NOVEL THERMOPHILIC BACTERIA PRODUCING NITRILE-DEGRADING ENZYMES

The first known report of the isolation of thermophilic bacteria which produce nitrile-degrading enzymes is presented. One of the strains is olated was studied in detail. Strain Dac521, classified as Bacillus pa llidus, was capable of growth on acetonitrile, benzonitrile, propionit rile, acetamide, benzamide and propionamide as the sole carbon and nit rogen source in minimal nutrient media. The strain produced separate a liphatic-nitrile (e.g. acetonitrile)- and aromatic-nitrile (e.g. benzo nitrile)-degrading activities. Acetonitrile-degrading activity was pro duced constitutively and enzyme production was not enhanced by the add ition of substrate. Under conditions where benzonitrile was the sole c arbon and nitrogen source in minimal nutrient media. acetonitrile-degr ading enzyme activity was completely inhibited and benzonitrile-degrad ing activity was induced. Growth on substrates as sole carbon and nitr ogen sources, together with the substrate specificity of cell-free ext racts, suggested that acetonitrile and benzonitrile degradation may ha ve occurred via nitrile hydratase and nitrilase pathways, respectively . Both the acetonitrile- and benzonitrile-degrading enzyme systems wer e significantly more thermostable in whole-cell preparations and cell- free extracts compared to their mesophilic counterparts.