Fruit peels as solid waste feedstock for astaxanthin production using Xanthophyllomyces dendrorhous fermentation

Astaxanthin is a high-value carotenoid with strong antioxidant activity and broad industrial applications. Using fruit peel extracts for astaxanthin production provides a sustainable pathway for the valorization of agricultural waste. This study investigated tangerine, pomegranate, and banana peel extracts as low-cost substrates for astaxanthin biosynthesis by Xanthophyllomyces dendrorhous. The peels were pretreated using three different pretreatment methods-mild heating at 45 °C, boiling, or acid hydrolysis-followed by fermentation to evaluate the effects of peel concentration and light exposure. Fruit peel extract media outperformed the conventional YM medium, with heating and boiling pretreatments showing higher efficiency than acid hydrolysis. Mild heating at 45 °C achieved superior performance without harsh chemicals, highlighting its eco-friendly and cost-effective potential. Light exposure enhanced astaxanthin biosynthesis, whereas higher biomass formation was observed under dark conditions. This work demonstrates that a mild, low-energy pretreatment combined with fruit peel valorization, particularly tangerine peel, is a promising strategy for sustainable astaxanthin production.