Enhanced acetone‐butanol fermentation using repeated fed‐batch operation coupled with cell recycle by membrane and simultaneous removal of inhibitory products by adsorption

Abstract

A novel acetone–butanol production process was developed which integrates a repeated fed‐batch fermentation with continuous product removal and cell recycle. The inhibitory product concentrations of the fermentation by Clostridium acetobutylicum were reduced by the simultaneous extraction process using polyvinylpyridine (PVP) as an adsorbent. Because of the reduced inhibition effect, a higher specific cell growth rate and thus a higher product formation rate was achieved. The cell recycle using membrane separation increased the total cell mass density and, therefore, enhanced the reactor productivity. The repeated fed‐batchoperation overcame the drawbacks typically associated with a batch operation such as down times, long lag period, and the limitation on the maximum initial substrate concentration allowed due to the substrate inhibition. Unlike a continuous operation, the repeated fed‐batch operation could beoperated for a long time at a relatively higher substrate concentration without sacrificing the substrate loss in the effluent. As a result, the integrated process reached 47.2 g/L in the equivalent solvent concentration (including acetone, butanol, and ethanol) and 1.69 g/L · h in the fermentor productivity, on average, over a 239.5‐h period. Compared with a controlled traditional batch acetone–butanol fermentation, the equivalent solvent concentration and the tormentor productivity were increased by 140% and 320%, respectively. © 1995 John Wiley & Sons Inc.