Epoxidation of 1,7-octadiene by Pseudomonas oleovorans in a membrane bioreactor

A growing cell culture of Pseudomonas oleovorans was used to biotransform 1 ,7-octadiene to 1,2-epoxy-7,8-octene in a continuous-flow bioreactor with a n external membrane module. A dense silicone rubber membrane was used to co ntact an organic phase, containing both the reactant (1,7-octadiene) and th e growth substrate (heptane), with an aqueous biomedium phase containing th e biocatalyst. Heptane and octadiene delivery to the aqueous phase, and epo xide extraction into the solvent, occurred by diffusion across the dense me mbrane under a concentration-driving force. In addition, a liquid feed of h eptane and octadiene was pumped directly into the bioreactor to increase th e rate of delivery of these compounds to the aqueous phase. In this system 1,2-epoxy-7,8-octene accumulated in a pure solvent phase, thus, product rec overy problems associated with emulsion formation were avoided. Furthermore , no phase breakthrough of either liquid across the membrane was observed. In this system, the highest volumetric productivity obtained was 30 U.L-1, and this was achieved at a dilution rate of 0.07 h(-1), 70 m(2).m(-3) of me mbrane area, and a steady-state biomass concentration of 2.5 g.L-1. The sys tem was stable for over 1250 h. Decreasing the dilution rate led to an incr eased biomass concentration, however, the specific activity was significant ly reduced, and therefore, an optimal dilution rate was determined at 0.055 h(-1). (C) 1999 John Wiley & Sons, Inc.