Acrylonitrile degradation by whole cells of Corynebacterium sp. D5, isolated from polluted industrial waste

Acrylonitrile is a toxic organo-cyanide compound extensively used as solvents and in the manufacture of plastics, polymers, synthetic fibers, resin, dyestuffs, pharmaceuticals and vitamins. Because of its acute neurotoxicity, mutagenicity, carcinogenicity and teratogenicity, discharge of acrylonitrile contained wastewater can lead to serious environmental pollution if is not controlled. Microbial degradation has been considered as a way of removing highly toxic nitriles from industrial waste. In our studies, the biodegradation of acrylonitrile was demonstrated by using whole cells of Corynebacterum sp. D5 isolated from polluted industrial wastewater. Although the bacterium could not utilized the compound as a source of carbon, energy and nitrogen for its growth, Corynebacterium sp. D5 was capable to degrade acrylonitrile (CH₂=CH-CN) into acrylamide (CH₂=CH-CONH₂) and acrylic acid (CH₂=CH-OOH). The acrylonitrile degradation took place via a two-steps reaction invoving nitrile-hydratase and amidase. During the degradation, the highest nitril hydratase activity was 4.894 nmol.(min.mg) ⁻¹ with the optimum temperature and pH was 25°C and pH 7.0, while the highest amidase acivity was 1,315 nmol.(min.mg) ⁻¹, with the optimum temparature and pH was 50°C and pH 6.0, respectively. Besides on acetonitrile as inducer, Corynebacterium sp. D5 was also able to grow on various saturated low molecular weight of nitrile and amide compounds.