Efficient access to l-phenylglycine using a newly identified amino acid dehydrogenase from Bacillus clausii

摘要

An amino acid dehydrogenase from Bacillus clausii ( Bc AADH) was identified and overexpressed in Escherichia coli BL21(DE3) for the preparation of L -phenylglycine from benzoylformic acid. Recombinant Bc AADH was purified to homogeneity and characterized. Bc AADH could catalyse reductive amination and oxidative deamination at optimum pHs of 9.5 and 10.5. Furthermore, Bc AADH has a broad substrate spectrum, displaying activities toward various aromatic and aliphatic keto acids. When coexpressed with glucose dehydrogenase from Bacillus megaterium , the potential application of Bc AADH in the preparation of L -phenylglycine was investigated at a high substrate loading and low biocatalyst addition. As much as 400 mM benzoylformic acid could be fully reduced into L -phenylglycine within 6 h at >99.9% ee . With merely 0.5 g DCW L ~(?1) , 200 mM benzoylformic acid was completely reduced, resulting in a substrate to biocatalyst ratio of 60 g g ~(?1) , environmental factor of 4.7 and 91.7% isolation yield at gram scale. This study provides guidance for the application of Bc AADH in the synthesis of chiral non-natural amino acids.