RESUMO
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(VC12 ImBr)] 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(VC12 ImBr) 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(VC12 ImBr) 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(VC12 ImBr) 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.