Adding value to vegetable waste: Oil press cakes as substrates for microbial decalactone production

Abstract

AbstractIn this study several oil press cakes were investigated as exclusive substrates for different moulds and yeasts for the production of flavor‐active decalactones via solid‐state fermentation (SSF). Experiments are focused on pre‐treatment methods for olive cake to remove antimicrobial phenolic substances contained in the oil cake disturbing or even inhibiting microbial growth. Choosing Ceratocystis moniliformis as the reference microorganism best results were obtained by a combination of hot water flushes and enzymatic treatment of the cake. Fermentation with sunflower, olive and linseed cake did not lead to lactone formation in detectable amounts although all of these substrates provided good microbial growth. On castor cake, however, five microorganisms have synthesized the requested decalactones via SSF. Thus fermentation of the fungus Moniliella suaveolens on this substrate resulted in a maximum concentration of γ‐decalactone of 180.7 mg·kg−1 dry matter without optimization. Another δ‐lactone, 6‐pentyl‐α‐pyrone, was produced in small amounts by the fungus Trichoderma harzianum on castor cake.