Fermentation impact: A comparative study on the functional and biological properties of Banana peel waste

Banana fruit is a highly consumed and widely cultivated world food crop that generates plenty of waste globally. In this work, the phytochemical, nutritional, scavenging and therapeutic potentials of banana peel (BP) extracts were compared before and after fermentation. Halophilic fungi (<i>Alternaria alternata</i>, <i>Pleosporaceae</i> spp., <i>Fusarium culmorum</i>) were used in fermentation media designated as fermented banana peel FBP1, FBP2, and FBP3, respectively. Phytochemical coumarins, terpenoids, tannins, saponins, quinones, flavonoids, alkaloids, carbohydrates, proteins and steroids were found in all extracts while anthraquinone was identified in BP extracts only. Fermented extracts showed less quantity of Carbohydrate, compared to BP (477.1 ± 28.93 mg/g). Fermentation influenced the protein concentration as FBP1 showed a maximum protein of 56.9 ± 8.91 mg/g. Decreased quantities of Total Phenolic Contents (TPC), Total Flavonoid contents (TFC), and Vitamin C were noted in fermented products. The BP contained TPC (18 ± 2.59 mg GAE/g), TFC (20.5 ± 2.11 mg QE/g), carotenoid (1.03 ± 0.19 mg/g) and vitamin C (33.46 ± 2.63 mg/L). For BP, high antioxidant activity was observed, IC₅₀ values of DPPH scavenging and FRAP assay were 2.01 ± 0.06 mg/mL and 12.81 ± 0.03 mg/mL, respectively. All the extracts were potentially active against the <i>Salmonella typhi, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus</i> and <i>Escherichia coli</i> BP extract showed high antibacterial activity than the fermented products. Among all the above, <i>S. aureus</i> showed high sensitivity to BP and FBP2 with 26.33 ± 2.49 and 26.33 ± 0.97 mm zone of inhibition and <i>S. typhi</i> was highly inhibited by BP and FBP1 with 26.26 ± 1.77 and 26.66 ± 2.63 mm. BP was highly active against <i>K. pneumoniae</i> and <i>P. aeruginosa</i> with 31.33 ± 1.74 and 32.33 ± 1.59 mm zone of inhibition and <i>E. coli</i> was sensitive to FBP2 with 25.7 ± 2.33 mm zone, respectively. The BP extract possessed potent antifungal activity against <i>Mucor mucedo</i> (84 %), <i>Aspergillus niger</i> (72 %) and <i>Aspergillus flavus</i> (83 %), which was higher than the fermented products. The antileishmanial assay was undertaken for all extracts against promastigotes of <i>Leishmania major</i>, BP showed good activity IC₅₀ = 0.763 ± 0.01 mg/g. In the anti-inflammatory assays the BP showed lowest IC₅₀ values by protein denaturing (0.612 ± 0.01), proteinase inhibitory (0.502 ± 0.01) and blood hemolysis assay (0.515 ± 0.01 mg/g). The minimum concentration indicated that BP was highly potent in response to antileishmanial and inflammation activity.