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.