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Studies on food spoiler yeasts, recognized Zygosaccharomyces, Debaryomyces, and Yarrowia as commercial players referring their biochemistry and food spoilage activities. However, the impact of salinity on physiology and biochemical traits is largely unknown in leading organoleptic halotolerant yeast Zygosaccharomyces bisporus. Interestingly, within 1 h in vitro sub-lethal salt stress in Z. bisporus MTCC 4801, a considerable variation in growth was visible in early phase (minimum cell viability) synchronically with observed (P<0.05) reduced biomass yield, intracellular glutathione content, and K⁺/Na⁺ ratio. Immediate glutathione depletion addresses its essentiality in scavenging reactive species attributable to overlap between osmotic and oxidative stresses initiated under salinity. Though prolonged 2 h stress duration ameliorated these reductions together with rapid efflux of toxic sodium ions, which strongly suggest that Na⁺ in Z. bisporus is toxic and strategically excluded, while cellular GSH performs growth restoration preparing metabolic systems to be high salt-resistant. From the lipid profiling studies, we further confirmed consequential lipid alterations contribute to higher membrane fluidity. Hence, assist the cells in osmo-adaptation against deleterious effects of NaCl allied to expulsion of Na⁺ ions and GSH protection. These data have an agricultural and food industrial application in assessing the spoilage potential of new/ existing fermented product formulations.

Key words: Food spoilage; Salt stress; K⁺/Na⁺ ratio; Growth and biomass yield; GSH.