The Oxidative Stress Response of a Lager Brewing Yeast Strain during Industrial Propagation and Fermentation

Commercial brewing yeast strains are exposed to a number of potential stresses including oxidative stress. The aim of this investigation was to measure the physiological and transcriptional changes of yeast cells during full-scale industrial brewing processes with a view to determining the environmental factors influencing the cells oxidative stress response. Cellular antioxidant levels were monitored throughout an industrial propagation and fermentation and microarray analysis was employed to determine transcriptional changes in antioxidant-encoding and other stress response genes. The greatest increase in cellular antioxidants and transcription of antioxidant-encoding genes occurred as the rapidly fermentable sugars glucose and fructose were depleted from the growth medium (wort) and the cell population entered the stationary phase. The data suggest that, contrary to expectation, the oxidative stress response is not influenced by changes in the dissolved oxygen concentration of wort but is initiated as part of a general stress response to growth-limiting conditions, even in the absence of oxygen. A mechanism is proposed to explain the changes in antioxidant response observed in yeast during anaerobic fermentation. The results suggest that the yeast cell does not experience oxidative stress, per se, during industrial brewery handling. This information may be taken into consideration when setting parameters for industrial brewery fermentation.

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Gibson BR, Lawrence SJ, Boulton CA, Box WG, Graham NS, Linforth RS, Smart KA