Using poly(vinyldodecylimidazolium bromide) for the in‐situ product recovery of n‐butanol

Abstract

The mitigation of end‐product inhibition during the biosynthesis of n‐butanol is demonstrated for an in‐situ product recovery (ISPR) system employing a poly(ionic liquid) (PIL) absorbent. The thermodynamic affinity of poly(vinyldodecylimidazolium bromide) [P(VC12ImBr)] for n‐butanol, acetone and ethanol versus water was measured at conditions experienced in a typical acetone‐ethanol‐butanol (ABE) fermentation. In addition to providing a high n‐butanol partition coefficient (PC = 6.5) and selectivity (αBuOH/water = 46), P(VC12ImBr) is shown to be biocompatible with Saccharomyces cerevisiae and Clostridium acetobutylicum. Furthermore, the diffusivity of n‐butanol in a hydrated PIL provides absorption rates that support ISPR applications. Using a 5 wt% PIL phase fraction relative to the aqueous phase mass, P(VC12ImBr) improved the volumetric productivity of a batch ABE ISPR process by 31% relative to a control fermentation. The concentration of n‐butanol in the P(VC12ImBr) phase was sufficient to increase the alcohol concentration from 1.5 wt% in the fermentation medium to 25 wt% in the saturated PIL, thereby facilitating downstream n‐butanol recovery.