Genomic and phenotypic analysis of stress-tolerant, aroma-producing yeast screened under low-a_w, low-moisture content...

Developing low-salt foods is crucial to address health concerns associated with hsigh-salt diets, yet it poses a technical challenge: supporting microbial control through low water activity (a_w) regulation without high-salt concentrations requires reducing the moisture content of the substrate, which poses a physiological challenge to conventional fermentative microbes. This study aims to bridge this gap by isolating yeasts capable of thriving under such low-salt (4-12% dry basis, d.b.), low-a_w (0.87-0.92), and low-moisture content conditions. Using controlled fermentation of two chili varieties as a model system, we analyzed microbial community succession and its correlation with volatile flavor profiles. A total of 72 indigenous yeasts were isolated via multi-stage phenotypic screening. The dominant strain, M13, exhibited superior aroma-producing capability, yielding 1.32 g/kg of total esters, and pronounced tolerance to key fermentation stresses, including low pH (2.0), high ethanol (9%), and growth retention at the fermentation temperature of 40 °C. Whole-genome sequencing and functional annotation suggested that these phenotypic traits were associated with a genomic architecture enriched in metabolic and stress-responsive functions, including a 12.97 Mbp genome in which 54.5% of annotated genes were assigned to metabolic categories. This integrated study provides a novel functional yeast candidate and a screening framework that may help improve the balance between flavor quality and microbial control in low-salt fermentation. This approach and the microbial principles highlighted here may be applicable to the development of a wider range of flavorful, reduced‑sodium fermented products, offering a potential route to reduce reliance on both added salts and high-water content in food fermentation.