Fruit and vegetables are among the food groups with the highest post-harvest losses, with an estimated 40% of production discarded worldwide. This organic waste significantly contributes to greenhouse gas emissions, particularly methane, during decomposition, emphasising the need for sustainable and circular strategies to valorise resources. This study aimed to develop a sustainable method for producing antimicrobial peptides (AMPs) from fruit peel waste using genetically modified Saccharomyces cerevisiae expressing the Ethanol Red TDH1 (ER TDH1) gene and to evaluate their potential against microbial pathogens.

Waste peels of mango, pineapple, banana, and apple were processed into must. The musts underwent acid hydrolysis, followed by alcoholic fermentation with S. cerevisiae ER TDH1. After fermentation, peptides <10 kDa were extracted from the cell-free supernatant by ultrafiltration and tested against microbial pathogens, including E. coli, P. aeruginosa, S. aureus, and C. albicans. Glucose, fructose, and ethanol levels were monitored throughout. For peptide production comparison, alcoholic fermentation of a synthetic must was performed, yielding higher ethanol (14 g/L) than fermentation of fruit must (3 g/L). The <10 kDa peptide fraction from fruit must showed strong inhibition of S. aureus and C. albicans (MIC = 1.47 mg/mL), while synthetic must peptides performed better against E. coli and P. aeruginosa (MIC = 1.47 mg/mL). AMPs derived from fruit waste via fermentation show promising antimicrobial activity, particularly against Gram-positive bacteria and yeast, highlighting their potential as sustainable, natural antimicrobial agents for pharmaceutical or food product applications, while contributing to circular economy principles by transforming underutilized biomass into high-value bioactive compounds.