The ability to accumulate tyramine and 2-phenylethylamine by two strains of Enterococcus faecalis and two strains Enterococcus faecium was evaluated in two cultural media added or not with tyrosine. All the enterococcal strains possessed a tyrDC which determined tyramine accumulation in all the conditions tested, independently on the addition of high concentration of free tyrosine. Enterococci differed in rate and level of biogenic amines accumulation. E. faecalis EF37 and E. faecium FC12 produced tyramine in high amount since the exponential growth phase, while 2-phenylethylamine was accumulated when tyrosine was depleted. Enterococcus faecium FC12 and E. faecalis ATCC 29212 showed a slower tyraminogenic activity which took place mainly in the stationary phase up to 72 h of incubation. Moreover, E. faecalis ATCC 29212 produced 2-phenylethylamine only in the media without tyrosine added. In BHI added or not with tyrosine the tyrDC gene expression level differed considerably depending on the strains and the growth phase. In particular, the tyrDC gene expression was high during the exponential phase in rich medium for all the strains and subsequently decreased except for E. faecium FC12. Even if tyrDC presence is common among enterococci, this study underlines the extremely variable decarboxylating potential of strains belonging to the same species, suggesting strain-dependent implications in food safety.

Kombucha is a fermented tea with a long history of production and consumption. It has been gaining popularity thanks to its refreshing taste and assumed beneficial properties. The microbial community responsible for tea fermentation—acetic acid bacteria (AAB), yeasts, and lactic acid bacteria (LAB)—is mainly found embedded in an extracellular cellulosic matrix located at the liquid–air interphase. To optimize the production process and investigate the contribution of individual strains, a collection of 26 unique strains was established from an artisanal-scale kombucha production; it included 13 AAB, 12 yeasts, and one LAB. Among these, distinctive strains, namely Novacetimonas hansenii T7SS-4G1, Brettanomyces bruxellensis T7SB-5W6, and Zygosaccharomyces parabailii T7SS-4W1, were used in mono- and co-culture fermentations. The monocultures highlighted important species-specific differences in the metabolism of sugars and organic acids, while binary co-cultures demonstrated the roles played by bacteria and yeasts in the production of cellulose and typical volatile acidity. Aroma complexity and sensory perception were comparable between reconstructed (with the three strains) and native microbial consortia. This study provided a broad picture of the strains’ metabolic signatures, facilitating the standardization of kombucha production in order to obtain a product with desired characteristics by modulating strains presence or abundance.

Metschnikowia pulcherrima is increasingly valued in sustainable vitiviniculture for its dual role as a biocontrol agent and as a contributor to wine quality. However, a coordinated dual-purpose selection strategy has not yet been systematically implemented for this species. This study aimed to identify native strains with combined wine-related traits and biocontrol potential by screening a collection of 179 isolates for key phenotypic traits—β-glucosidase and β-lyase activities, hydrogen sulfide (H₂S) production, and pulcherrimin biosynthesis—and assessing their genotypic diversity. Dereplication yielded 106 unique strains, from which five with the most favorable wine-related traits and distinct genotypic profiles were selected for subsequent evaluation of antagonistic potential. Safety-related traits, including growth at 37 °C, invasive growth, pseudohyphal formation, and proteolytic activity, were assessed to exclude virulence-associated behaviors. Antagonistic activity against Botrytis cinerea was evaluated through in vitro dual-culture assays and in vivo grape-berry inoculations, revealing strain- and pathogen-dependent inhibition, with volatile-mediated effects generally exceeding direct-contact interactions. Among the tested strains, NLSFS4 showed strong and consistent biocontrol potential. Microvinification trials further confirmed its oenological relevance, demonstrating the ability to modulate wine aroma composition while preserving fermentation performance. Overall, this study highlights the substantial functional diversity within M. pulcherrima and identifies a promising native strain for integrated use in wine fermentation and biological control in sustainable production systems.