Donor Amine Salt-Based Continuous in situ-Product Crystallization in Amine Transaminase-Catalyzed Reactions

The unfavorable reaction equilibrium of transaminase-catalyzed reactions is a major challenge for the efficient biocatalytic synthesis of chiral amines. In this study the synthetic utilization of a salt-based, continuous in situ-product crystallization is described to overcome the thermodynamic limit in amine transaminase-reactions using only the commonly used amine donor isopropylamine. The simultaneous dissolution of isopropylammonium 3,3-diphenylpropionate (donor salt) in combination with the crystallization of the product salt facilitates a thermodynamic shift of the continuous amine transaminase-catalyzed reaction. The main process necessity is a lower product salt solubility in comparison to the applied donor salt. This concept facilitates a stoichiometric use of isopropylamine in combination with a significantly lowered concentration of the amines in solution.