beta - lactam antibiotics are synthesized by reacting an amino - beta - lactam component with a corresponding amino - group - containing acylating side - chain component in the presence of penicillin amidase from e . coli covalently immobilized on support particles . the resulting beta - lactam antibiotic product is solubilized by adding an acid such as sulfuric acid to lower the ph to 1 . 0 at a temperature in the range of 0 ° c . to + 5 ° c . the immobilized penicillin amidase is substantially inactivated by the acid . after separating the beta - lactam antibiotic product , the immobilized penicillin amidase is substantially reactivated for reuse in antibiotic synthesis by treatment with a buffer having about a neutral ph . antibiotics that can be produced include ampicillin , amoxicillin , cephalexin , cefaclor and cefadroxil . support particles that can be used include particles having a macroporous structure and a particle diameter of 10 - 1000 μm , particles having oxirane groups , particles made of a synthetic polymer and inorganic particles such as porous glass particles .