Enhanced Acetone-butanol Production from Sugarcane Juice by Immobilized Clostridium acetobutylicum (ATCC 824) on thin-shell silk cocoons

To promote its performance during acetone-butanol-ethanol (ABE) fermentation, Clostridium acetobutylicum (ATCC 824) was immobilized on a thin-shell silk cocoon (TSC). As a residual from the silk industry, TSC offers a cheap, biocompatible support material. The adsorbed C. acetobutylicum cells digested the TSCs into amino acids as a nitrogen source. It was shown that TSC might promote the phase shift to acetone in the ABE fermentation. At an initial reducing sugar concentration of 90 g/L, the ABE productivity of the immobilized cell culture on TSC (IC-TSC) in batch fermentation was 0.18 g/L/h, and the solvent mixture comprised 6.1 g/L acetone, 15.9 g/L butanol, and 1.9 g/L ethanol. Repeated 4-cycle batch fermentation using IC-TSC significantly improved the ABE productivity. After 48 h of cyclic fermentation, the maximum ABE productivity was 0.43 g/L/h with acetone, butanol and ethanol concentrations of 6.6, 12.9, and 1.1 g/L, respectively.