Enzymatic Synthesis of Amoxicillin via a One-pot Enzymatic Hydrolysis and Condensation Cascade Process in the Presence of Organic Co-solvents

A cascade reaction combining the enzymatic hydrolysis of Penicillin G potassium salt (PGK) with the kinetically controlled enzymatic coupling of in situ formed 6-aminopenicillanic acid (6-APA) with p-hydroxyphenylglycine methyl ester (D-HPGM) to give amoxicillin as the final product by using a single enzyme has been demonstrated successfully. Ethylene glycol (EG) was employed as a component of reaction buffer to improve the synthesis yield. Reaction parameters, including different cosolvents, EG content, the loading of immobilized penicillin G acylase (IPA), and reaction temperature and time were studied to evaluate their effects on the reaction. The best result of 55.2% yield was obtained from the reaction which was carried out in the mixed media containing 40% sodium dihydrogen phosphate buffer (apparent pH 6.0) and 60% EG (v/v), with the initial concentration 150 mM and 450 mM of PGK and D-HPGM, respectively, catalyzed by 50 IU/mL IPA at 25 C for 10 h. The IPA could be recycled for nine batches without obviously losing of catalytic activity. The important strategy will have potential application in the beta-lactam antibiotics industry due to the advantages of saving the effort of isolating 6-APA, reducing usual enzymatic steps and the industrial cost of amoxicillin synthesis.