Efficient enzymatic synthesis of cephalexin in suspension aqueous solution system.

An efficient method for the enzymatic synthesis of cephalexin (CEX) from 7-amino-3-deacetoxycephalosporanic acid (7-ADCA) and d-phenylglycine methyl ester (PGME) using immobilized penicillin G acylase (IPGA) as catalyst in a suspension aqueous solution system was developed, where the reactant 7-ADCA and product CEX are mainly present as solid particles. The effects of key factors on the enzymatic synthesis were investigated. Results showed that continuous feeding of PGME was more efficient for the synthesis of CEX than the batch mode. Under the optimized conditions, the maximum 7-ADCA conversion ratio of 99.3% and productivity of 200 mmol/L/H were achieved, both of which are much superior to the homogeneous aqueous solution system. Besides, IPGA still retained 95.4% of its initial activity after 10 cycles of enzymatic synthesis, indicating the excellent stability of this approach. The developed approach shows great potential for the industrial production of CEX via an enzyme-based route.