Screening method for detecting amidase and nitrile hydratase activity and use thereof

A screening method for detecting amidase or nitrile hydratase activity, which comprises

• a) preparing on a suitable support a replica of cell colonies which express amidases or nitrile hydratases and which have grown on a suitable, solidified medium, followed by,
• b1) in the case of colonies having nitrile hydratase genes to be assayed, firstly incubating the cells adhering to the support with a substrate solution composed of a nitrile of the formula (I) R—CN in which R is a C1-C20-alkyl, C6-C20-aryl or C5-C20-heteroaryl radical which is unsubstituted or mono- or poly-substituted with substituents inert under the reaction conditions and of a buffer, and subsequently
• b2) carrying out an incubation with a buffered hydroxylammonium salt solution, or,
• c) in the case of cell colonies having amidase genes to be assayed, incubating the colonies adhering to said support with a substrate solution composed of an amide of the formula (II) R—CONH2, in which R is as defined above, a hydroxylammonium salt and a buffer, and then,
• d) following b2) or c), staining the active colonies by transferring the support to an iron (III) salt solution, and
• e) isolating, where appropriate, cells of said active colonies from said support or from the original areas in which said colonies have been present on the solidified medium.