Valorisation of olive pomace and tomato by-products with selected yeasts strains

Food industries produce high amounts of by-products, wastes and residues which are considered a problem because they contribute to environmental pollution. On the other hand, by-products are generally rich in various nutrients and functional compounds, e.g., dietary fibres and/or bioactive components such as flavonoids and polyphenols recognized as antimicrobial and anti-radical compounds. A possible strategy for their valorization is their use as feedstock for microbial fermentation by selected strains of yeast and lactic acid bacteria (LAB) for the production of valuable bio-based compounds. In particular, in this study olive pomace (OP) and tomato residues and seeds (TR) were analyzed, and 31 strains of yeasts were isolated from OP and 30 from TR. In addition, more than 50 strains of LAB were isolated from TR. Yeasts were characterized for some metabolic features such as lipase, protease and beta-glucosidase activities. When grown in culture media with OP or TR as the only nutrient source, marked lipolytic and proteolytic activities were shown by some yeast strains already after 2 days of incubation at 30°C. Moreover, more than 60 volatile compounds interesting for the food, cosmetics or chemical sectors were detected by GC/MS-SPME analysis. In particular, several molecules used as food flavouring or perfume compounds were identified. In conclusion, the results obtained indicate that the tested biotechnological approach can be a promising strategy for the exploitation of polluting by-products through the production of bio based flavours. From a technological point of view, the yeast isolates could be also exploited for bioremediation of olive oil wastewaters or as a source of enzymes of biotechnological interest.