Bioactive compounds in kombucha: A review of substrate effect and fermentation conditions

•Content of bioactive compounds vary depending on the raw materials used in kombucha.•Type of sugar used for kombucha fermentation influence levels of bioactive compounds.•The optimization of process conditions can improve bioactive profile of kombucha.•Content of substances with beneficial effects are most often enhanced in Kombucha. Plant bioactive compounds have been studied mainly for their beneficial antioxidant properties. Kombucha is a fermented beverage traditionally obtained from fermentation of sweetened black or green tea by a characteristic consortium of yeasts and bacteria. The beverage naturally contains bioactive compounds from teas and their synthesis can be increased during fermentation. This review aims to explore the different bioactive compounds found in kombucha from different substrates, as well as the factors that influence on their synthesis and their amount in the final product. The results suggest phenolic compounds are the main bioactive compounds in kombucha. The substrate type contributes the most to increasing the content of bioactive compounds in the final product; fermentation time and type of sugar also increase the amount of these compounds. Further research suggestions include the combination of strategies to increase bioactive compounds in kombucha, quantification and characterization of the isolated compounds.