Overview of screening for new microbial catalysts and their uses in organic synthesis--selection and optimization of biocatalysts.

As a typical example of screening for a microbial biocatalyst from nature, isolation of aldoxime-degrading microorganisms, characterization of a new enzyme phenylacetaldoxime dehydratase, and application of this enzyme to nitrile synthesis are described. The pathway in which aldoximes are successively degraded via nitrile in microorganisms could be named as 'aldoxime-nitrile pathway'. As an example of a post-screening procedure, a directed molecular evolution technique was successfully used to change the properties of nucleoside pyrophosphate phosphotransferase to make it suitable for synthesis of inosine-5'-monophosphate (5'-IMP). With the mutant enzyme, the efficiency of the production of 5'-IMP, a food additive, was much improved.