Rhodococcus rhodochrous PA-34: A potential biocatalyst for acrylamide synthesis

Rhodococcus rhodochrous PA-34 exhibited 55 U mg −1 dcw nitrile hydratase (NHase) activity for the transformation of acrylonitrile to acrylamide. The culture conditions of R. rhodochrous PA-34 for the production of NHase and reaction conditions for this NHase mediated conversion of acrylonitrile to acrylamide were optimised. The maximum production of NHase (2.5 U mL −1 culture) was carried out by culturing R. rhodochrous PA-34 in the medium containing (L −1) 10.0 g glycerol, 5.0 g peptone, 3.0 g yeast extract, 20 mg CoCl 2, pH 7.0, 2 mL propionitrile at 30 °C for 36 h in an incubator shaker (160 rpm). The maximum conversion of acrylonitrile to acrylamide was observed in 100 mM potassium phosphate buffer (pH 7.0), at 10 °C, acrylonitrile (8%, w/v, i.e. 1500 mM) using resting cells of this organism corresponding to 1.6 mg dry cell weight (dcw) mL −1 reaction mixture (specific activity 55 U mg −1 dcw) in 1 h. The resting cells of R. rhodochrous PA-34 retained 76% NHase activity even in the presence of 20% (w/v) acrylonitrile. The conversion of acrylonitrile to acrylamide was carried out at 1 L scale and 600 g (8442 mM) of acrylamide was produced in 12 h at 10 °C.