Study on the screening of lactamase and its fermentation conditions
产γ_内酰胺水解酶菌株的筛选及发酵条件研究

(-)-gamma-Lactam is one of the key starting materials for the synthesis (-)-cabovir and (-)-abacavir, which serve as two powerful antiviral agents. The production of gamma-lactam using enzymatic resolution of racemic gamma-lactam was attempted in the paper. 20 out of 69 strains capable of producing lactamase were screened from soil samples collected in several districts throughout Beijing; particularly N-actylphenylalanine was used as sole carbon source in the screening method. It was found by chiral HPLC analysis that strain L29-9 was able to enantioselectively hydrolyze the (+)-isomer in the racemic lactam, thus giving the desired (-)-gamma-lactam with high enantiomeric excess (> 70%). Ferment conditions of strain L29-9, including carbon source, nitrogen source, pH, and culturing time, were studied and the optimum conditions were as follows: citric acid 2 g/L, yeast extract 5 g/L, pH 7.0, culturing for 40h. Biotransformation using whole cells of the strain was inducted at 30 degrees C for 12h, giving (-)-gamma-lactam as enantiopure product with yield up to 40% and 99.5% e.e.