Effects Of Snf1 Protein Kinase Subunits On Maltose Metabolism In Baker's Yeast

Maltose is the primary fermentable sugar in flour,so maltose utilization of baker's yeast is the key factor in lean dough leavening.The glucose repression is one of the most important factors effecting the maltose fermentation ability,while the Snfl protein kinase is a key enzyme releasing glucose repression.The regulation of Snfl protein kinase subunits for maltose metabolism of baker's yeast was studied and the main research contents and results are as follows:(1)The SNF1 gene,encoding Snfl protein kinase ? subunit in baker's yeast,was deleted and overexpressed to obtain a gene knockout strain B-SNF1 and overexpression strain B+SNF1.Low sugar model liquid dough(LSMLD)medium fermentation results showed that compared with the parental strain BY14?,the sugar utilization efficiency of B+SNF1 strain increased by 2.9%,11%and 18%in three LSMLD medium(glucose,maltose and glucose-maltose),respectively.While the maltose utilization efficiency of B-SNF1 Strain in maltose and glucose-maltose LSMLD medium reduced by 10%and 11%than the parental strain BY14?.Lean dough fermentation results showed that compared with the parental strain the strain B+SNF1 produced 85 mL more CO2 for 60 min and the fermentation time shortened by 11%and the leavening ability increased by 15%,by contrast,the strain B-SNF1 decreased the CO2 production from 700 mL to 600 mL and the leavening ability decreased by 13%and prolonged fermentation time for 10 min compared with the parental strain.(2)The SNF4 gene and GAL83 gene,encoding Snfl protein kinase ? subunit and ?subunit in baker's yeast,were overexpressed respectively to obtain overexpression strains B+SNF4 and B+GAL83.LSMLD medium fermentation results showed that compared with the parental strain BY14?,the sugar utilization efficiency of B+SNF4 strain increased by 1.4%,7.1%and 1.4%in three LSMLD medium(glucose,maltose and glucose-maltose),respectively.While the maltose utilization efficiency of the B+GAL83 Strain decreased by 1.3%,4.1%and 32.6%in three LSMLD medium than parental strain,respectively.Lean dough fermentation results showed that compared with the parental strain the strain B+SNF4 produced 60 mL more CO2 for 60 min and the fermentation time shortened by 5 min and the leavening ability increased by 12.7%,by contrast,the strain B+GAL83 decreased the CO2 production from 700 mL to 620 mL and the leavening ability decreased by 5.3%and prolonged fermentation time for 5 min compared with the parental strain.(3)The SNF1 and SNF4 gene were overexpressed simultaneously to obtain double gene overexpression strain B+SNF1+SNF4.The SNF1?SNF4 and GAL83 gene were overexpressed simultaneously to obtain strain B+SNF1+SNF4+GAL83.LSMLD medium fermentation results showed that compared with the parental strain BY14a,the sugar utilization efficiency of B+SNF1+SNF4 strain increased by 3.4%,12.2%and 17.5%in three LSMLD medium(glucose,maltose and glucose-maltose),respectively.Lean dough fermentation results showed that compared with the parental strain the strain B+SNF1+SNF4 produced 95 mL more CO2 for 60 min and the fermentation time shortened by 15 min and the leavening ability increased by 17.8%.However,The B+SNF1+SNF4+GAL83 strain showed no significant differences with the parental strain.The results show that the a subunit and ? subunit played a major role in the impact of Snfl protein kinase on baker's yeast maltose metabolism.The results lay a good foundation for building "quick" baker's yeast strains.