Abstract

Two bacterial species Rhodococcus rhodochrous and Rhodococcus fascianswere evaluated for the production of nitrilase enzyme (EC 3.5.5.2) from benzonitrile. This is the first time report on comparative analyses of intracellular nitrilases in two different Rhodococcus species which showed the involvement of periplasmic nitrilases towards nitrile degradation rather than cytoplasmic nitrilases. The periplasmic nitrilases of R. rhodochrous showed nearly 50% more activity as compared to R. fascians. In comparison to R. fascians, R. rhodochrous was found to be better towards nitrile production and degradation as observed under different physiological conditions. The optimum nitrile degradation was recorded at 40ËšC and at pH 8.0. The nitrilase enzyme produced by R. rhodochrous was found to be fairly thermostable, as an incubation temperature of 45ËšC did not affect the activity of nitrilase enzyme produced by it adversely. The pre-incubation temperature resulted in a decrease of nitrilase activity. The substrate concentration of 40 mM was found to be optimum for hydrolyzing benzonitrile. These findings may prove beneficial from enzymology and industrial biotechnology point of view so as to render both the environment free from harmful nitrile compounds.

Key words:  Benzonitrile, cytoplasmic, periplasmic, nitrilase, rhodococcus