Expression Patterns of Mal genes and its Association with Differential Maltose and Maltotriose Transport rate of Two Saccharomyces pastorianus Yeasts

Microorganisms play a significant role in fermented food biotechnology by converting raw materials in human edible organoleptic and nutritive components, especially in the beer brewing industry. The lager-style beer is the dominant industrial beer type, and it is fermented by Saccharomyces pastorianus (Sp) whose members encompass two groups. Typically, strains belonging to group I are deficient in maltotriose consumption. The main variables linked to this phenotype are fermentation conditions, the presence of maltotriose transporters, copy number variation of maltose and maltotriose transporters, and differential genetic regulation. This study was aimed to determine that the differences the alpha-glycoside consumption phenotypes of two Sp strains, Sp820 and Sp790, are related with different phylogenetic distribution and gene expression of the transporters ScMalx1, SeMalx1, ScAGT1, SeAGT1, MTT1 and MPHx. Biochemical analyses of the transport rate confirmed that the Sp790 strain transported more maltose and maltotriose, 28% and 32% respectively, than Sp820 strain. In addition, detection of Sp790 transcripts indicated the presence of all the Mal genes analyzed since the first day of fermentation, whereas Sp820 only presented transcripts for the ScMalx1, ScAGT1, and MPHx genes. These results indicate that a multifactorial phenomenon related with phylogenetic distribution, polymorphisms in transmembrane domains and the difference in the genetic expression of maltose and maltotriose transporters are involved in the phenotypic diversity related with maltose and maltotriose consumption in two lager yeast.