How do different sucrose concentrations affect the dry mass of bacterial cellulose (SCOBY biofilm) in de novo kombucha fermentation in black tea over 10 days?

Kombucha, a fermented tea produced by a symbiotic culture of bacteria and yeast (SCOBY), generates bacterial cellulose, a high-purity biopolymer with valuable applications in sustainable material science, including textiles, packaging, and biomedical materials. During fermentation, this cellulose forms a pellicle, a gelatinous biofilm at the liquid surface that serves as a visible and protective layer over the culture. Despite its increasing relevance in both artisanal and industrial contexts, the optimal conditions for de novo pellicle formation, particularly in the absence of a pre-existing SCOBY, remain poorly defined. We hypothesised that higher sucrose concentrations in black tea kombucha would positively influence the dry mass of bacterial cellulose produced by the pellicle during ten days of de novo fermentation, because sugar monomers are the building blocks for bacterial cellulose production. To test this hypothesis, black tea was inoculated with 10% raw starter culture and fermented at six sucrose concentrations (0%, 4%, 8%, 12%, 16%, and 20% w/v) in triplicate for 10 days at 22 ± 2°C. SCOBY dry mass increased in a dose-dependent manner up to 16% w/v, after which no further gains were observed. No pellicle formed in the 0% control, confirming that sucrose is an essential carbon source and that carryover from the starter culture did not support SCOBY growth. The most consistent and robust pellicles formed at 16% w/v, while lower sugar levels produced fragile biofilms. These results indicate that 16% sucrose provides optimal conditions for bacterial cellulose production in de novo kombucha fermentation for 10 days. This finding not only offers practical guidance for home brewers but also supports the scalable production of bacterial cellulose for use in advanced materials, highlighting its potential as a sustainable alternative to traditional plant-based polymers.