Agro-industrial fruit peel powders as substrates for pigment production by Penicillium sp. UFPEDA 2569 and evaluation of antioxidant and antibacterial activities

Abstract The growing global demand for natural, safe, and sustainable colorants has intensified the search for microbial sources of bioactive pigments, driven by increasing awareness of the health and environmental risks associated with synthetic dyes. In this study, agro-industrial residues, represented by banana peel powder and passion fruit peel powder, were evaluated as alternative culture media substrates to support growth and pigment production by a Penicillium sp. UFPEDA 2569 strain. Fermentation was conducted under submerged conditions at 30 °C, pH 3.6, for 15 days. Pigments were extracted with dichloromethane and resuspended in 95% ethanol to yield the passion fruit ethanolic pigmented extract (PFEPE) and the banana ethanolic pigmented extract (BEPE). Both extracts were characterized by UV-Vis scanning and FT-IR spectroscopy and evaluated for antibacterial activity by broth microdilution and antioxidant activity using DPPH, ABTS and phosphomolybdenum assays. Spectroscopic profiles suggested the presence of putative carotenoid-like pigments, and PFEPE showed higher crude extract yield than BEPE (3.39 versus 0.68 g, respectively). The antibacterial activity against the six tested bacterial strains was weak, with MIC values ranging from 1,875 to 30,000 µg/mL. In contrast, both extracts showed antioxidant activity by the phosphomolybdenum method; BEPE was notably active (EC 50 = 408.88 µg/mL), surpassing the ascorbic acid positive control (EC 50 = 500.00 µg/mL). These results indicate that agro-industrial residues are viable substrates for fungal pigment production and highlight the antioxidant potential of the resulting pigmented extract, particularly BEPE.