Abstrato

Biotransformation of 3-cyanopyridine by utilizing free and immobilized whole cell nitrilase enzyme from Nocardia globerula NHB-2.

Hariharan P, Sudha AS, Agilandeswari K

Nitrile hydrolysing enzymes are potential biocatalyst for direct conversion of toxic nitriles into nontoxic and high value amides and acids. The microorganism Nocardia globerula NHB-2 was grown and induced with three different short chain aliphatic nitriles and exhibited activity towards aromatic nitriles observed. Propionitrile was found to be the optimal inducer for this microorganism at a concentration of 0.3% v/v. Three factor Box Behnken design was used to optimize the reaction parameters for the biotransformation of 3-cyanopyridine to nicotinic acid. The optimized conditions include substrate concentration of 210 mM, resting cell concentration of 30 U/mg DCW and time of conversion of 70 min. Then, immobilization of the resting cells of Nocardia globerula NHB-2 with agar was performed and the nitrilase activity was compared with that of the free resting cells in terms of thermal stability. Packed bed reaction system of the immobilized cells was utilised for the production of nicotinic acid in a continuous operation wherein the substrate is recycled. The immobilized resting cells were reused four times and the residual nitrilase activity observed was 40% up to the third recycle.