Nitrile hydratase‐mediated conversion of acrylonitrile by Rhodococcus rhodochrous ( RS ‐6)

Abstract BACKGROUND Acrylamide is an important monomer for the synthesis of polyacrylamide, which has wide applications in industries. This molecule can be produced by the hydration of acrylonitrile, catalyzed by the enzyme nitrile hydratase (NHase) secreted by microorganisms. Herein, synthesis of acrylamide was carried out by soil isolate Rhodococcus rhodochrous (RS‐6) contains NHase. The critical parameters affecting the bioconversion process such as pH, temperature, substrate concentration, resting cell concentration and acrylamide concentration were optimized by changing one parameter at a time. RESULTS The optimum conditions for acrylonitrile conversion to acrylamide were observed at pH 7.0, temperature 15 °C, substrate concentration 1250 mmol L–1 and 1.4 mg dcw mL–1 concentration of resting cells. Under these improved conditions the entire bioconversion of acrylonitrile to acrylamide was observed within 75 min of incubation. The NHase of resting cells of R. rhodochrous (RS‐6) showed tolerance to acrylonitrile (7% w/v) and acrylamide up to 30%. Laboratory‐scale production by fed‐batch method resulted in an accumulation of 574 g L−1 acrylamide in 9 h. CONCLUSION The NHase‐containing resting cells of R. rhodochrous (RS‐6) catalyzed the maximum conversion of acrylonitrile to acrylamide under optimized conditions. © 2020 Society of Chemical Industry