Effects of preparation variables of enzyme-encapsulating water-in-oil emulsion on enzymatic reaction conversion and emulsion stability in an enzyme-emulsion-liquid-membrane reactor

The effects of various water-in-oil (W/O) emulsion preparation variables, s uch as water-to-oil volume ratio of W/O emulsion, emulsification speed and time, and emulsifying agent concentration, on the permeation rates of L-phe nylalanine methyl ester (L-PME, substrate) and L-phenylalanine (L-Phe, prod uct) were investigated in an enzyme-emulsion-liquid-membrane (EELM) system accompanying the hydrolysis of the substrate into the product. The permeati on rate of the substrate was higher in the system with a higher water-to-oi l volume ratio or lower emulsification energy, while emulsifying agent conc entration had Little influence on its permeation rate as far as emulsion wa s stable. The permeation rate of the product was highest in the system with water-to-oil ratio of 1/1, the lowest emulsification energy or 7 wt.% emul sifying agent concentration. This is because the rate was dependent only on the mass transfer resistance, such as surfactant layer resistance at inter faces, membrane thickness, and the mass transfer area between external phas e and emulsion drops. The explanation was supported by the experimentally m easured data of emulsion drop size, emulsion viscosity, and internal drople t size. Finally, the optimum permeation rate was obtained at 7 wt.% emulsif ying agent concentration, water-to-oil volume ratio of 1/1 and emulsificati on speed of 6000 rpm for 15 min. (C) 1999 Elsevier Science S.A. All rights reserved.