Monitoring of the production of flavour compounds by analysis of the gene transcription involved in higher alcohol and ester formation by the brewer's yeast Saccharomyces pastorianus using a multiplex RT-qPCR assay

Lager yeast produces a broad range of aroma-active substances during fermentation, of which higher alcohols and volatile esters are vital for the complex flavour of beer. Lager yeast contains several genes that encode the proteins responsible for flavour production. Investigation of gene expression in the hybrid Saccharomyces pastorianus is meaningful as it combines genes from both S. cerevisiae (Sc-type) and S. bayanus (Sb-type). In this study, we developed a GeXP analyser-based multiplex polymerase chain reaction assay to simultaneously assess the transcription of BAP2, BAT1, BAT2, ATF1, ATF2, EEB1, EHT1 and IAH1, involved in higher alcohol and volatile ester biosynthesis, within the S. pastorianus genome from both sub-genomes. GeXP proved to be an effective method of performing a gene expression study by providing a continuous profile of the expression of multiplex genes. This offers the possibility of using this type of data to monitor and control fermentations. Profiles of higher alcohol and volatile ester formation, and the transcription of specific genes, indicated that the synthesis of flavour compounds appears to correlate, at least in part, to the transcription of certain genes. As well as the differential expression of various genes, the differential expression of orthologous genes was also observed during fermentation, suggesting that the Sc-type and Sb-type genes may have different functions. Our results will further the understanding and manipulation of the phenotype of commercially important lager yeasts. Copyright (c) 2014 The Institute of Brewing & Distilling