Date Published: June 22, 2016
Publisher: Springer Berlin Heidelberg
Author(s): Ismailsab Mukram, Masarbo Ramesh, T. R. Monisha, Anand S. Nayak, T. B. Karegoudar.
A nitrile utilizing bacterium Rhodococcus sp. MTB5 was previously isolated in our laboratory by the enrichment culture technique. It is able to utilize butyronitrile as sole carbon, nitrogen, and energy source. Maximum butyronitrile degrading property of this strain has been investigated. Results reveal that 100, 98, and 88 % degradation was achieved for 2, 2.5, and 3 % butyronitrile, respectively. The strain is capable of growing in as high as 5 % butyronitrile concentration. A two-step pathway involving nitrile hydratase (NHase) and amidase was observed for the biodegradation of butyronitrile. Complete degradation (mineralization) of butyronitrile with the help of metabolite feeding experiment was reported. The significance of this investigation was the capability of the strain to completely degrade and its ability to grow on higher concentrations of butyronitrile. These potential features make it a suitable candidate for practical field application for effective in situ bioremediation of butyronitrile contaminated sites.
Nitriles are the cyanide containing compounds (R–CN) and are widespread in the environment as a result of biological and industrial activity (Legras et al. 1990). They are used as preliminary materials for the synthesis of a numerous fine chemicals (Banerjee et al. 2002). Butyronitrile is an aliphatic nitrile, clear colourless liquid with a suffocating odour resembling bitter almond oil. It is miscible with most polar organic solvents, hence finds applications in the industries in making other chemicals. It is mainly used as a precursor to the poultry drug amprolium (Peter et al. 2002). Amprolium is a coccidiostat (antiprotozoal agent) used in the poultry that acts upon coccidia parasites. Amprolium is prepared using commercially available butyronitrile as starting material. It is also used in electrolyte composition in dye-sensitized solar cells (Sauvage et al. 2011). A number of nitriles have been reported as potent carcinogenic, mutagenic, and toxic in nature (Ramakrishna et al. 1999). The use of nitriles as bulk solvents has increased their distribution in the environment and needs their remediation (Ebbs 2004). The chemical hydrolysis of these compounds necessitates harsh conditions, such as extremes of pH and elevated temperatures with the creation of significant quantities of by-products and secondary pollutants (Kobayashi and Shimizu 2000; Prasad et al. 2009). Bioremediation is one such method used for the detoxification of contaminated sites. It is an inexpensive technology, and can either eliminate these compounds by degrading them to harmless intermediates or, in due course, to carbon dioxide and water (Nawaz et al. 1991).
As per the available literature, the degradation of aliphatic nitriles follows through NHase and amidase pathway (Santoshkumar et al. 2011). Large numbers of reports are available on the degradation of aliphatic nitriles and most of them are on acetonitrile (Sorokin et al. 2007; Manolov et al. 2005; Feng and Lee 2009). However, only limited reports are available on the degradation of butyronitrile (Wenzhong et al. 1991; Nawaz et al. 1992), and among them, most reports are on the growth of the microorganisms on butyronitrile as carbon and/or nitrogen source (Nawaz et al. 1989; Linardi et al. 1996; Kao et al. 2006).