SURFACTANT-INDUCED BREAKTHROUGH EFFECTS DURING THE OPERATION OF 2-PHASE BIOCATALYTIC MEMBRANE REACTORS

Surface-active components, both reactants and products, are frequently encountered in two-phase, aqueous-organic, biocatalytic reactions. Wh en such reactions are carried out in a membrane reactor, employing a m embrane selectively wetted by one of the two reactants, changes in the content of these surfactants-as a consequence of the progress of the reaction-can lead to wetting transitions at the two membrane-liquid in terfaces as a result of adsorption of the tenside. This can lead to a decrease in the pressure required to cause the, initially, nonwetting phase to break through the membrane. Such effects render difficult the operation of two-phase membrane bioreactors. Hence, it is necessary t o make a careful selection of the membrane material and type by consid ering factors such as UF versus MF and low MWCO versus high MWCO to en able the reactor to be operated without breakthrough, but without sign ificantly compromising the reaction rates that can be maintained. The phenomena leading to breakthrough effects are discussed in this paper, and experimental results for the hydrolysis of ethyl laurate by lipas e from Candida rugosa in a batch flat sheet membrane reactor are prese nted with the reactor operated with a variety of membranes. An experim ental result showing the decrease in the pressure required to cause br eakthrough of the organic phase (for the system ethyl laurate-lauric a cid-water) as the content of the highly surface-active lauric acid in the organic phase is increased is also presented for an asymmetric, hy drophilic meta-aramid ultrafiltration membrane. (C) 1994 John Wiley & Sons, Inc.