Bioconversion of acrylonitrile using nitrile hydratase activity of Bacillus sp. APB-6

Bacillus sp. APB-6 harboring nitrile hydratase was used in the production of acrylamide from acrylonitrile. Bacillus sp. APB-6, for maximum production of Co⁺⁺ containing nitrile hydratase, was cultured in the medium containing lactose (18.0 g l^-1), peptone (1.0 g l^-1), yeast extract (2.0 g l^-1), MgSO₄ (0. 5 g l^-1), K₂HPO₄ (0.6 g l^-1), urea (9.0 g l^-1), and CoCl₂ (0.01 g l^-1), pH 7.0, and incubated at 35 °C for 24 h in an incubator shaker (160 rpm). Nitrile hydratase exhibited relatively high specificity for aliphatic nitriles. Free cells were immobilized using 2% (w/v) agar solution to enhance enzyme stability and reusability in repetitive cycles of acrylamide production. Under optimized conditions, nearly complete bioconversion of acrylonitrile was achieved with a fair recovery of 85% using free and immobilized cells equivalent to 500 mg dcw l^-1. An efficient nitrile hydratase-mediated bioconversion of acrylonitrile to acrylamide at 1-l scale was achieved with time and space productivity of 426 g h^-1 g^-1 dcw using free cells.