Levulinic acid as a strategy for control of postharvest citrus blue mold by a newly isolated Penicillium italicum

BACKGROUND; Levulinic acid (LA) is a multifunctional compound that is relevant to the economy of bio-based chemical products. Citrus sinensis, the Valencia variety, is one of the world's most consumed citrus fruit varieties but suffers significant losses as a result of blue mold infestation. This research evaluated the inhibitory action of unpurified levulinic acid obtained from watermelon residues against the fungus Penicillium italicum, proposing a new use as a fungal inhibitor. RESULTS: LA was evaluated in in vitro tests and inhibited the mycelial growth of the fungus. In in vivo experiments with oranges, fungal proliferation in fruits was investigated by applying a crude mixture containing LA (43 mmol L-1) and formic acid (FA, 28 mmol L-1), and comparing the effects with FA alone and negative control (without inhibitory agent). The weight loss and disease incidence results decreased when LA was used as an inhibitory agent, with no negative impacts on fruit quality being observed. Its inhibitory effect was confirmed by determining the activities of the antioxidant enzymes catalase (CAT), ascorbate peroxidase (APX), superoxide dismutase (SOD) and peroxidase (POD), where there was no increase in activities owing to inhibition of the fungus before its proliferation in the fruits. CONCLUSION: This study provides relevant data on the new use of raw LA as an antifungal agent, an effect still unexplored for this compound in recent literature, offering a practical and innovative solution to combat blue mold. (c) 2024 Society of Chemical Industry (SCI).