Tuning the enantioselectivity of secondary alcohol dehydrogenase from Thermoanaerobacter ethanolicus to accomplish a one-pot deracemization of alcohols

Deracemization, which involves conversion of racemic mixtures to their enantiopure forms, is an attractive approach to prepare optically active compounds such as alcohols and amines. The main objective of the research described in this proposal is to tune the enantioselectivity of secondary alcohol dehydrogenase from Thermoanaerobacter ethanolicus (TeSADH) to accomplish an efficient method of deracemization of secondary alcohols in one pot and one-step. A single enzymatic deracemization strategy was recently reported by Dr. Musa (the PI of the proposed project, ChemCatChem, 2016, 8, 14591463) and coworkers by controlling the enantioselectivities of the oxidation and reduction reactions catalyzed by W110A and W110G mutants of TeSADH. That work was highlighted on the cover page of the journal, which reflects the importance of this topic. However, the enantiomeric excesses of the optically active alcohols obtained by this method were not satisfactory. Herein, we propose the use of more than one mutant of TeSADH that exhibit different extent of enantioselectivities. The two mutants of TeSADH will be selected to have similar substrate scope, but different enantioselectivities. Moreover, the coenzyme recycling will be tuned to develop orthogonal recycling methods for the oxidation and reduction reactions, and thus try to accomplish a one pot deracemization of alcohols in one-step. The success of this deracemization will provide a sustainable biocatalytic approach to producing enantiopure alcohols from their racemates in high yields and enantioselectivities, which is of interest to pharmaceutical companies. The proposed method is not only environmentally benign but also superior to other deracemization approaches, such as dynamic kinetic resolution, in which a combination of two compatible catalysts is required. This project will help in training of the team members in important fields of biotechnology, and will result in publications in highly reputable journals in the field of catalysis.