Efficient biosynthesis of β-alanine with a tandem reaction strategy to eliminate amide by-product in the nitrilase-catalyzed hydrolysis

Abstract

An efficient biosynthesis of β-alanine from 3-aminopropionitrile at high concentration has been developed using a one-pot bienzymatic cascade of a nitrilase and an amidase. The nitrilase BjNIT3397 from Bradyrhizobium japonicum strain USDA110 catalyzes the hydrolysis of 3-aminopropionitrile to β-alanine at the concentration up to 3.0mol/L with the formation 23% of 3-aminopropanamide. In order to eliminate the by-product 3-aminopropanamide, we cloned and characterized a new amidase from Pseudomonas nitroreducens through gene mining. Under the optimal conditions (50mmol/L Na2HPO4-NaH2PO4 buffer, pH 6.0, 40°C), 2.0mol/L (176g/L) of 3-aminopropanamide was completely hydrolyzed within 12h. A tandem reaction system was then established to eliminate the by-product 3-aminopropanamide and increase the production of β-alanine to 90% isolated yield with 15.02g/(L.h) space-time-yield. These results demonstrated that the tandem reaction strategy was an effective method of eliminating the amide by-products in the nitrilase-catalyzed hydrolysis at high substrate concentration.