Production of Antimicrobial and Antioxidant Metabolites by Penicillium crustosum Using Lemon Peel as a Co-Substrate in Submerged Fermentation

TL;DR

This study shows that adding lemon peel to fungal fermentation boosts the production of natural antimicrobial and antioxidant compounds.

Contribution

The novel use of lemon peel as a co-substrate enhances bioactive metabolite production by Penicillium crustosum.

Findings

Semi-purified extracts showed MIC values of 185 µg/mL against P. aeruginosa and 225 µg/mL against MRSA.

Extracts exhibited strong ABTS radical-scavenging capacity (238.95 ± 2.17 µmol TE).

RP-HPLC-ESI-MS identified phenolic acids, flavanones, flavonols, and lignans in the extracts.

Abstract

Fungal secondary metabolites are valuable sources of natural antioxidants and antimicrobials. This study evaluated the submerged fermentation of Penicillium crustosum OR889307 supplemented with lemon peel as a co-substrate to enhance the production of bioactive compounds. Lemon peel was selected for its phenolic precursors and sustainable availability as an agro-industrial byproduct. Crude extracts, aqueous and organic fractions, and molecular-weight partitions were assessed for antioxidant activity using the DPPH assay and for antimicrobial activity against Escherichia coli, Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Pseudomonas aeruginosa, and Candida albicans. Semi-purified extracts from co-substrate fermentations exhibited enhanced bioactivity, showing MIC values of 185 µg/mL against P. aeruginosa and 225 µg/mL against MRSA, along with strong ABTS radical-scavenging capacity (238.95 ± 2.17 µmol TE). RP-HPLC-ESI-MS profiling revealed phenolic acids, flavanones, flavonols, and lignans, including ferulic acid 4-O-glucoside, bisdemethoxycurcumin, secoisolariciresinol, and quercetin 3-O-xylosyl-glucuronide. These findings demonstrate that lemon peel supplementation promotes the biosynthesis of antimicrobial and antioxidant metabolites by P. crustosum. This approach supports sustainable agro-waste valorization and offers a promising strategy for obtaining natural bioactive compounds with potential applications in food preservation and health-related formulations.

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