Assessment of process configurations to combine enantioselective chromatography with enzymatic racemization
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Assessment of process configurations to combine enantioselective chromatography with enzymatic racemization Isabel Harriehausen1 · Katarzyna Wrzosek1 · Heike Lorenz1 · Andreas Seidel‑Morgenstern1 Received: 8 October 2019 / Revised: 31 March 2020 / Accepted: 3 April 2020 © The Author(s) 2020
Abstract Enantioselective chromatography is nowadays a reliable tool for single enantiomer production from a racemate. The recovery of the distomer by racemization and recycling is a promising method to tackle the 50% yield constraint and to increase the productivity. In this paper three process configurations are compared. The production of enantiopure mandelic acid and methionine enantiomers exploiting different enzymes for racemization are evaluated as part of different chromatographic process configurations. First, the benefits of conventional simulated moving bed (SMB) chromatography in contrast to a single column batch separation unit are assessed in integrated configurations. Then, a concept of coupling the racemization with a simpler three-zone SMB unit, where one regeneration zone is removed, is evaluated. Keywords Chiral separation · Batch chromatography · SMB processes · Enzymatic racemization · Distomer recovery · Process integration
1 Introduction For the provision of pharmaceutical ingredients or in the food and agrochemical industries, the production of pure enantiomers is crucial. Even though chiral synthesis by fermentation is well established, e.g. for production of the essential amino acids, this pathway is not always available or requires a long reaction chain. In these cases, the racemic approach of an unselective synthesis with a subsequent separation and recycling of the distomer is becoming an attractive alternative (Francotte 2001). The separation can be done e.g. by enantioselective chromatography or preferential crystallization (Lorenz and Seidel-Morgenstern 2014). For enantioselective chromatography there are versatile and highly selective but costly chiral stationary phases available (Franco et al. 2001). A desirable exploitation of the distomer after separation can be done in connection with racemization. Such reactions can be realized under extreme pH or temperature conditions and/or catalyzed chemically or enzymatically (MartínMatute and Bäckvall 2007). Besides enhancing the reaction * Isabel Harriehausen harriehausen@mpi‑magdeburg.mpg.de 1
Max-Planck-Institut fur Dynamik komplexer technischer Systeme, Sandtorstr. 1, 39106 Magdeburg, Germany
rate, enzymatic racemization allows the operation under mild process conditions. Despite their large potential, the amount of available racemases is still limited (Würges et al. 2009; Radkov and Moe 2013; Femmer et al. 2016). When immobilized on a resin and packed in a fixed bed reactor, enzymes can show high stability and no extra enzyme recovery step is needed (Wrzosek et al. 2018). Since the driving force for racemization is the enantiomeric excess and concentration of the distomer, for optimal process performance the enzymatic reactor can be positi
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