Integration of biocatalysis and simulated moving bed technology constitutes an attractive option to overcome a broad set of constraints frequently encountered in enantioselective catalysis such as thermodynamic limitations, compromised reaction yields by long reaction times, product inhibition and product instability (Fig. 1). Another attractive variant of such a process concept is the integrated operation of mild enzymatic racemisation and chiral simulated moving bed technology (SMB) for the transformation of racemates into single enantiomers in 100% yield [1].

In this work we present the development, implementation and optimization of two hybrid processes for the production of enantiopure amino acid: (i) Integration of asymmetric synthesis of L-allo-threonine from glycine and acetaldehyde catalyzed by an aldolase (reaction yield 40% at equimolar substrate conc.) and SMB separation of threonine and glycine based on an ion-exchanger. (ii) Integration of enzymatic racemisation catalyzed by an amino acid racemase and SMB enantioseparation of the racemic amino acid based on the Chirobiotic TAG column (Astec,Whippany, NJ, USA).

[1] M. Bechtold, S. Makart, M. Heinemann, S. Panke, J Biotechnol 124 (2006) 146.

Figure 1:By coupling a continuously operated bioreactor to an SMB that provides efficient separation of the substrate/product mixture of the reactor effluent and subsequent recycling of the substrate Ðtheoretically- 100% chemical yield can be achieved