Metabolic Screening of Native Metschnikowia Strains for Growth on Agroindustrial Residues and Biocontrol of Verticillium sp. in a Sustainable Production Framework

The agricultural sector generates substantial waste that harms both the environment and human health. This study aimed to utilise Metschnikowia yeasts to convert native agricultural wastes without chemical pretreatment. Ten Metschnikowia isolates were assessed using API tests to identify their assimilation profiles and enzymatic activities. Yeast growth was evaluated via the plate count method. The culture media containing molasses, brewery spent grain, and postharvest sunflower parts were characterised chromatographically, and the in vitro impact on Verticillium tenerum phytopathogen was evaluated. The effect of the yeast preparations on Caco-2, IEC-6, and HaCaT cell lines was also investigated. Solid waste materials without preliminary chemical pretreatment supported yeast multiplication to 4.5 × 107–1.3 × 108 CFU/mL. The metabolite composition and enzymatic activity of lipase, glucosidase, and protease in post-culture media suggest that they may act as growth inhibitors of the Verticillium strain. For post-cultivation samples, inhibition coefficients were equal to 1.24–2.00, depending on the kind of substrate and yeast strain used. Antimicrobial activity was also noted in cell-free samples after yeast cultivation on sunflower stalks and brewery spent grain. The toxicological analysis showed that the yeast preparations did not cause toxic effects on the tested cell lines. This research offers a sustainable approach using Metschnikowia yeasts, highlighting the importance of a holistic method that combines microbiological, biochemical, and toxicological aspects for sustainable waste management and the development of new applications, such as feed supplements and biocontrol agents.