Mechanisms of Repair of Low Water Activity and pH-Injured Z ygosaccharomyces rouxii YSa40 in Glycerol and Sucrose/CPB Liquid Holding System

Abstract

This study demonstrated injury of a 2-day-old stressed Zygosaccharomyces rouxii YSa40 (Xerotolerant yeast) cells in 0.64 water activity (aw)/pH 3.5 glycerol (GLY)/CPB stress system. The effects of metabolic inhibitors on repair of the low aw injury were also investigated by resuscitating the low aw injured cells over a time period of 24 h in a suitably designed 0.87 aw/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 aw-injured populations involved cell membrane and cell wall synthesis, protein and DNA synthesis and adenosine triphosphate (ATP) from glycolysis, but without oxidative phosphorylation. During 24 h of LH period, ATP was vital to maintain the cell viability of the surviving population on 0.94 aw/pH 3.5 sugars/basal medium agar (lactic acid); while allowing its injured population to repair at low aw injury in the LH system. This oxidative phosphorylation pathway can provide insight into various mechanisms of repair in low aw-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.