HIGH SPECIFIC ACTIVITY OF WHOLE CELLS IN AN AQUEOUS-ORGANIC 2-PHASE MEMBRANE BIOREACTOR

Whole Bacillus subtilis cells can catalyze stereoselective hydrolysis of menthyl acetate in a small-scale two-phase membrane bioreactor. A l ayer of cells was deposited on one side of a 0.2 mu m microporous nylo n membrane and then neat liquid racemic menthyl acetate was circulated past the same side. This organic phase was pressurized slightly relat ive to the aqueous buffer which flowed past the other face of the memb rane. No breakthrough or cell detachment was observed over 24 h operat ion. The total reaction rate reached a maximum with a cell layer of ab out 40 mu m, then declined far thicker layers. The specific activity ( per unit biomass) at the maximum was about five times higher than with the same cells in an emulsion reactor. This probably reflects continu ous good contact with both phases. (C) 1998 Elsevier Science Inc.