Solvent productivity improvement in acetone-butanol fermentation by two-stage continuous system

Abstract

Two-stage continuous system was applied to improve solvent productivity in acetone-butanol fermentation of Clostridium acetobutylicum ATCC 824. In this system, the medium concentration, pH, and temperature were kept constant at 50 g/l glucose, 4.8, and 35ํC, respectively. The optimum dilution rates of 0.17 hr-1 in the first stage and 0.057 hr-1 in the second stage were obtained from the experiment. The maximum solvent productivity was 0.63 g/l-hr, which was 42% of that obtained from the single-stage continuous system, while the solvent concentration was increased by 1.7 times, which was more suitable for separation. By coupling this system with microfiltration in the second stage, the solvent productivity was increased to 3.7 times that of the single-stage continuous system, or 8.9 times that of the two-stage continuous system without microfiltration. The optimum dilution rates for the first stage and the second stage were 0.17 hr-1 and 0.55 hr-1, respectively, and the solvent concentration was close to that of the two-stage continuous system without microfiltration. Then the most suitable system which was applied to improve solvent productivity, was the two-stage system coupling with microfiltration.