Volatile organic compounds mediated antifungal activity of Pichia and its effect on the metabolic profiles of fermentation communities.

Volatile Organic Compounds (VOCs) are chemicals responsible for antagonistic activity between microorganisms. The impact of VOCs on microbial community succession of fermentation is not well understood. In this study, Pichia were evaluated for VOCs production as a part of antifungal activity during Baijiu fermentation. Results showed that the abundance of Pichia in the defect group (agglomerated fermented grains) was lower than that in control group, and a negative interaction between Pichia and Monascus was determined (P < 0.05). In addition, the disruption of fungi was significantly related to the differences of metabolic profiles in fermented grains. To determine VOCs from Pichia and its effect on Monascus purpureus, a double-dishes system was assessed, and where the incidence of M. purpureus reduction was 39.22% after 7 days. As to antifungal volatile compounds, 2-phenylethanol was identified had effective antifungal effect on M. purpureus through contact and non-contact. To further confirm the antifungal activity of 2-phenylethanol, scanning electron microscopy showed that 2-phenylethanol widely and significantly inhibited conidia germination and mycelial growth of filamentous fungi. Metatranscriptomic analysis revealed that the Ehrlich pathway is the metabolic path of 2-phenylethanol in Pichia, and identified potential antifungal mechanisms that including protein synthesis and DNA damage. This study demonstrated the role of volatile-mediated microbial interaction in microbiome assembly and discovered a plausible scenario in which Pichia antagonized fungal blooms. The results may improve the niche establishment and growth of the functional yeast that enhances the flavor of BaijiuIMPORTANCE Fermentation of food occurs within communities of interacting species. The importance of microbial interactions in shaping microbial structure and metabolic performance to optimize the traditional fermentation process has long been emphasized, but the interaction mechanisms remain unclear. This study applied metabolome analysis and amplicon sequencing along with metatranscriptomic analysis to study the volatile-mediated antifungal activity of Pichia and its effect on the metabolism of ethanol during Baijiu fermentation, potentially enhancing the establishment of the fermentation niche and improving ethanol metabolism.