Simulation and optimization of two-stage continuous stirred tank enzyme reactor system

Abstract

Penicillin amidohydrolase, an enzyme which hydrolyzes benzylpenicillin to give 6-Aminopenicillanic acid and phenylacetic acid, was produced by using $\mbox{\underline{Bacillus}}$ $\mbox{\underline{megaterium}}$ culture. Production of the enzyme from the strain was increased 20 fold by modification of culture medium and the fermentation method. Larger amount of phenyl acetic acid than reported by other investigators was added to the actively growing cell to induce the maximum production of the enzyme. When casitone-containing medium was used, the highest enzyme yield was obtained. Optimal temperature and PH for the activity of bentonite-immobilized penicillin amidohydrolase was 40-45℃ and 8-9, respectively. The performance of two-stage continuous stirred tank enzyme reactor (CSTR) system was evaluated from the results of computer simulation study of the system. The productivity of the reactor system using immobilized enzyme was much higher than using soluble enzyme, which was mainly due to the higher value of product inhibition constant of immobillized enzyme than that of soluble enzyme. The productivity obtained with the two-stage CSTR system was found to be 9.5 m mole of 6-APA per liter of reactor working volume per hour and it was 50% higher than that obtained with the single stage system under the given operational condition. The optical feed concentration of substrate that give the maximum productivity was found to be 0.18 M for 95% conversion requirement and corresponding the first and second stage space time were 10 hours and 8 hours, respectively.