From enzymes to designer bugs in reductive amination:: A new process for the synthesis of L-tert-leucine using a whole cell-catalyst

A whole-cell-catalyst for the asymmetric reductive amination of a-keto acids has been developed and applied for the synthesis of the non-proteinogenic alpha-amino acid L-tert-leucine. Besides the economical whole-cell catalyst, bearing a leucine dehydrogenase from Bacillus cereus and a formate dehydrogenase from Candida boidinii, it is further advantageous that there is no need for the addition of external cofactor. The desired product is formed with high conversion and an enantiomeric purity of > 99% ee.