Bioconversion of Food and Green Waste into Valuable Compounds Using Solid-State Fermentation in Nonsterile Conditions

Agro-industrial residues have transitions from being an environmental problem to being a cost-effective source of biopolymers and value-added chemicals. However, the efficient extraction of the desired products from these residues requires pretreatments. Fungal biorefinery is a fascinating approach for the biotransformation of raw materials into multiple products in a single batch. In this study, the ability of Trichoderma asperellum R to convert fruit scrap and green waste into value-added chemicals was tested in solid-state and in nonsterile conditions. A solid-state fermentation protocol for a tray bioreactor was developed using spawn as the inoculum for nonsterile substrates. T. asperellum R drove the fermentation of both substrates, shaping the metabolites that were enriched in the secondary plant metabolites. Strain R showed cellulase activity only when inoculated on fruit scraps, resulting in increased amounts of polysaccharides in the crude extract. This extract was also enriched in vanillic acid and limonoid, which are intriguing compounds due to the increasing interest in their potential as biological nitrification inhibitors or food additives. Finally, trimethoxybenzaldehyde, an interesting chemical building block, was identified in the extracts of the Trichoderma-guided fermentation. The overall results showed that the application of T. asperellum R has potential as a driver to facilitate the extraction of bioactive substances from nonsterile recalcitrant substrates.