[Studies on enzymatic synthesis of cephalexin by immobilized penicillin acylase by polyacrylonitrile fibres].

The extracellular penicillin acylase from Bacillus megaterium was immobilized by coupling to derivatives of polyacrylonitrile fibres. The apparent activity of the immobilized enzyme was about 153 U/g (wet weight). The optimal pH and temperature were 6.5 and 40 degrees C for synthesis of cephalexin by penicillin acylase, respectively. Whe the concentration of 7-ADCA was 4% and the ratio of PGME and 7-ADCA and 1:2, the average velocity of synthesis reaction was highest. The optimal supplied amount of immobilized penicillin acylase was 1.125 g/g 7-ADCA.. The apparent Michaelis constant for 7-ADCA was 0.162 mol/L and for PGME was 0.364 mol/L, Vmax was 0.0462 mol.L-1.min-1 at 30 degrees C and pH6.5. The remained activity was about 83.9% after operating 50 times.