Screening Of Ammonium Sulfate Resistant Saccharomyces Cerevisiae And Its Mechanism

Saccharomyces cerevisiae is rich in methionine,lysine and other essential amino acid,which helps to improve the nutritional value of feed and meet the needs of animals for protein.Moreover,S.cerevisiae fermentation can produce alcohol and carbon dioxide,which helps to improve the aroma and taste of feed.Therefore,S.cerevisiae plays an important role in the production of protein feed industry.However,in industrial production processes,high concentrations of ammonium sulfate have an inhibitory effect on yeast growth,leading to a decrease in the production efficiency of protein in feed.Therefore,it is of great practical significance to screen wild yeast strains resistant to ammonium sulfate through ammonium sulfate plate.In this study,ammonium sulfate resistant S.cerevisiae was obtained through strain breeding,which provides a new idea for the breeding of ammonium sulfate resistant yeast.At the same time,the mechanism of its ammonium sulfate resistance was analyzed,providing a certain reference and theoretical reference for the targeted transformation of ammonium sulfate resistant S.cerevisiae.In this study,soil and fruit samples were used as screening sources,194 strains of yeast were obtained through primary screening of Bengal Red medium,and 15 strains of yeast were obtained through re screening of WL medium.Through morphological observation,physiological and biochemical experiments and molecular biological identification,15 strains of yeast were identified as S.cerevisiae.Secondly,S.cerevisiae Z-1 and S.cerevisiae Z-3 were screened through the ammonium sulfate resistance experiment.S.cerevisiae Z-1 had larger and fuller colonies in the presence of 1.0 mol/L NH₄⁺（6.6%（NH₄）₂SO₄（w/v））.The growth curve and protein content of S.cerevisiae Z-1were determined to be ammonium sulfate resistant.Under ammonium sulfate stress,the cell morphology of S.cerevisiae Z-1 was changed compared with the laboratory standard strain,and the cell wall components were changed.Under ammonium sulfate stress,the contents of Trehalose and intracellular and extracellular glycerol fluctuated,and with the increase of ammonium sulfate concentration,the contents of Trehalose and intracellular and extracellular glycerol appeared peaks at different time points and showed a trend of first rising and then declining.Finally,through Sequence alignment analysis of ammonium sulfate resistance related genes,it was found that opi3,sho1,srl1,elo2 and hog1 genes in S.cerevisiae Z-1 involved14 base mutations,of which four base mutations in hog1 gene did not lead to amino acid changes,and two base mutations in pis1 gene did not lead to amino acid changes.The relative expression test showed that the expression of genes related to ammonium sulfate resistance in S.cerevisiae Z-1 was significantly increased,so it was concluded that the change of expression of genes related to ammonium sulfate resistance was an important factor affecting the resistance of S.cerevisiae to ammonium sulfate.