Monitoring Stress-Related Genes during the Process of Biomass Propagation of Saccharomyces cerevisiae Strains Used for Wine Making

Abstract

Physiological capabilities and fermentation performance of Saccharomyces cerevisiae strains to be employed during industrial wine fermentations are critical for the quality of the final product. During the process of biomass propagation, yeast cells are dynamically exposed to a mixed and interrelated group of known stresses such as osmotic, oxidative, thermic, and/or starvation. These stressing conditions can dramatically affect the parameters of the fermentation process and the technological abilities of the yeast, e.g., the biomass yield and its fermentative capacity. Although a good knowledge exists of the behavior of S. cerevisiae under laboratory conditions, insufficient knowledge is available about yeast stress responses under the specific media and growth conditions during industrial processes. We performed growth experiments using bench-top fermentors and employed a molecular marker approach (changes in expression levels of five stress-related genes) to investigate how the cells respond to environmental changes during the process of yeast biomass production. The data show that in addition to the general stress response pathway, using the HSP12 gene as a marker, other specific stress response pathways were induced, as indicated by the changes detected in the mRNA levels of two stress-related genes, GPD1 and TRX2. These results suggest that the cells were affected by osmotic and oxidative stresses, demonstrating that these are the major causes of the stress response throughout the process of wine yeast biomass production.

Recent Advances in Yeast Biomass Production

“…The molecular responses of laboratory S. cerevisiae strains to different stresses have been thoroughly studied, and a large body of knowledge is available (Gasch and Werner-Washburne, 2002;Hohmann and Mager, 2003). In addition, several approaches for the characterisation of stress responses under industrial conditions have been carried out for wine and lager yeasts (Pérez-Torrado et al, 2005;Gibson et al, 2007), and some correlations have been found between stress resistance of several yeast strains and their suitability for industrial processes (Beudeker et al, 1990;Ivorra et al, 1999;Aranda et al, 2002;Pérez-Torrado et al, 2002;Zuzuarregui et al, 2005;Pérez-Torrado et al, 2009;Gómez-Pastor et al, 2010a). For these reasons, the study of stress responses under industrial conditions has become an important research field to improve our knowledge of not only complex industrial processes, but of yeast capabilities.…”

“…They have all been designed to mainly analyse the fed-batch phase without considering the whole process. The first published study on the complete industrial process was the simulation of wine yeast biomass propagation by performing batch and fed-batch phases in only one bioreactor (Pérez-Torrado et al, 2005). This simplification of the process enabled the study of yeast physiology from a molecular point of view with a bench-top design ( Fig.…”

“…Studies of brewing yeast under industrial fermentations have demonstrated the suitability of the marker gene expression as a tool to study yeast stress responses in industrial processes (Higgins et al, 2003a). Monitoring stress-related marker genes, such as HSP12, GPD1, STI1, GSY2 and TRX2, www.intechopen.com during bench-top growth trials of wine yeast biomass propagation have demonstrated that osmotic (GPD1) and oxidative stresses (TRX2) are the main adverse conditions that S. cerevisiae senses during this process (Pérez-Torrado et al, 2005). Afterwards, a genome-wide expression analysis of the same process established stress-critical time points throughout the process based on the profiles of different oxidative stress response genes (Gómez-Pastor et al, 2010b).…”

“…In recent years, a substantial effort has been made to gain insight into yeast responses during the process. It was believed that industrial conditions were optimised to obtain the best performing yeast cells, but now we know that yeast cells endure several stressful situations that induce multiple intracellular changes and challenge their technological fitness (Attfield, 1997;Pretorius, 1997;Pérez-Torrado et al, 2005). With wine yeast, moreover, the biomass is concentrated and dehydrated at the end of the process to obtain ADY yeasts that can be stored for long periods of time (Degre, 1993).…”

“…(Garre et al, 2010). As a result, these dynamic environmental injuries seriously affect biomass yield, fermentative capacity, vitality, and cell viability (Attfield, 1997;Pretorius, 1997;Pérez-Torrado et al, 2005;Pérez-Torrado et al, 2009). …”