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Product recovery of an enzymatically synthesized (−)-menthol ester in a deep eutectic solvent


Deep eutectic solvents (DESs) have gained increased attention as alternative reaction media for biocatalysis in recent years. There are many investigations on biotransformations in a variety of DESs, but the purification of bioproducts from DES reaction mixtures has not yet been sufficiently addressed. The present study demonstrates a product recovery strategy from a DES reaction medium composed of (−)-menthol and dodecanoic acid. Since the DES is not formed by equimolar amounts of the substrates, but the eutectic point occurs at a 3:1 molar ratio, product isolation is an important task for effective biocatalytic process development, even if the limiting substrate is converted completely. Both DES compounds acted as substrates and reaction solvent in the lipase-catalyzed esterification to synthesize (−)-menthyl dodecanoate. The product (−)-menthyl dodecanoate ester was separated from the DES reaction mixture by a vacuum distillation step and a second esterification reaction can be performed with the recovered (−)-menthol.

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The financial support by the German Ministry of Education and Research (BMBF) for the project “NIESEL—Niedrig schmelzende eutektische Solventien als Lösungsmittel für die Biokatalyse” (Grant no. 031B0014C) is gratefully acknowledged. The authors thank Florian Rudroff and Marko D. Mihovilovic (Institute of Applied Synthetic Chemistry, Vienna University of Technology) for the synthesis of the (−)-menthol dodecanoic acid ester.

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Correspondence to Dirk Holtmann.

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Pätzold, M., Burek, B.O., Liese, A. et al. Product recovery of an enzymatically synthesized (−)-menthol ester in a deep eutectic solvent. Bioprocess Biosyst Eng 42, 1385–1389 (2019). https://doi.org/10.1007/s00449-019-02125-6

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  • Deep eutectic solvent
  • Downstream processing
  • Lipase
  • Menthol
  • Vacuum distillation