CONTINUOUS PRODUCTION OF ISOVALERALDEHYDE THROUGH EXTRACTIVE BIOCONVERSION IN A HOLLOW-FIBER MEMBRANE BIOREACTOR

A membrane bioreactor was developed to perform an extractive bioconver sion aimed at the production of isovaleraldehyde by isoamyl alcohol ox idation with whole cells of Gluconobacter oxydans. A liquid/liquid ext ractive system using isooctane as extractant and assisted by a hollow- fiber hydrophobic membrane was chosen to recover the product. The aque ous bioconversion phase and the organic phase were maintained apart wi th the aid of the membrane. The extraction of alcohol and aldehyde was evaluated by performing equilibrium and mass transfer kinetic studies . The bioprocess was then performed in a continuous mode with addition of the substrate to the aqueous phase. Fresh solvent was added to the organic phase and exhausted solvent was removed at the same flow rate . The extractive system enabled a fast and selective in situ removal o f the aldehyde from the water to the organic phase. High conversions ( 72-90%) and overall productivity (2.0-3.0 g l(-1) h(-1)) were obtained in continuous experiments performed with different rates of alcohol a ddition (1.5-3.5 g l(-1) h(-1)). Cell deactivation was observed after 10-12 h of operation. (C) 1997 by Elsevier Science Inc.