Terpenoid biosynthesis in yeasts: metabolic diversity and opportunities for food fermentation.

Terpenoids are key contributors to aroma in fermented foods and beverages, yet yeast has traditionally been considered a poor source of de novo monoterpenes. Increasing evidence shows that fermentative yeasts possess an intrinsic capacity to produce volatile isoprenoids through the native mevalonate pathway in the absence of plant precursors. Central to this metabolic plasticity is the prenyltransferase Erg20p, which regulates the balance between geranyl diphosphate (GPP) and farnesyl diphosphate. Variations in ERG20 structure and kinetics can enhance GPP availability, enabling monoterpene formation via metabolic 'leakage', as previously observed for geraniol production. In parallel, several yeast species naturally produce sesquiterpenes such as farnesol and nerolidol. These insights highlight new opportunities to exploit yeast metabolic diversity through non-GMO (Genetic Modified Organisms) strategies for terpene-driven flavor innovation in food fermentations.