Coevolution of the Activity and Thermostability of an ϵ‐Keto Ester Reductase for Better Synthesis of an (R)‐α‐Lipoic Acid Precursor

Abstract In this work, we have identified a significantly improved variant (S131Y/Q252I) of the natural ϵ‐keto ester reductase Cp AR2 from Candida parapsilosis for efficiently manufacturing ( R )‐8‐chloro‐6‐hydroxyoctanoic acid [( R )‐ECHO] through co‐evolution of activity and thermostability. The activity of the variant Cp AR2 S131Y/Q252I towards the ϵ‐keto ester ethyl 8‐chloro‐6‐oxooctanoate was improved to 214 U mg −1 —from 120 U mg −1 in the case of the wild‐type enzyme ( Cp AR2 WT )—and the half‐deactivating temperature ( T 50 , for 15 min incubation) was simultaneously increased by 2.3 °C in relation to that of Cp AR2 WT . Consequently, only 2 g L −1 of lyophilized E . coli cells harboring Cp AR2 S131Y/Q252I and a glucose dehydrogenase (GDH) were required in order to achieve productivity similar to that obtained in our previous work, under optimized reaction conditions (530 g L −1 d −1 ). This result demonstrated a more economical and efficient process for the production of the key ( R )‐α‐lipoic acid intermediate ethyl 8‐chloro‐6‐oxooctanoate.