Differential Yeast Gene Transcription during Brewery Propagation

Abstract

The aim of this study was to determine the transcriptomic response of Saccharomyces pastorianus to environmental change during brewery propagation. Utilization of amino acids and fermentable carbohydrates during fullscale brewery propagation was compared with the simultaneous changes occurring in the yeast transcriptome. Results showed that transcription profiles fell within one of four groups, and the greatest changes occurred within the first 8 hr following inoculation. Nutrient uptake was at its greatest during this period, and many genes involved in the utilization of amino acids and carbohydrates were activated. There was also a significant derepression response following monosaccharide exhaustion. A number of stress-response genes were activated following inoculation, indicating a possible osmotic stress response. Nutrient limitation did not appear to initiate a significant stress response but did activate genes involved in pseudohyphal growth and meiosis, despite the fact that neither biological process occurs in the strain utilized. The first hours after inoculation into propagation wort were particularly active with respect to nutrient utilization and transcriptional change. It is likely that this period was particularly stressful for yeast cells, although there was no evidence of viability loss, and it may be concluded that yeast cells can cope with this level of stress, possibly aided by the dynamic response of the transcriptome.