Immobilization of Candida cylindracea lipase on colloidal liquid aphrons (CLAs) and development of a continuous CLA-membrane reactor.
A novel technique is described for the immobilization of Candida cylindracea lipase in the soapy-shell of colloidal liquid aphrons (CLAs). CLAs consist of a micron-sized solvent droplet surrounded by a thin, aqueous, soapy-film and are stabilized by a mixture of nonionic and ionic surfactants. Retention of lipase within the CLAs is primarily determined by electrostatic interactions between the surface charges on the protein and those of the anionic surfactant used (SDS) because leakage of the lipase from dispersed CLAs was reduced at low continuous phase pH (<pl). Leakage was also reduced after successive dispersions and at higher enzyme loading; this latter point suggests that hydrophobic interactions became important as the surface area per molecule increases. The activity of both free and CLA-immobilized lipase was also determined for the hydrolysis of p-nitrophenyl acetate and p-nitrophenyl caprylate at various substrate concentrations and continuous phase pH. The CLA immobilized lipase displayed a broader optimum pH range in both cases and, due to mass transfer limitations, did not exhibit a normal Michaelis-Menten dependence on substrate concentration. Finally, the possibility of scaling-up this new technique was demonstrated by the use of a cross-flow membrane reactor for continuous product separation and recycle of the CLA-immobilized enzyme. (c) 1996 John Wiley & Sons, Inc.
Lye
G J
GJ
Department of Chemical Engineering and Chemical Technology, Imperial College of Science, Technology and Medicine, Prince Consort Road, London, SW7 2BY, UK.
Pavlou
O P
OP
Rosjidi
M
M
Stuckey
D C
DC