Isolation of Pseudomonas granadensis B6 with (+)-γ-lactamase and whole cell resolution of racemic γ-lactam

Abstract

We have isolated a strain that can produce (+)-γ-lactamase to hydrolyze racemic (+/−)-γ-lactam from several soil samples using (+/−)-γ-lactam as the only carbon source. We have identified this strain to be Pseudomonas granadensis B6. We further optimized the enzyme fermentation and biotransformation conditions for the γ-lactamase from P. granadensis B6. We found that glucose was the optimum carbon source and ammonium oxalate the optimum nitrogen source; P. granadensis B6 showed good growth at pH values ranging from 3 to 10, with an the optimum fermentation pH between 7 and 8, and the optimum biotransformation pH was 8. The optimum fermentation temperature was determined to be 30°C and the optimum biotransformation temperature was 40°C. We successfully used P. granadensis B6 with (+)-γ-lactamase to rapidly resolve 100g (+/−)-γ-lactam/L and found that it could tolerate up to 300g (+/−)-γ-lactam/L as substrate, with the activity of P. granadensis B6 enzyme reaching 1280±30.4U/mg.