Harnessing Osmotolerant Yeasts for Advanced Food Fermentation and Bioprocessing: From Molecular Mechanisms to Industrial Implementation

Osmotolerant yeasts are essential biocatalysts in food biotechnology, uniquely equipped to thrive in high-solute environments that inhibit the growth of most microorganisms. This review offers a detailed overview of the molecular foundations of this resilience, with a particular focus on the conserved High-Osmolarity Glycerol (HOG) pathway. The manuscript clarifies how this signaling cascade, triggered by sensors Sln1 and Sho1, activates the Hog1 kinase, orchestrating a transcriptional response that regulates both glycerol synthesis (GPD1, GPP2) and retention (Fps1, Stl1) for cellular osmoregulation. Understanding this fundamental mechanism has important industrial applications, as both native and engineered strains of Saccharomyces cerevisiae and Zygosaccharomyces rouxii improve the efficiency and quality of fermentations for products such as bioethanol, soy sauce, ice wine, and high-sugar doughs, thereby improving yields, fermentation kinetics, and sensory profiles. This review also explores how non-Saccharomyces yeasts contribute to flavor complexity and their role in bioremediating saline waste streams. Furthermore, this work highlights innovative strategies, such as Adaptive Laboratory Evolution (ALE) for robust phenotype selection and CRISPR-Cas9 for precise metabolic engineering, to create advanced yeast cell factories. By integrating molecular mechanisms with biotechnological innovations, this work underscores the significance of osmotolerant yeasts in enhancing sustainability and efficiency in the food industry.