Multi-enzyme immobilization in eeo-friendly emulsion liquid membrane reactor - a new approach to membrane formulation

Multi-enzymes (a-glucosidase and glucose oxidase) have been immobilized in emulsion liquid membranes for using such membranes as eco-friendly enzyme emulsion liquid membrane (EELM) reactors. Role of surfactant-stabilized liquid membranes as separation-concentration devices changes here to that of promising, eco-friendly reactors where product is transported to the external phase thereby eliminating the need for demulsification for subsequent recovery of product and membrane phase material for reuse. Thus tradeoffs among stability, selective permeability and ease of demulsification get significantly modified necessitating a new approach to membrane formulation. With this new approach to membrane formulation, the present investigations have been carried out. Stability aspect has been studied measuring leakage through such membranes using a tracer technique while permeability has been measured during actual enzymatic reactions inside the emulsion globules and transportation of the product outside the membranes. Effects of agitation, surfactant concentration, internal phase volume fraction, membrane phase material and non-Newtonian conversion of membrane phase on the stability of liquid membranes, as well as product generation and permeation have been investigated. In presence of carrier and additional stabilizer (polystyrene 1% by wt.), emulsion liquid membranes have been found to yield the best results with a surfactant concentration of 3.5-4 wt.% at an agitation of 300 rpm and with an internal phase volume fraction of 0.5. The findings are expected to be very useful in developing emulsion liquid membranes as efficient enzyme-encapsulating bioreactors. (C) 2002 Elsevier Science B.V. All rights reserved.