Production of Phenolic and Antioxidant Compounds by Fungi through Solid-state Fermentation on Banana Peel

Background: Solid-state fermentation (SSF) has emerged as an effective bioprocess for converting agro-industrial residues into high-value bioactive compounds. In this study, the production of total phenolic compounds and antioxidant-related enzymes by Basidiomycete and Ascomycete fungi was evaluated using banana peel, an abundant food-waste substrate. Four Basidiomycete and four Ascomycete species were assessed and compared on banana peel and potato dextrose agar media. Methods: Fungal cultures were subjected to SSF followed by quantification of enzymatic and antioxidant parameters, including laccase activity (ABTS assay [2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid)], catalase activity [CAT] [titanium dioxide, TiO₂ reagent method], total phenolic content (Folin–Ciocalteu assay), reducing power assay, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity. Statistical comparisons were performed using the one-way analysis of variance. Results: Basidiomycota species demonstrated markedly higher laccase activity than Ascomycota species across both media. Clitopilus prunulus BV18 exhibited the highest laccase activity (900.63 U/mL). Conversely, Ascomycota species produced greater CAT, with Xylaria polymorpha BV5 achieving the highest level (6.76 µmol H₂O₂/mL). Phenolic compound biosynthesis varied significantly among species; Basidiomycetes exhibited overall superiority, particularly on banana peel medium, where Pleurotus pulmonarius BV13 and C. prunulus BV18 produced the highest total phenolic contents (388.67 and 287.33 µg/mL, respectively). DPPH radical scavenging activity was also highest in P. pulmonarius BV13, C. prunulus BV18, and X. polymorpha BV5 on banana peel substrate. Conclusions: Basidiomycota fungi exhibit strong inherent potential for the biotransformation of food waste into phenolic-rich antioxidant metabolites under SSF conditions. Their markedly higher phenolic production and antioxidant activity, compared with Ascomycetes, highlight their suitability for sustainable bioprocessing applications aimed at valorizing agro-industrial waste streams.