Petite mutation in aged and oxidatively stressed ale and lager brewing yeast

Abstract

Aims: To determine the role of oxidative stress and chronological ageing on the propensity of brewing yeast strains to form respiratory deficient ‘petites’. Methods and Results: Four industrial yeast strains (two ale and two lager strains) were exposed to oxidative stress in the form of H2O2 (5 mmol l−1) for two hours. Cell viability and occurrence of petites were determined by the slide culture and TTC‐overlay techniques, respectively. Increases in petite frequency were observed but only in those strains sensitive to oxidative stress. Chronological ageing under aerobic conditions led to an increase in petites in strains sensitive to oxidative stress. No such increase was observed under anaerobic conditions. Conclusion: Ageing may contribute to mitochondrial DNA damage and increase the propensity of brewing yeast cells to become respiratory deficient. Tolerant strains may be less likely to generate petites as a result of serial re‐pitching. Significance and Impact of the Study: Continuous re‐use of brewing yeast is associated with an increase in the frequency of petites within brewery yeast slurries, a phenomenon resulting in reduced fermentative capacity. The cause of petite generation during brewery handling is unknown. We show that endogenous oxidative stress has the potential to generate petites within brewing yeast populations.

Breeding of lager yeast with Saccharomyces cerevisiae improves stress resistance and fermentation performance

“…A relevant parameter for fermentation performance is the number of respiratory‐deficient ‘petite’ cells accumulated during fermentation, particularly when re‐using (repitching) yeasts for consecutive fermentations. These cells contribute to off‐flavour production and reduced fermentation (Gibson et al ., ). Remarkably, one of the BC strains generated in our study was significantly reduced in petite formation and also showed a higher survival rate at the end of fermentation.…”

Overexpression of DNA Polymerase Zeta Reduces the Mitochondrial Mutability Caused by Pathological Mutations in DNA Polymerase Gamma in Yeast

“…In addition, for heteroallelic strains containing dominant mutations, it is possible that replication stalling by mutant Mip1 itself causes oxidative damage on mtDNA, which can partially block replication by wt Mip1. Independently of the mechanisms, it is known that there is a correlation between mtDNA extended mutability and oxidative stress: petite frequency is higher in strains with a reduced antioxidant potential [66], in strains treated with hydrogen peroxide [67] and in strains deleted both in MSH1 and in OGG1 , encoding the mitochondrial glycosylase/lyase that specifically excises 8-oxo-dG residues in mtDNA [68].…”

Tolerance of pentose utilising yeast to hydrogen peroxide-induced oxidative stress

“…ROS can damage a variety of cellular components, including DNA, proteins and unsaturated lipids [11]. ROS can damage the mitochondria causing the formation of respiratory-deficient petites [12-14]. ROS has been shown to have a direct role in cellular aging [15], replicant life-span has been related to anti-oxidant potential of the cell and the number of re-pitches into a fermentation [16,17].…”