Comparison of different chemoenzymatic process routes to enantiomerically pure amino acids

Abstract

Five common biocatalytic process platforms for the production of enantiomerically pure amino acids are compared along four different dimensions of merit: i) enantioselectivity, ii) overall yield, iii) biocatalyst operating stability, and iv) reactor space-time yield. All processes practiced on industrial scale utilize biocatalysts of very high enantioselectivity. Short efficient process routes are a necessity, giving an inherent advantage to routes based on lyase reactions or reduction of prochiral keto acids. For processes based on the splitting of a racemate, recycling the unwanted enantiomer is crucial. The pKa value of abstracting the α-proton serves as a first indication of the difficulty of achieving overall yields far in excess of 50% through dynamic resolution. High solubility of substrates and products was found to favor high reactor productivity (space-time-yield s.t.y. > 1 kg/(l-d)) and high biocatalyst productivity (enzyme consumption number e.c.n. < 500-1000 U/kg of product).