Studies On Stress Response Of Yeast Cell And Derivative Produced Under Hyperosmosis, Low Temperature And Oxidative Condition

This study was based on stress response of yeast cell under hyperosmosis, low temperature and oxidative condition. Live Yeast Cell Derivative (LYCD) was produced by yeast cell, which was pretreated by low dose hyperosmosis, temperature and oxidative condition. The experiment setup the new method producing LYCD by selecting hyperosmotic mutant. And protective effects of LYCD on yeast cells damaged by H₂O₂ and UV were studied.After being pretreated with a sublethal dose of either oxidative or osmotic stress, yeast cells could withstand a subsequent higher dose of the two stress. And cross adaptation also existed between the low temperature and oxidative stress. The cross adaptation indicated that damage mechanism of hperosmotic and low temperature stress were similar with the one of oxidative stress, some similar substance was produced by yeast cells under the three stresses.The following conclusions were drawn by testing the change of antioxidants and MDA in yeast cell : pretreating of low dose could increase the content of GSH , the activity of SOD and CAT, and the total anti-oxidative capability(T-AOC), could reduce the accumulation of MDA. And these induced the resistance to lethal concentration of H₂O₂. Furthermore study showed that hyperosmotic, low temperatue and oxidative stress may share a common mechanism of damage.LYCD_KCl and LYCD_LT were produced by breaking up the yeast cells ,which were pretreated with hyperosmosis and low temperatue. The results showed that LYCD_KCl and LYCD_LT could protect cell to resist oxidative condition caused by H₂O₂ and UV. The optimum conditions of producing LYCD_KCl and LYCD_LT were as follow: the concentration of KCl is 1%, and the treating time is 90min;the temperature is 4℃, and the treating time is 60min.After UV treating, the hyperosmotic mutant was selected. And it had the more ability for resistance to lethal dose of oxidative condition. The extract of mutant had almost biological activities. At the same time, the activities of GSHL SOD and CAT in mutant were higher than the initial strain, and pretreated also increase content of antioxidants and decrease the level of MDA.Through protein electrophoresis experiment, the yeast pretreated with low dose H₂O₂ and hyperosmosis were analysed. Some changes were induced by H₂O₂ and KCl, which were not made in untreated cells. Some other changes were induced by H₂O₂ or KCl, indicating that the existence of a set of unique peroxide-inducible proteins and unique hyperosmotic proteins.Protective effects of LYCD on yeast cells damaged by H2O2 and UV were studied. Oxidative damaged models of yeast cells damaged by UV (20W, 30cm, 60s) and H2O2 (lOmmol/L) were established. The survival rates of yeast cells were increased by addition of LYCD in the models. And LYCD could also enhance the activities of GSH, SOD, CAT, and decrease the level of MDA in supernates of UV damaged yeast cell model.