Penicillin G acylase from Achromobacter sp. (NPGA) was studied in the enzymatic synthesis of beta-lactam antibiotics by kinetically controlled N-acylation. When compared with penicillin acylase of Escherichia coli (PGA), the NPGA was significantly more efficient at syntheses of ampicillin and amoxicillin (higher S/H ratio and product accumulation) in the whole range of substrate concentrations. The degree of conversion of 6-aminopenicillanic acid to amoxicillin and ampicillin (160 mM 6-APA, 350 mM acyl donor methylestera <...HCl, pH 6.3, 25 A degrees C, reaction time of 200 min) with immobilized NPGA equaled 96.9 % and 91.1 %, respectively. The enzyme was highly thermostable with maximum activity at 60 A degrees C (pH 8.0) and 65 A degrees C (pH 6.0). Activity half-life at 60 A degrees C (pH 8.0) and at 60 A degrees C (pH 6.0) was 24 min and 6.9 h, respectively. Immobilized NPGA exhibited long operational stability with half-life of about 2,000 cycles for synthesis of amoxicillin at conversion conditions used in large-scale processes (230 mM 6-APA, 340 mM d-4-hydroxyphenylglycine methylestera <...HCl, 27.5 A degrees C, pH 6.25). We discuss our results with literature data available for related penicillin acylases in terms of their industrial potential.