Selection and optimization of a salting‐out extraction system for recovery of biobutanol from fermentation broth

Abstract

High separation cost of biobutanol from the fermentation broth has become a bottleneck in acetone‐butanol‐ethanol (ABE) industrial production due to low ABE concentration. In this study, a suitable salting‐out extraction (SOE) system was selected and optimized for the recovery of biobutanol from the fermentation broth. From the different SOE systems investigated, the acetone/K2HPO4 system appeared to be more favorable. To examine the potential of this SOE system, the partition coefficient combined with concentration fold of butanol in synthetic solutions was optimized by the response surface methodology. The optimum conditions were found to be 17.51% w/w acetone, 21.44% w/w dipotassium hydrogen phosphate at ABE concentration of 17.3 g/L (butanol = 9.5 g/L). Under these conditions, a favorable partition coefficient, extraction yield, and concentration fold of butanol were determined as 70, 99.08%, and 1.48, respectively. The optimum extraction conditions were then used to direct the recovery of biobutanol from a real fermentation broth. The partition coefficient, extraction yield, and concentration fold of butanol reached 63.13, 98.10%, and 1.53, respectively; while the removal ratio of cells and proteins were 99.12 and 95.70%, respectively. The SOE system of acetone/K2HPO4 appeared to be effective and feasible for the downstream processing of butanol from fermentation broth.