Construction Of Baker's Yeast For Quick Fermentation

Maltose is the most important fermented sugar in the flour,in addition to a small amount of glucose,fructose and other fermentable sugars.Therefore,the utilization rate of maltose is a key factor affecting the rapid fermentation of dough.And the glucose repression is the main limiting factor in maltose utilization,so the removal of glucose repression is an effective way to improve the level of maltose utilization.In this paper,we studied the effect of genes that are direct related to maltose metabolism and the ? subunit of Snfl protein kinase on the regulation of maltose metabolism.The main research contents are as follows:(1)Based on the study of our laboratory,the industrial baker's yeast strain BY14 and its haplotypes BY 14-17a and BY14-70a were selected as the parent strains,we obtained the mutant strains B-S+S,17a-S+S,70a-S+S by knocking out the repressor gene SSN6 and overexpression the positive regulate genes SNF1.The results of fermentation in lean dough showed that:The CO2 production of 17a-S+S reached 710 mL in 1h,the fermentation time was shortened by 15%and the fermentation power was increased by 39%.Low sugar model liquid dough(LSMLD)medium fermentation results showed that:Compared with the parental strain BY 14a,the maltose utilization ability of 17a-S+S was increased by 8.2%and 10%respectively in the two medium(maltose,mixed sugar).(2)The industrial baker's yeast strain BY14 and its haplotypes BY14-17a and BY14-70a were selected as the parent strains,respectively,we obtained the mutant strains:B-S+M,17a-S+M,70a-S+M by knocking out the repressor gene SSN6 and overexpression the positive regulate genes MAL62.The results of fermentation in lean dough showed that only 17a-S+M fermentation performance was significantly improved.The CO2 production of 17a-S+M could reach 690 mL in 1 h,compared with the parental strain BY14a,which was 165mL higher,the fermentation time was shortened by 15%and the fermentation power was increased by 35%.Low sugar model liquid dough(LSMLD)medium fermentation results showed that:Compared with the parental strain BY14a,the maltose utilization capacity of 17a-S+M was increased by 8.2%and 7.2%,respectively,in the two medium(maltose,mixed sugar);(3)The constructed mutant strain 17a-S+S was crossed with 70a-S+M to obtain the diploid recombinant strain B-S+MS that knocked out SSN6 while overexpressing SNF1 and MAL62.The results showed that the dough fermentation efficiency of B-S+MS was increased by 18.6%compared with the parent strain;(4)Overexpression the genes SIP1 and SIP2,which encode the P subunit of Snfl protein kinase,respectively,and obtained the recombinant strains 17a+SIP 1,17a+SIP2.And fermented with B+GAL83 to analysis the role of P subunit in the baker yeast maltose metabolism.The results showed that the overexpression of SIP1 and SIP2 had no significant effect on the maltose utilization of baker's yeast,and the overexpression of GAL83 reduced the fermentation power of dough and the maltose metabolic capacity.