New Continuous Production Process for Enantiopure (2R,5R)-Hexanediol

A new continuous production process has been developed for optically active pure (2 R,5 R )-hexanediol. The process uses resting whole cells of Lactobacillus kefir DSM 20587 as a biocatalyst. The reduction of (2,5)-hexanedione to (2 R,5 R )-hexanediol was carried out in a 2-L continuously operated membrane reactor. Conversion of (2,5)-hexanedione was nearly quantitative and the selectivity between product and intermediate was 78% for the product. Enantioselectivity and diastereoselectivity were >99% for the whole period. The productivity of L. kefir could be increased by factor 30. (2 R,5 R )-Hexanediol was continuously produced over 5 days with a space−time yield of 64 g·L - 1 ·d - 1 .