Efficient hydration of 2-amino-2,3-dimethylbutyronitrile to 2-amino-2,3-dimethylbutyramide in a biphasic system via an easily prepared whole-cell biocatalyst†
From an environmental perspective, utilizing nonconventional solvents (i.e. green solvents) with low ecological footprints is a highly beneficial alternative to using conventional organic solvents to form a reaction system. The nitrile hydratase (NHase, EC 126.96.36.199) catalyzed hydration of 2-amino-2,3-dimethylbutyronitrile (ADBN) to 2-amino-2,3-dimethylbutyramide (ADBA) in various green solvent–aqueous reaction systems was investigated in this study. After systematically optimizing the reaction conditions, the HFE-7100/H2O (v/v, 10%) biphasic system was ultimately identified as a promising reaction system for reducing product inhibition, avoiding substrate hydrolysis, and facilitating product separation and solvent recovery. The average ADBA yield of an entire batch reaction was 97.3%, which is obviously higher than those obtained with previously reported chemical or enzymatic methods. This is the first attempt to apply a fluorous solvent–aqueous biphasic system to a biocatalytic process, and the results suggest that the fluorous solvent employed in the biphasic system satisfies the requirements for green chemistry.