Acetonitrile Biotransformation into Less Toxic Compounds by a Bioprocess Based on the Nitrile Hydratase/Amidase Sequential Enzymatic Reactions

Abstract

The nitrile hydratase/amidase in-situ sequential enzymes of Microbacterium imperiale CBS 498-74 were used, as biocatalysts, for the biotransformation of acetonitrile streams into less toxic compounds: the corresponding acetamide and acetic acid. This preliminary study aimed to investigate the possible use of resting cells of this strain for pollutant removal. The kinetic parameters, KM and Vmax, evaluated in batch reactor, at 20 °C, and in 50 mM sodium phosphate buffer, at pH 5.0 and 7.0, were at pH 5.0, 60.4 mM (or at pH 7.0, 74.96 mM) and 0.44 µmol min-1 mgDCW-1 (or at pH 7.0, 0.46 µmol min-1 mgDCW-1), respectively. The reactions were unaffected in the whole range of pH, 3.5 till 8.5. Acetonitrile biotransformation, up to 300 mM, into the corresponding acetamide and acetic acid was driven to completeness, at steady state, in Continuous Stirred UF-Membrane Reactor (CSMR). The importance of stirring was also assessed.