Microbial Consortia-Dependent Evolution of Physicochemical, Compositional and Functional Properties in Kombucha Fermentation

In recent decades, kombucha, a beverage produced through the fermentation of tea leaves by a symbiotic culture of bacteria and yeasts (SCOBY), has gained considerable popularity and attracted increasing scientific interest. However, the influence of SCOBY composition on kombucha characteristics remains insufficiently explored. In the present study, green tea kombuchas fermented with four different SCOBYs (SCs) were monitored over 21 days through physicochemical (pH), biochemical (total soluble solids (TSS), ethanol, proteins, and phenolic compounds), and microbiological (yeasts, acetic acid bacteria, and lactic acid bacteria) analyses. Based on these parameters, the most suitable bottling time was established for each kombucha (7 days for SC3 and SC4; 10 days for SC1 and SC2), considering acceptable and safe pH values, reduced TSS levels (4.3–4.6 °Brix), ethanol concentrations below 1.2%, and increased protein and phenolic compound contents, all of them differently affected by the SC used. At the selected bottling stages, the kombuchas exhibited DPPH● and ABTS●+ radical scavenging capacities (TEAC values up to 7.7 and 36.7 µmol/mL, respectively) and inhibitory activity against an Escherichia coli strain. These preliminary findings suggest the impact of SC composition and support further studies involving advanced phenolic, microbiological, and functional characterization approaches.