Biochemical Content, Antimicrobial, and Larvicidal Activities of Jiaosu Derived from Different Combinations of Fruit Wastes

Valorization of fruit wastes through fermentation yields a multipurpose liquid called jiaosu. This study was conducted to compare the biochemical content changes (pH, total proteins, total carbohydrates, total phenolics, total alcohols, and organic acids) before and after fermentation for three months, as well as to evaluate the antibacterial, antifungal, and mosquito larvicidal activities of three combinations of jiaosu samples, orange-papaya-watermelon (OPW), grapefruit-mango-pineapple (GMP), and durian-jackfruit-passion fruit (DJP). After fermentation, the jiaosu samples were acidic (pH 3.05-3.40). Only GMP and DJP showed increased total protein content (p < 0.05). All samples utilized carbohydrates extensively during fermentation and displayed significant increases (p < 0.05) in total phenolic contents. Alcohols were detected in all samples (2.15% +/- 0.05%-8.34% +/- 0.06%) after fermentation. All organic acids (oxalic, tartaric, malic, lactic, acetic, citric, and succinic acids) were significantly increased (p < 0.05) in all samples except for the tartaric and succinic acids in OPW which decreased after fermentation. All samples exhibited minimum inhibitory concentrations of 25-50% v/v against five species of human pathogenic bacteria and minimum fungicidal concentrations of 12.5-50% v/v against the fungus Cryptococcus neoformans. All samples showed strong larvicidal activity against the third instar larvae of Aedes spp. mosquitoes. The larvae of Aedes aegypti were more susceptible to the jiaosu samples than Aedes albopictus with the respective median lethal concentrations (LC50) of 2.14-5.16% v/v and 6.52-14.55% v/v, after 24 h post-treatment. The findings from this study recorded the biochemical changes in different fruit peel combinations of jiaosu during fermentation and the potential use of jiaosu as cleaning agent and biopesticide.