Kombucha-Derived Bacterial Cellulose for Active and Biodegradable Food Packaging: Production, Modification, Performance, and Current Challenges.

Kombucha fermentation generates two fractions of potential relevance to food-packaging applications: a fermented liquid containing organic acids, polyphenols and other metabolites, and a cellulose-rich pellicle formed by cellulose-producing acetic acid bacteria. However, the fermented beverage, raw pellicle and purified kombucha-derived bacterial cellulose (KBC) differ substantially in composition, functionality and food-contact suitability and should not be treated as interchangeable materials. This review critically examines bacterial cellulose formation during kombucha fermentation, purification and modification strategies, packaging-relevant properties, and the application of kombucha-derived materials in films, coatings and composites. Purified KBC provides a continuous nanofibrillar network and can exhibit good mechanical and oxygen-barrier properties under dry conditions. Its hydrophilic character, however, promotes moisture sorption and swelling, which may impair mechanical integrity and barrier performance at elevated relative humidity. Blending, coating, grafting and crosslinking can improve selected material properties, but their effects are formulation-specific and may involve trade-offs between moisture resistance, mechanical performance, biodegradability and food-contact safety. Fermented kombucha liquid and native or mildly washed pellicles may contribute fermentation-derived bioactive compounds; however, antioxidant or antimicrobial activity measured in the beverage or raw pellicle cannot be automatically attributed to purified KBC or the final packaging material. Current evidence supports the use of KBC as a structural matrix, reinforcing phase, coating component or carrier of active substances. Nevertheless, limited migration data, heterogeneous testing conditions, insufficient real-food studies and a lack of pilot-scale, regulatory and life-cycle assessments currently restrict its broader industrial implementation.