“In situ” removal of isopropanol, butanol and ethanol from fermentation broth by gas stripping

• Gas stripping of isopropanol, butanol and ethanol (IBE) from model solutions was characterized.
• Solvent removal during C. beijerinckii cultivation enhances IBE productivity.
• New repeated batch process with discontinuous solvent removal at 70 °C has been demonstrated.

In this study, the removal of IBE from aqueous solutions by gas stripping has been characterized. The effect of one or more components in the solution on the kinetics of the separation has been studied, both at 37 °C and at 70 °C. Gas stripping has been applied to batch, repeated batch and continuous cultures of Clostridium beijerinckii grown on a glucose/xylose mixed sugar substrate mimicking lignocellulosic hydrolysates, with the aim of finding optimal conditions for a stable IBE-producing culture with high productivity. An innovative repeated-batch process has been demonstrated in which the gas-stripping is performed at 70 °C, resulting in a prolonged stable IBE culture.