Kombucha as a Bioactive Functional Beverage: Current Evidence, Production Challenges, and Future Perspectives

Kombucha is a beverage obtained through the fermentation of tea leaves by a symbiotic culture of bacteria and yeast called SCOBY. This beverage is popularly known for the potential health benefits associated with its consumption, which is the main reason for its commercial expansion over the last century. These potential benefits are linked to the presence of a wide variety of bioactive compounds, notably phenolic compounds and organic acids. This composition varies significantly depending on the fermentation conditions, which in turn modifies the beverage's bioactive properties (i.e., antioxidant capacity or antimicrobial properties, among others). For this reason, the most recent advances in kombucha production are geared towards achieving standardized production, including strategies for enhancing bioactive content and fortification with functional ingredients. All these advances should satisfy quality control and regulatory compliance. However, despite the growing scientific and commercial interest in kombucha, current knowledge remains fragmented across different disciplines, highlighting the need for an updated and integrative overview of its composition, bioactivity, production variables, and safety aspects. In this review, nutritional, microbiological, and technological perspectives are integrated to provide an updated framework for understanding kombucha as a functional beverage, while also outlining key directions for future research and industrial application.