A metal ion-based method for the screening of nitrilases

In this paper we describe a colorimetric method for the screening of nitrilases. When a buffered solution of CoCl2 is added to a nitrilase-catalyzed hydrolysis reaction, the ammonia product forms a complex with the cobalt ion resulting in a color change from light pink to yellow, which can readily be quantified using a spectrophotometer at 375 nm. This method has been demonstrated for both wild-type and evolved nitrilases.