Effect of additives on bacterial cellulose yield and properties in Thai red tea Kombucha fermentation

This study evaluates the impact of selected additives-ethanol, vitamin C (VC), pure coffee (PC), yeast extract (YE), and soy protein isolate (SPI)-on bacterial cellulose (BC) production during kombucha fermentation using Thai red tea. Additive types and concentrations were chosen based on prior efficacy in BC production. Static fermentation at 30 °C for 15 days showed ethanol increased BC wet yield by 39.79 % (218.36 ± 12.85 g/L) and VC by 11.50 %, while pure coffee, yeast extract, and soy protein isolate reduced yield, with yeast extract yielding the lowest (61.73 ± 9.58 g/L). Structural analyses (SEM, FTIR, XRD) confirmed type I cellulose with high crystallinity (80-88 %) and typical nanofibrillar morphology across samples. Thermal stability (TGA) was similar among the studied treatments, with ethanol and VC enhancing residue formation and degradation temperature. Nano-indentation revealed that ethanol-derived BC had slightly lower stiffness (4.03 GPa) compared to VC-treated BC (4.47 GPa), reflecting differences in fiber assembly and crystallinity. Overall, the supplementation of ethanol or VC was found to enhance the yield of BC, while also modulating its physical and mechanical properties. These findings highlight the potential of such additives as effective strategies for optimizing BC production, with implications for both biological applications and industrial-scale utilization.