Mechanisms of Repair of Low Water Activity and pH-Injured Zygosaccharomyces rouxiiYSa40 in Glycerol and Sucrose/CPB Liquid Holding System

This study demonstrated injury of a 2-day-old stressed Zygosaccharomyces rouxiiYSa40 (Xerotolerant yeast) cells in 0.64water activity (a sub(w))/pH 3.5 glycerol (GLY)/CPB stress system. The effects of metabolic inhibitors on repair of the low a sub(w) injury were also investigated by resuscitating the low a sub(w) injured cells over a time period of 24 h in a suitably designed 0.87 a sub(w)/pH 3.5 GLY and sucrose (SUC)/citrate phosphate buffer (CPB) liquid holding (LH) system. On use of appropriate inhibitory concentrations of metabolic inhibitors, repair processes in low a sub(w)-injured populations involved cell membrane and cell wall synthesis, protein and DNA synthesis and adenosine triphosphate (ATP) from glycolysis, but without oxidative phosphorylation. During 24h of LH period, ATP was vital to maintain the cell viability of the surviving population on 0.94a sub(w)/pH 3.5 sugars/basal medium agar (lactic acid); while allowing its injured population to repair at low a sub(w) injury in the LH system. This oxidative phosphorylation pathway can provide insight into various mechanisms of repair in low a sub(w)-injured yeast cells. Practical Applications Results generated in this study are expected to benefit food industries where problems related to recovery of injured microbes are involved, especially in Intermediate Moisture Food products.