Development of dynamic kinetic resolution processes for biocatalytic production of natural and nonnatural L-amino acids

Two different dynamic kinetic resolution processes for the production of a number of natural and nonnatural L-amino acids at 100% chemical and optical yield have recently been established at Degussa. The first process is based on the dynamic kinetic resolution of 5-monosubstituted hydantoins using tailor-made whole-cell biocatalysts coexpressing a L-carbamoylase, a hydantoin racemase, and a hydantoinase. The hydantoin-converting pathway was optimized by adjusting expression levels of the respective enzymes as well as by inverting the enantioselectivity of the D-selective hydantoinase. This resulted overall in a 50-fold improved productivity and significant reduction of biocatalyst cost. The second process is based on the dynamic kinetic resolution of N-acetyl amino acids using an acylase in combination with a novel racemase from Amycolatopsis orientalis subsp. lurida. This racemase could overcome the problem of substrate inhibition and requirement of high concentrations of divalent metal ions which limits the use of other N-acylamino acid racemases described in the literature.