Abstract
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)), MgSO(4) (0. 5 g l(-1)), K(2)HPO(4) (0.6 g l(-1)), urea (9.0 g l(-1)), and CoCl(2) (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.