Utilization of Ziziphus jujuba Fruits in Kombucha Fermentation: Effects on Microbial Ecology and Polyphenol Transformation

This study focuses on the molecular characterization of Ziziphus jujuba fruits and their application in kombucha fermentation. Despite its traditional medicinal use, Z. jujuba remains poorly explored phytochemically. A preliminary multi-analytical investigation revealed the presence of bioactive molecules such as flavonoids, anthocyanins and tannins, along with high antioxidant capacity. Based on these results, we evaluated how the addition of Z. jujuba fruits affects the microbial ecology of the kombucha starter (Symbiotic Culture Of Bacteria and Yeast, SCOBY). Fermentations were conducted in black tea, with the addition of the dried fruits, for 11 days at 30 °C using the microbial consortium in the SCOBY consisting of Clavispora lusitaniae, Zygosaccharomyces bailii, Saccharomyces cerevisiae, and Komagataeibacter rhaeticus. In addition, since C. lusitaniae, Z. bailii, and S. cerevisiae were expected to enzymatically modify phenolic molecules, increasing their release, we determined whether the bioavailability of fruit polyphenols increases during fermentation; thus, increasing the bioavailability of polyphenols. Our results aim to define the potential of a kombucha beverage enriched with more readily bioavailable bioactive compounds.