Production of Acrylamide using Alginate‐Immobilized E. coli Expressing Comamonas testosteroni 5‐MGAM‐4D Nitrile Hydratase

A thermally‐stable nitrile hydratase produced by Comamonas testosteroni 5‐MGAM‐4D has been expressed in Escherichia coli, and the alginate‐immobilized transformant evaluated as catalyst for the conversion of acrylonitrile to acrylamide. In batch reactions with catalyst recycle, the catalyst productivity decreased with increasing acrylonitrile concentration or reaction temperature, but was relatively insensitive to acrylamide concentration. A total of 206 consecutive batch reactions with catalyst recycle were run at 5 °C and produced 1035 g acrylamide/g dry cell weight and 95 g acrylamide/L; the initial and final volumetric productivities of this series of recycle reactions were 197 and 96 g acrylamide/L/h, respectively. A packed column reactor yielded lower catalyst productivity than consecutive batch recycle reactions, presumably due to contact of the fixed‐bed catalyst with a constant high concentration of acrylonitrile.