Milk Whey Fermented by Kombucha SCOBY: Effect of Sugar on the Physicochemical and Microbiological Properties of the New Beverage

Kombucha, a traditional drink crafted from fermented sweetened black or green tea using a symbiotic association of bacteria and yeasts known as SCOBY, has become a popular product in Western countries. Whey, a nutrient-rich byproduct of dairy production, provides an interesting option as substrate for producing novel beverages. Here, we aimed at evaluating the fermentation of whey, with (WS) or without (W) supplementation of sucrose, by using the SCOBY microbiota of kombucha. The variables pH, acidity, acetic acid and ethanol concentrations, and the microbial composition of the whey-based beverages were analyzed. W and WS were fermented during 7 days at 25 degrees C, without agitation to emulate kombucha fermentation conditions. Results show volatile acidity levels ranging from 342 to 1612% and 280 to 3358% of acetic acid equivalent per liter for WS and W, respectively. The initial pH of 6.0 decreased to 4.5 and 3.7 in WS and W fermented beverages, respectively. Under both fermentation conditions, final ethanol concentrations were higher than 0.5% in volume, classifying the product as alcoholic. Predominant taxa identified in SCOBY fermentation included the bacterial genus Komagataeibacter and the fungal genus Zygosaccharomyces in both media, with greater microbial abundance observed in WS. These results highlight the potential of this beverage as a functional product.