Development of Low-Caffeine Kombucha Using Lotus Root Tea and an Evaluation of Its Functional Properties

Kombucha, traditionally fermented from black or green tea, is well known for its potential health benefits. However, its high caffeine content may limit consumption for certain individuals. Therefore, this study aimed to develop a low-caffeine kombucha using lotus root tea as an alternative to black or green tea. Lotus root was roasted and brewed to prepare the tea base, to which sugar and a SCOBY were added for primary fermentation. Subsequently, Lactobacillus plantarum (1.0 × 10⁹ and 3.0 × 10⁹ CFU/mL) was inoculated to carry out secondary fermentation. The kombucha samples were assessed for their organic acid composition, antioxidant activity, antimicrobial effects, β-glucuronidase inhibition, and protective effects against Salmonella infection in a Caenorhabditis elegans model. The caffeine concentration of lotus root tea kombucha was significantly lower than that of conventional kombucha. L. plantarum fermentation increased the lactic acid concentration and enhanced antimicrobial activity, particularly against Escherichia coli OP50 and Salmonella typhimurium. Additionally, β-glucuronidase inhibition significantly improved, suggesting potential gut health benefits. In C. elegans, kombucha consumption improved survival rates following Salmonella infection, indicating a protective effect. This study demonstrates that fermentation using Lactobacillus plantarum can enhance the bioactivity of lotus root kombucha, highlighting its potential as a low-caffeine functional beverage.