APPLICATION OF POROUS MICROSPHERES PREPARED BY SPG (SHIRASU PORUS GLASS) EMULSIFICATION AS IMMOBILIZING CARRIERS OF GLUCOAMYLASE (GLUA)

Fairly uniform spheres of crosslinked polystyrene (PS) and polymethyl methacrylate (PMMA), prepared by a particular emulsification process u sing SPG (Shirasu Porous Glass) membranes and subsequent suspension po lymerization, were applied for immobilizing carriers of Glucoamylase ( GluA). A mixture of monomers, solvents, and oil-soluble initiator was allowed to permeate through the micropores of SPG, suspended in an aqu eous solution of poly(vinyl alcohol), and polymerized while retaining the narrow size distribution during polymerization. A small amount of acrylic acid or glycidyl methacrylate (GMA) was incorporated for the i mmobilization of GluA via covalent bonding. Although GluA has been reg arded as being difficult to retain its activity after the immobilizati on process, a porous structure of the carriers definitely favored the immobilization, and a maximum 55% relative activity (RA) was obtained by the physical adsorption to PMMA spheres. The reaction of epoxide in GMA with 6-aminocaproic acid provided a spacer arm for the carboxyl g roup. An improvement of activity was expected by the incorporation of the spacer arms; however, barely noticeable activity was observed for PMMA carriers either by the physical adsorption or by the covalent bon ding. A slight improvement was observed for PS carriers with spacers c ompared to the carriers without them. The diffusion process of oligosa ccharides in the porous carriers seemed to retard the rate of hydrolys is in the case of largest carriers, 60 mu m PS-DVB-AA spheres. The act ivity of immobilized GluA was retained during a long storage period of more than 150 days, some of them even increasing gradually, while the activity of native GluA dropped to zero after 100 days. (C) 1997 John Wiley & Sons, Inc.