Study On High Sugar Tolerance Of Baker's Yeast Against Freezing Strain

Baker's yeast will face many kinds of stress in the actual dough fermentation,especially in the sugar-containing dough.There are two industrial breads yeast strains preserved in the laboratory,one is industrial breads yeast BY14(no.1)and the other is BYCPM(no.2)with high expression of MAL62 on the basis of BY14.Preliminary experiments show that the no.2strains of frozen resistance ability is increased strain 1,due to the resistance to freezing yeast ability and the ability to resist stress have positive correlation,therefore,this topic proposed with common commercial yeast and sugar yeast as a reference,test no.1 and no.2 strains of high sugar tolerance ability,and transcriptome analysis was performed on the two strains,try a preliminary explanation to increase industrial yeast strains after the maltose metabolism patience ascension.The main findings are as follows:(1)Under different sugar concentration culture conditions,trehalose content in yeast cells accumulated rapidly with the increase of sugar concentration;The intracellular glycerol content of yeast increased rapidly.From the point of view of the fermentation terminal content and growth rate of these two intracellular stress substances,strain no.2 has advantages.(2)Through 64 hours cell culture of 9 kinds of yeast cells with different sugar concentrations of 40%,50% and 60%,it was found that the logarithmic growth period and delay period of the bacteria were prolonged with the increase of sugar concentration,and the growth curve was drawn to show that the growth of bacteria no.2 was excellent under different sugar concentrations.(3)The results of gas production in duchenne tubules after 24 hours of culture under different sugar concentrations showed that the gas production capacity of strain 2 was similar to that of other strains at 40% sugar concentration.With the increase of sugar concentration,bacteria strain no.1 and bacteria strain no.2 optimized and bred from industrial yeast were far better than other strains.(4)After a certain period of cell culture at different sugar concentrations,the cell morphology was observed in an electron microscope,and it was found that the integrity of cell structure of bacterium 2 was better than that of the other 8 yeasts at different sugar concentrations,followed by bacterium 1.(5)The actual fermentation results of the high-sugar dough showed that strain no.2 was superior to other strains in terms of gas production rate and gas holding capacity,which indirectly confirmed the experimental results of dufresne tubules.(6)Transcriptome analysis found that the trehalose and glycerol synthesis pathway in bacteria strain no.2 was additionally activated,and the relevant key genes were significantly up-regulated,indicating that the modification method of bacteria no.2 could make industrial baker's yeast better adapt to the hyperosmotic environment.