title: Enhanced freeze tolerance of baker's yeast by overexpressed trehalose-6-phosphate synthase gene (TPS1) and deleted trehalase genes in frozen dough.
abstract: Several recombinant strains with overexpressed trehalose-6-phosphate synthase gene (TPS1) and/or deleted trehalase genes were obtained to elucidate the relationships between TPS1, trehalase genes, content of intracellular trehalose and freeze tolerance of baker's yeast, as well as improve the fermentation properties of lean dough after freezing. In this study, strain TL301(TPS1) overexpressing TPS1 showed 62.92 % higher trehalose-6-phosphate synthase (Tps1) activity and enhanced the content of intracellular trehalose than the parental strain. Deleting ATH1 exerted a significant effect on trehalase activities and the degradation amount of intracellular trehalose during the first 30 min of prefermentation. This finding indicates that acid trehalase (Ath1) plays a role in intracellular trehalose degradation. NTH2 encodes a functional neutral trehalase (Nth2) that was significantly involved in intracellular trehalose degradation in the absence of the NTH1 and/or ATH1 gene. The survival ratio, freeze-tolerance ratio and relative fermentation ability of strain TL301(TPS1) were approximately twice as high as those of the parental strain (BY6-9α). The increase in freeze tolerance of strain TL301(TPS1) was accompanied by relatively low trehalase activity, high Tps1 activity and high residual content of intracellular trehalose. Our results suggest that overexpressing TPS1 and deleting trehalase genes are sufficient to improve the freeze tolerance of baker's yeast in frozen dough. The present study provides guidance for the commercial baking industry as well as the research on the intracellular trehalose mobilization and freeze tolerance of baker's yeast.
authors.affiliation: Tianjin Industrial Microbiology Key Laboratory, College of Biotechnology, Tianjin University of Science and Technology, Tianjin, 300457, People's Republic of China, haigang1998@163.com.
authors.forename: Haigang
authors.initials: H
authors.lastname: Tan
authors.forename: Jian
authors.initials: J
authors.lastname: Dong
authors.forename: Guanglu
authors.initials: G
authors.lastname: Wang
authors.forename: Haiyan
authors.initials: H
authors.lastname: Xu
authors.forename: Cuiying
authors.initials: C
authors.lastname: Zhang
authors.forename: Dongguang
authors.initials: D
authors.lastname: Xiao
mesh_terms: D000064:Acclimatization / Q000235:genetics / Q000502:physiology*; D005285:Fermentation; D019649:Food Industry; D005615:Freezing; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal / Q000235:genetics / Q000502:physiology*; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D013045:Species Specificity; D014198:Trehalase / Q000235:genetics; D014199:Trehalose / Q000378:metabolism
chemical_list: D029701:Saccharomyces cerevisiae Proteins; D014199:Trehalose; D005964:Glucosyltransferases; C023180:trehalose-6-phosphate synthase; D014198:Trehalase