For production of 6-aminopenicillanic acid by enzymatic hydrolysis of benzylpenicillin, two-stage continuous stirred tank enzyme reactor system was evaluated. Using proper mathematical model of the reaction kinetics and kinetic constants of soluble and immobilized forms of penicillin amidohydrolase, the reactor system was simulated with an aid of a computer and a set of optimum operating conditions was found. In comparison with the single stage system, the productivity of the two-stage enzyme reactor system was 50 % higher than that of the single stage system under the same operating conditions. For the industrial applications, the reactor system using immobilized penicillin amidohydrolase was found to be far more advantageous in terms of productivity than that using soluble enzyme because of the reduced inhibitory effect of the product, 6-aminopenicillanic acid, on the immobilized enzyme as compared to the same effect on the soluble enzyme.