Fermented kombucha tea: A dual source of bioactive compounds from tea and Symbiotic culture of Bacteria and Yeasts (SCOBY)

Kombucha is a fermented tea beverage recognized for its antioxidant, antimicrobial, and antifungal properties, offering potential health benefits [ 1 ]. This study investigates the preparation of kombucha using high-quality green tea. To prepare the tea, 5 g of tea leaves are added to 1 L of boiling tap water and infused at temperatures between 70 and 95°C for no more than 15 minutes. Organic, unrefined sugar serves as the fermentation substrate. The SCOBY, a consortium of bacteria and yeast, is sourced from Medica Laboratories in Romania and cultivated in a sugar-based medium containing a 3% (w/v) green tea infusion to promote the microbial activity necessary for fermentation. The fermentation process begins by adding the SCOBY and sugar to the cooled tea mixture. Primary fermentation occurs for 10-14 days at room temperature (22±2°C), with ultrasonication applied to break down plant cells and release nutrients, stimulating microbial activity. Aeration introduces sterile oxygen to enhance yeast growth, while artificial lighting influences the production of secondary metabolites. The kombucha is then transferred to airtight glass bottles for maturation over 1-2 weeks to achieve natural carbonation (secondary fermentation). Metabolic profiling using UHPLC-Q-Orbitrap-HRMS reveals bioactive metabolites. The kombucha demonstrates antioxidant activity (2.331-2.506 μM TE/mL) and significant antimicrobial and antifungal activity against E. coli, S. aureus, B. subtilis, and various fungal pathogens. These findings highlight the functional potential of SCOBY-based kombucha as a beverage with remarkable bioactive properties. Funding Project funded under the National Recovery and Resilience Plan (NRRP), Mission 4 Component 2 Investment 1.4 – Call for tender No. 3138 of December 16, 2021, rectified by Decree 374 n.3175 of December 18, 2021, from the Italian Ministry of University and Research and financed by the European Union – NextGenerationEU; Award Number: Project code CN_00000033, Concession Decree No. 1034 of June 17, 2022, adopted by the Italian Ministry of University and Research, CUP: D43C22001260001, Project title “National Biodiversity Future Center – NBFC. Publication History Article published online: 05 March 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany