Isolation, characterization, and molecular identification of Saccharomyces strains from red dragon fruit peel (Hylocereus polyrhizus) for potential application in feed fermentation

Objectives: Red dragon fruit peel is a rich niche for indigenous yeasts with potential applications in feed fermentation. This study aimed to isolate, characterize, and molecularly identify Saccharomyces strains associated with red dragon fruit (Hylocereus polyrhizus) peel from An Giang province, Vietnam, and to assess their suitability as starter cultures for animal feed fermentation. Materials and Methods: A total of thirty yeast strains were isolated, of which 11 exhibited growth on YPDA medium supplemented with sodium bisulfite (NaHSO₃), suggesting sulfite tolerance. Morphological and biochemical characteristics were assessed, and ITS-based DNA sequencing was performed for molecular identification. Results: Six strains (CT6a, CT6b, CT6d, CT6g, CT3e, CT4a) showed high and stable biomass production and efficient fermentation performance in red dragon fruit peel extract. Sequence analysis confirmed all six as Saccharomyces cerevisiae with > 99% identity, and phylogenetic analysis further supported their clustering within the S. cerevisiae clade. Conclusions: Red dragon fruit peel represents a promising substrate for fermentation, and the identified native S. cerevisiae strains demonstrate strong potential as starter cultures in biotechnological applications, particularly for animal feed fermentation.