Celluar Memory Of Saccharomyces Cerevisiae In Cellulosic Ethanol

The inhibitory compounds during the pretreatment of igocellulosic biomass and the low efficiency in xylose utilization are the main factors that limit the efficient commercial production of cellulosic ethanol.Because of the complexity of the metabolic pathway in Saccharomyces cerevisiae,it is difficult to solve the problems by single-gene manipulation.well,celluar memroy has been observed in several organisms during the survival of adverse conditions,therefore,to explore celluar memory of Saccharomyces cerevisiae and its mechanism will be of great importance in cellulosic ethanol production.In this study,when Saccharomyces cerevisiae BY4742 were repeatedly cultivated in medium containing multiple inhibitors in Lignocellulose pretreatment,the strains wound have a rapid adaption,the lag phase was shortened to 10 h from 20 h.Well when the srains was transferred to the medium without inhibitors,the tolerance of the strain will degradate.At the same time,Saccharomyces cerevisiae has celluar memory towards xylose utilization.When the stain is cultivated in mediums of glucose,its ability of xylose utilization will degradate,well the ability of xylose utilization will recover soon after the strain was transferred to mediums of xylose again.To explore the mechanism of celluar in Saccharomyces cerevisiae.The effect of histone modification genes on cellular memory of tolerance was screened by single gene deletion.and,two genes about histone demethylation,JHD1 and RPH1,affected cell memory most obviously.Under the condtion of 90% multiple inhibitors,the value of cellular memory of the two mutants was 0.034 and-0.022,much lower than that of the contrasting strain,which had a cellular memory of 0.180.When we overexpressed JHD1 and RPH1 in the corresponding deletion mutants,the cellular memory reversed.The influence of these two genes on cellular memory was confirmed.By mutating H3K9 and H3K36 in histone,the modification site of JHD1 and RPH1,we found that the H3K36 Q mutant had a cellular memory of 0.150 under the condtion of 90% multiple inhibitors,much lower than the contrasting strain,which had a cellular memory of 0.521.we finally confirmed that the methylation of H3K36 was a significant modification that regulate cellular memory in this process.At the same time,modification of histone acetylation was considered to have great influence on celluar of xylose utilization in Saccharomyces cerevisiae.On the other hand,a short-term adapion was used in this study to improve the ethanol yield in separate hydrolysis and fermentation of lignocellulose.When the recombinant Saccharomyces cerevisiae was precultured in the wash water of lignocellulose,the ethanol yield was improved by 23% after 72 hours of fermentation.