Anaerobic Bioconversion of Mixed Fruit Waste into Organic Acids and a Multifunctional Enzymatic Bioproduct in a...

The microbial valorization of agro-industrial residues is a promising strategy for sustainable bioprocesses and the development of a circular bioeconomy. In this study, mixed fruit peel waste was anaerobically fermented in a stirred-tank bioreactor using Wickerhamomyces sp. UFFS-CE-3.1.2 to produce organic acids and a multifunctional enzymatic bioproduct. During fermentation, sugars decreased from 6.51 to 0.22 g L^-1, leading to the formation of citric acid (7.65 g L^-1), ethanol (3.77 g L^-1), glycerol (0.53 g L^-1), and acetic acid (0.37 g L^-1). The accumulation of organic acids likely imposed metabolic stress on the yeast, triggering physiological responses that mitigate oxidative stress. Consequently, the resulting enzymatic extract exhibited high lipase activity (185.63 U mL^-1), late catalase induction (520.97 U mL^-1), and stable superoxide dismutase activity (50 U mL^-1). This enzymatic profile indicates the formation of a stress-adapted microbial system with potential applicability in processes involving lipid hydrolysis and oxidative mechanisms. The process was conducted without supplementation of synthetic medium and operated stably in a stirred-tank bioreactor. Overall, these results suggest a feasible microbial strategy for converting fruit waste into value-added bioproducts, contributing to the development of sustainable biotechnological processes.