ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Protein-coated microcrystals of Prunus armeniaca hydroxynitrile lyase: an effective and recyclable biocatalyst for synthesis of (R)-mandelonitrile

Deniz Yildirim, Ali Toprak, Dilek Alagöz, and S. Seyhan Tukel

University of Cukurova, Adana, Turkey

E-mail: dyildirim@cu.edu.tr

Abstract: In this study, the crude solution of Prunus armeniaca hydroxynitrile lyase (ParsHNL) was simultaneously precipitated onto K₂SO₄ salt in acetone to immobilize ParsHNL as protein-coated microcrystals and the obtained preparations (PCMCs-ParsHNL) were used for the synthesis of (R)-mandelonitrile in buffer-saturated methyl tert-butyl ether (pH 4.0). The yield and enantiopurity of (R)-mandelonitrile were 100 and 90.5%, respectively, for free HNL, whereas the corresponding yield and enantiopurity values were 100 and 99.8%, respectively, for PCMCs-ParsHNL after 96 h reaction time. The free HNL and PCMCs-ParsHNL were stored at room temperature and 5 °C during 30 days and the results showed that PCMCs-ParsHNL had better storage stability compared to the free HNL at both room temperature and 5 °C. PCMCs-ParsHNL was imaged by a scanning electron microscopy and PCMCs-ParsHNL was rectangular in shape. PCMCs-ParsHNL was recycled five times in the synthesis of (R)-mandelonitrile and 75.2% initial activity recovery and 99.8% enantiomeric excess for (R)-mandelonitrile was determined after five uses. Thus, immobilizing ParsHNL as PCMCs provided highly active and reusable HNL preparations for (R)-mandelonitrile synthesis in buffer-saturated methyl tert-butyl ether.

Keywords: Hydroxynitrile lyase ; Protein-coated microcrystals ; Transcyanation ; Enantiopure ; Cyanohydrins 

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-018-0577-5

Chemical Papers 73 (1) 185–193 (2019)