Bacterial cellulose from kombucha: Assessing inoculum age and concentration, and its conversion via enzymatic hydrolysis into cellobiose and glucose

Kombucha-type fermentation yields significant amounts of bacterial cellulose alongside the fermented beverage. This study evaluated the effects of inoculum age and concentration in kombucha-type fermentation using green acerola residue as an extract. The findings revealed that lower inoculum concentrations (2.5 and 5%) resulted in decreased bacterial cellulose (BC) yield. Conversely, increasing the inoculum concentration to 7.5% and 10% led to a 3.2-fold increase in BC yield. Inoculums aged just 3 days exhibited the lowest BC production, followed by older inoculums (9 and 12 days), suggesting reduced metabolic activity in the latter case. The optimal combination was found to be an inoculum age of 6 days and a concentration of 7.5%, resulting in a BC yield of up to 2.2 g/L using 70 g/L of carbon source. BC obtained from fermentation underwent enzymatic hydrolysis to yield cellobiose. Multi-stage hydrolysis - 1 stage (48 h), 2 (24 h, 24 h), 3 (12 h, 24 h, 24 h), and 4 (6 h, 6 h, 12 h, 24 h) - utilizing a methodology that anticipates the adsorption of endoglucanases onto the BC itself was employed to mitigate the inhibition of cellobiose on endoglucanases. The stages demonstrated an increase in cellobiose yield corresponding to the greater number of cycles, with 4 stages yielding 12.4% compared to 8.6% for hydrolysis conducted in a single stage. Despite the observed increase, the yield can be considered low and attributed to the loss of adsorbed enzymes between cycles due to the high crystallinity of the BC.