Stabilization and reutilization of Bacillus megaterium glucose dehydrogenase by immobilization

Glucose dehydrogenase (GDH) from Bacillus megaterium was immobilized using aminopropyl controlled-pore silica (CPS, average pore sizes of 170 and 500 A) as a support and glutaraldehyde as a bifunctional crosslinking agent. The CPS-immobilized enzyme could be reused 12 times and the best results were obtained using aminopropyl CPS-500 and bovine 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 several times and were thermostable at 40 degrees C for 7 h. The kinetic parameters as Michaelis constant and maximum rate were determined for the immobilized enzyme and compared with those for the freeform.