Yeast responses to stresses associated with industrial brewery handling: Figure 1

Abstract

During brewery handling, production strains of yeast must respond to fluctuations in dissolved oxygen concentration, pH, osmolarity, ethanol concentration, nutrient supply and temperature. Fermentation performance of brewing yeast strains is dependent on their ability to adapt to these changes, particularly during batch brewery fermentation which involves the recycling (repitching) of a single yeast culture (slurry) over a number of fermentations (generations). Modern practices, such as the use of high-gravity worts and preparation of dried yeast for use as an inoculum, have increased the magnitude of the stresses to which the cell is subjected. The ability of yeast to respond effectively to these conditions is essential not only for beer production but also for maintaining the fermentation fitness of yeast for use in subsequent fermentations. During brewery handling, cells inhabit a complex environment and our understanding of stress responses under such conditions is limited. The advent of techniques capable of determining genomic and proteomic changes within the cell is likely vastly to improve our knowledge of yeast stress responses during industrial brewery handling.

Carbohydrate utilization and the lager yeast transcriptome during brewery fermentation

“…The disaccharide trehalose, while historically viewed as a carbon and energy reserve (Fales, 1951), is now considered to function principally as a stress protectant and is known to have a role in protecting against the effects of a number of stresses (Francois and Parrou, 2001), including those associated with brewery-handling of yeast (Gibson et al, 2007). Of the genes involved in trehalose synthesis, only TPS1 demonstrated an increase in transcription (at 60 h), while TPS2 demonstrated a clear reduction in transcript levels throughout the sampling period.…”

Saccharomyces cerevisiae KNU5377 Stress Response during High-Temperature Ethanol Fermentation

“…The high toxicity of endogenously produced ethanol reduces cell viability, growth rate, and fermentation rate. Many mechanisms have been developed to help organisms withstand and/or prevent ethanol-induced damage during fermentation, including crossstress protection; yeast hybrids based on enological characterization (Belloch et al, 2008); membrane remodeling via changes in membrane (palmitoleic acid, oleic acid, and ergosterol) and cell wall composition (fatty acid, lipid, and isoprenoid metabolism); accumulation of amino acids (proline and tryptophan) and storage solutes (trehalose and glycogen) (Zhao and Bai, 2009); expression of molecular chaperones; transcriptional activation of V-ATPase and peroxisomal functions; enhancement of NADPH regeneration and redox balance (Cebollero et al, 2007;Ding et al, 2009;Orozco et al, 2012); genetic improvement through sexual cycle, parasexual hybridization and genetic engineering; and transcriptome remodeling of transcription factors, stress-related genes, and genes involved in signal transduction (Gibson et al, 2007;Ma and Liu, 2010a;Stanley et al, 2010). However, this approach has the intrinsic limitation that yeast adapts to different metabolic environments such as a high concentration of ethanol during fermentation.…”

Cleanup of industrial effluents containing heavy metals: a new opportunity of valorising the biomass produced by brewing industry

“…Before repitching, yeast cells are usually washed (with sterile water, food-grade quality acids, or with acid/ammonium persulfate) for removing any bacterial contaminants (Boulton and Quain 2001). The prac-tice of serial cropping and re-pitching imposes to yeast cells several stresses (such as oxidative, osmotic, ethanol, hydrostatic starvation, and cold shock), which influences the via-bility and vitality; this leads to obtaining slurries (high con-centrated cell suspension) with variable physiological con-ditions, which can originate inconsistent fermentation per-formance and affect the beer quality (Gibson et al 2007). Therefore, serial repitching is usually restricted to 7-20 fermentations; the number of serial re-pitchings depend on the strain robustness, company policy and production de-mands (Jenkins et al 2003;Powell et al 2003).…”