STABILIZATION AND REUTILIZATION OF BACILLUS-MEGATERIUM GLUCOSE-DEHYDROGENASE BY IMMOBILIZATION

Glucose dehydrogenase (GDH) from Bacillus megaterium was immobilized u sing aminopropyl controlled-pore silica (CPS, average pore sizes of 17 0 and 500 Angstrom) as a support and glutaraldehyde as a bifunctional crosslinking agent. The CPS-immobilized enzyme could be reused 12 time s and the best results were obtained using aminopropyl CPS-500 and bov ine serum albumin as a feeder for stabilizing the protein layer on the support. DEAE-Sephadex (A-25 and A-50) was also used as a support for immobilizing GDH, with yields of around 42% for A-25 and 25-30% for A -50. The effect of pH on the immobilization procedure showed pH 6.5 to be better than pH 7.5 with respect to the recovery of enzyme activity . Both preparations of DEAE-Sephadex immobilized GDH could be reused s everal times and were thermostable at 40 degrees C for 7 h. The kineti c parameters as Michaelis constant and maximum rate were determined fo r the immobilized enzyme and compared with those for the freeform.