Preliminary experiment of Saccharomyces cerevisiae immobilization using method of in situ flocculation

Ethanol is an important chemical in industrial application, i.e. solvent, disinfectant/antiseptic, intermediate chemical, and renewable energy. During the global pandemic, the price of ethanol increases significantly as the increasing demand. This research was a preliminary experiment to develop a method of cell immobilization of Saccharomyces cerevisiae using flocculation technique in situ in continuous fermentation implemented in an integrated aerobic-anaerobic baffled reactor (IAABR). Flocculant solution of polyacrylamide (15 g/L) was dosed gradually into the compartment B of the reactor by fraction of 2% v/v when the cell population of 1.03 x 10⁸ cells/mL. The cell would be entangled into the flocs inducing a decrease of free cell population in the medium phase. It reached a minimum population of 7.17 x 10⁶ cell/mL at 24 hours after flocculation when the sucrose medium of 2% w/v initiated to feed (500 mL/h) into the reactor. The feeding sucrose has already supported the yeast growth up to 2.32 x 10⁷ cells/mL after 18 hours. In this experiment, the flocculation in situ has been carried out successfully and needs to be analysed for ethanol fermentation performance. This preliminary experiment results in the highest ethanol concentration of 4.85%.