Revealing Non-Conventional and Thermotolerant Yeasts from Tropical Regions: Diversity and Potential Traits for Bioproducts

The diminishing reserves of fossil fuels have spurred a global search for sustainable energy alternatives. Bioethanol, a renewable fuel derived from biomass, represents a promising alternative, particularly in tropical regions. Yeasts, key agents in ethanol fermentation, have attracted substantial attention for their ability to convert sugars into ethanol. However, the commonly used mesophilic yeast <i>Saccharomyces cerevisiae</i> is temperature-sensitive, limiting its effectiveness in tropical climates. Tropical countries such as Indonesia, Thailand, Vietnam, and Laos, harbor abundant non-conventional and thermotolerant yeast species. These yeasts offer multiple advantages, including reduced contamination risk, lower cooling requirements, and decreased production costs. Moreover, they can utilize complex substrates, such as sucrose, starch, xylose, and lignocellulose biomass, while tolerating high temperatures, ethanol stress, pH fluctuations, and various inhibitors. This review highlights the diversity, physiological traits, and dual industrial potential of thermotolerant and non-conventional yeasts isolated from tropical environments. These yeasts demonstrate robust substrate utilization (including pentoses), high-temperature tolerance, and resilience under stress, positioning them as promising candidates for second-generation bioethanol production as well as for producing value-added aroma compounds. Key species discussed include <i>Ogataea polymorpha, Candida tropicalis, Kluyveromyces marxianus, Pichia kudriavzevii, Meyerozyma caribbica, Pichia stipitis, and Spathaspora passalidarum.</i>