A novel nitrile-degrading enzyme (nitrile hydratase) from Ralstonia sp. ZA96 isolated from oil-contaminated soils

In this study, a bacterial strain with capable of degrading nitrile compounds was isolated from oil-contaminated soils. Aacrylonitrile removal by the bacterium was analyzed using gas chromatography-mass spectrometry (GCMS). The isolate was identified as Ralstonia sp.ZA96 by biochemical and molecular analyses. Purification of nitrile hydratase from the strain was performed using Q-Sepharose chromatography. The results showed that the 23 kDa-purified enzyme had an optimal activity at pH 8.5 and 25 degrees C. Zn-2 + ion (at 10 mM) and Ca2+ ion (at 2 mM) had a positive and negative effect on the enzyme activity, respectively. Ethylenediaminetetraacetic acid (EDTA) caused a significant reduction in the enzyme activity. The activity in the presence of 5, 5'-dithiobis-(2-nitrobenzoic acid) (DTNB) and dithiothreitol (DTT) was almost maintained, whereas SDS at 10 mM reduced 43% of the enzyme activity. Dimethyl sulfoxide (DMSO) and allyl alcohol had a positive effect on enzyme activity, while chloroform decreased the enzyme activity. The studied enzyme showed a high specificity to aliphatic nitriles including potassium ferrocyanide, potassium hexacyanoferrate, and ammonium thiocyanate. Our results suggest that this nitrile-degrading enzyme had potential to be utilized as a novel candidate for industrial applications.