yeast and active materials in yeast were studied in the dissertation. The optimum production conditions of LIVE YEAST CELL DERIVATIVE(LYCD) applied in the cosmetics with the functions of prevention-sun, moist skin and moisture were determined. In addition, a mutant (UV-7-36-12-17) of Saccharomyces cerevisiae with enduring high alcohol concentration and high temperature was successfully breeded by the techniques of UVB radiation culture and heat strikes. The research results as follows:1. In the yeast cultural processes under UVB radiation with 70r/min shaker, because the glucose concentration in the cultural broth was decreased from 4% to 0.05% after 6h, whether 297nm lamp or 312nm lamp, adding glucose procedures were important to content the normally physiological metabolism of yeast. The pH of the cultural broth dropped from 5.0 to 3.0 after 12h with 297nm lamp. The pH of the cultural broth just dropped to 3.6 after 12h with 312nm lamp. But adding NaOH solution was needed in both cultures. Nevertheless, when the medium prepared with buffer solution of citrate and sodium citrate in pH5.0 was used, the pH of cultural broth would all along keep above 4.0 in the cultural cycle of 84h.Therefore, the operation was simplified and the active materials defended UVB harm were easily formed in yeast. At one time, the ability of producing-alcohol from glucose of yeast declined in the UVB radiation.2. The morphology and cytoplasm of yeast brought also changes in the UVB radiation culture. The growth of yeast was restrained by UVB. When the initial cell numbers were 1×10⁶cells/mL and 1×10⁷cells/mL, the cell amount of broth in the UVB radiation culture was much less than that of control. The most values of cells were 0.85×10⁸cells/mL and 1.08×10⁸cells/mL, 1.07×10⁸cells/mL and 1.46 ×10⁸cells/mL, respectively. When the initial cell numbers were 1×10⁸cells/mL, the growth of yeast cell reached zero net growth after 24h. The most values of cells were 2.75×10⁸cells/mL and 2.50×10⁸cells/mL, respectively. The cell amount of broth in the UVB radiation culture was more than that of control. When the initial cell numbers were 1×10⁹cells/mL, the yeast cell numbers of the control evidently decreased in the late culture ,but the downtrend of the yeast cell numbers in UVB radiation culture did not occur. The most values of cells were 17.90× 10⁸cells/mL and 19.30×10⁸cells/mL, respectively.3. When the inoculation was 2% active dry yeast in the medium adding 0.05% yeast extract in UVB radiation culture, the contents of RNA in the yeast cells increased from 8.94% to 9.88% after 72h. If the culture was continued, the value would drop. The change trend was similar to the change of the OD₂₆₀ valueof the cultural broth. The contents of protein in the yeast cells did not almost change, but the OD28o values of the cultural broth increased 95.8%. The contents of GSH and activities of SOD, CAT and POD in the yeast cells decreased. The contents of trehalose, ergosterol and polysaccharides in the yeast cells all enhanced. The contents of trehalose reached the most value 113.9mg/g yeasts after 60h. The contents of ergosterol reached the most value 15.43mg/g yeasts after 84h. The contents of polysaccharides increased all through to 22.60% after 72h.4. The hydrolysis of yeast cells cultured by UVB radiation after 72 had the most absorbency of UV. The optimum enzymatic conditions were the contents of suspension yeast 10%, Neutrase 3% (dry weight of the cells), pH6.5, 52 °C and the time of hydrolysis 26h. The hydrolysis of yeast cells after UVB radiation culture was prepared by centrifugation. The OD297 and OD365 values were 3.19 and 2.88, which was the 1.20 and 1.82 times of the control. Its UV absorbency was more than 95% in 280⁴00nm. It was worthy biological prevention-Sun products5. The optimum processes conditions of LYCD were the medium for UVB radiation including 0.05% yeast extract, which was prepared with buffer solution of citrate and sodium citrate in pH5.0;the inoculation 2% active dry yeast;cultural temperature 28°C³0°C;shaker revolution 70r/min;cultural time 60⁷2h under 312nm lamp radiation;the suspension prepared with Ph6.0 buffer solution of yeast 10%, Neutrase 3% (dry weight of the cells), pH6.5, 52.5 °C and the time of hydrolysis 28h. And then, the hydrolysate was centrifuged and ultrafiltrated to get LYCD I and LYCD II. In the LYCD II, the contents of a -amino nitrogen and nucleotides were 505.95mg/L and 2882.66mg/L, respectively. The productive rate of little molecule glycopeptide with 0-glucopeptide bond was 3.7g/g dry yeast.6. The moisturizer effects of skin cream adding 5mL and lOmL LYCDII increased 13.6% and 17.0% than the control after applying 60min and 120min, respectively. The SPF values of the protection-sun liquid adding 5mL and lOmL LYCD I were 27.4 and 35.6. The protection-sun effects enhanced 75.6% and 128.2% .7. The optimum ethanol fermentation conditions of UV-7-36-12-17 enduring high concentration alcohol and high temperature were the rate of raw material and water 1:2.2;the temperature of liquidization 95 °C;time of liquidization 90¹20min;saccharifying enzyme 125 u /g raw materials;time of saccharification 30⁶0min under 60 °C;inoculation volume 8%¹0%;shaker rotate speed 70⁹6r/min;the most fermentative temperature34³6°C;fermentation cycle 72h;ethanol concentration in broth 14.3%(v).