Recent developments in the biology and biotechnological applications of halotolerant yeasts

Natural hypersaline environments are inhabited by an abundance of prokaryotic and eukaryotic microorganisms capable of thriving under extreme saline conditions. Yeasts represent a substantial fraction of halotolerant eukaryotic microbiomes and are frequently isolated as food contaminants and from solar salterns. During the last years, a handful of new species has been discovered in moderate saline environments, including estuarine and deep-sea waters. Although Saccharomyces cerevisiae is considered the primary osmoadaptation model system for studies of hyperosmotic stress conditions, our increasing understanding of the physiology and molecular biology of halotolerant yeasts provides new insights into their distinct metabolic traits and provides novel and innovative opportunities for genome mining of biotechnologically relevant genes. Yeast species such as Debaryomyces hansenii, Zygosaccharomyces rouxii, Hortaea werneckii and Wallemia ichthyophaga show unique properties, which make them attractive for biotechnological applications. Select halotolerant yeasts are used in food processing and contribute to aromas and taste, while certain gene clusters are used in second generation biofuel production. Finally, both pharmaceutical and chemical industries benefit from applications of halotolerant yeasts as biocatalysts. This comprehensive review summarizes the most recent findings related to the biology of industrially-important halotolerant yeasts and provides a detailed and up-to-date description of modern halotolerant yeast-based biotechnological applications.