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

摘要

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.