Isolation and Characterization of a Nitrilase-Producing Geotrichum Strain and Optimization of the Fermentation Conditions.

Glufosinate ammonium is a fast-acting herbicide that was originally discovered as a natural product and is currently the only herbicide that targets glutamine synthetase. Nitrilase was found to catalyze synthesis of glufosinate ammonium. In this study, a fungus, Ytz23, with higher nitrilase activity, was isolated from seabed silt samples and was found to belong to the Geotrichum genus based on morphological, biochemical, and molecular characterization. It was found that Ytz23 had high specificity for the catalysis of fatty nitriles, including acrylonitrile, 3-aminopropanenitrile, and 2-amino-4-(hydroxymethylphosphono)-butanenitrile. The optimal concentrations of variables in the fermentation reaction were assessed. It was found that the optimal carbon and nitrogen sources were glycerol 20 g/L, yeast extract 20, and 0.2 g/L of 2-amino-4-(hydroxymethylphosphono)-butanenitrile, with optimal fermentation conditions of pH 7.0, 30 °C, and shaking at 220 rpm. Under these optimal conditions, the enzyme activity of the nitrilase was 10.2 U/mL. These findings provide a basis for the biosynthesis of glufosinate ammonium and have potential for application in the industrial production of glufosinate ammonium.