Unveiling Valuable Secondary Metabolites from the Bioconversion of Banana ( <i>Musa balbisiana</i> ) Peel-Derived Biomass with <i>Aspergillus niger</i> . Metabolomic Insights into the Chemical Profiles

Santa Catarina is Brazil's fourth-largest banana producer, generating a significant amount of waste. Banana peel conversion into useful products is uncommon. However, it produces natural products that possess benefits for human health or can serve as biomass to produce fungi-derived metabolites. Therefore, <i>Aspergillus niger</i> was isolated from banana peels and then cultured on three distinct media composed of starch, banana peels (BP), and starch-enriched banana peels (BPS) for 14, 21, and 28 days at 28 °C. Their chemical profiles were established using liquid chromatography coupled to mass spectrometry data assisted by the GNPS database and MS-FINDER software. In BP media, 76 secondary metabolites were detected; among them, 66 were produced by the fungus. Twenty-seven compounds, such as nigragillin and pyranonigrin A, are <i>A. niger</i> chemomarkers, while other substances, except for the 13 unidentified, were previously found in other organisms. Among the 99 metabolites detected in BPS media, 22 were previously identified as <i>A. niger</i>-derived compounds. BPS media also yielded 26 unidentified compounds, while 12 annotated ones were also found in BP. The remaining metabolites were previously reported in other organisms. Principal component 1 of 44.8% and principal component 2 of 22.2% indicated that 21-day fermentation for BP medium and 28-day fermentation for BPS medium were the optimal conditions to produce secondary metabolites. Variable importance plots reveal nonadecan-2-amine (score >3) and an alkylaryl amine derivative (<i>m</i>/<i>z</i> 304.3005) as the most concentrated compounds. The present results showed a cheap process to turn food residues and waste into valuable molecules.