A nitrilase-producing strain ZJUTB06-99, capable of bicitransforming acrylonitrile into acrylic acid, was newly isolated from soil samples. Based oil the morphology, physiological tests, ATB system and its 16S rDNA sequence, strain ZJUTB06-99 was identified as Arthrobacter nitroguajacolicus. Optimal reaction conditions were investigated by the manipulation and measurement of various parameters including pH, temperature and certain cationic metals. The highest nitrilase activity was obtained when reaction was carried out at a pH of 6.5 phosphate buffer and in temperature of 40 degrees C water bath. The nitrilase of A. nitroguajacolicus ZJUTB06-99 exhibited excellent thermostability. Nitrilase activity was strongly inhibited by Hg(2+), Ag(+) and Cu(2+), but Ni(2+) and Ca(2+) increased enzyme activity to 163% and 158%. respectively. The investigation of substrates spectrum showed that A. nitroguajacolicus ZJUTB06-99 exhibited the highest nitrilase activity towards aromatic nitriles Such as phenylacetonitrile. However, no detectable activity was recorded when any of the tested amides were used as substrates. (C) 2009 Elsevier Ltd. All Lights reserved.