Controlled Fermentation and Integrated Valorization of Coffee Cherry Pulp: Applications in Food, Bioactive, Biopolymers, and Animal Feed

Coffee cherry pulp (CCP; cascara), a major by-product of coffee processing, has gained increasing attention as a sustainable source of phenolic compounds, dietary fiber, and other bioactive constituents with applications in food, nutraceutical, feed, and biomaterial industries. However, its utilization remains limited by compositional variability, anti-nutritional compounds, and inefficiencies in conventional processing. Controlled fermentation has emerged as a promising strategy to enhance the release, transformation, and bioavailability of CCP-derived bioactive through targeted microbial biotransformation and controlled bioprocessing. This review summarizes recent advances in enzymatic pretreatment, microbial fermentation, and metabolite-directed processing, with emphasis on their effects on phenolic transformation, antioxidant activity, and functional properties. The roles of selected lactic acid bacteria, yeasts, and microbial consortia in improving the nutritional, sensory, and biological characteristics of CCP-derived products are critically discussed. Potential applications of fermented CCP in functional foods and beverages, bioactive ingredients, biopolymers, and animal feed are also highlighted within the framework of an integrated circular bioeconomy. Finally, current challenges and future perspectives related to process scalability, metabolite control, regulatory approval, and AI-assisted bioprocess optimization are addressed.