Yeast mycobiome of fruit and vegetable biowastes revealed by culture-dependent and metabarcoding approaches: Screening for the production of succinic acid and single cell oils

Fruit and vegetable by-products and agro-residues from food processing industries and households negatively impact the environment, economy, and society. Yeasts are metabolically efficient at converting food wastes into value-added products such as biopeptides, single-cell oils, single-cell proteins, and organic acids. This work explores the valorization of twelve fruit and vegetable-derived wastes as inexpensive substrates for obtaining high-value products and metabolically efficient yeasts. Culture-dependent and metabarcoding methods provided a comprehensive overview of the yeast mycobiome, revealing 33 common species. From a biobank of 252 isolates obtained from the twelve biowastes, the 31 most promising isolates were evaluated using a synthetic medium that mimicked fruit and vegetable waste. The results showed that the metabolism was mainly directed towards the Krebs cycle, with lower production of single-cell oil compared to organic acids. Kazachstania humilis stood out from the general metabolic heterogeneity, producing 0.9 g/L of succinic acid and 1.4 g/L of acetic acid. Our results demonstrate that these natural isolates can produce high-value compounds at levels comparable to those obtained under optimal conditions for yeast growth.