LAUSR

Abstract Low permeability of microbial cells and mass transfer limitations are major problems for efficient whole-cell biocatalysis. In this work, a method for enhanced enantioselective synthesis of S-EHPP, an intermediate for antidepressant drug fluoxetine via Kluyveromyces lactis whole-cell-catalyzed reduction of ethyl benzoyl acetate (EBA) was developed by the integration of cell permeabilization and medium engineering. Intracellular EBA reductase of K. lactis was found to be growth associated enzyme and 3-day grown cells that showed the highest activity, were permeabilized by pretreating them with different permeabilizing agents. Among the permeabilizing agents tested, acetone was the most effective and improved the whole-cell activity by 1.7-fold. The medium engineering by the addition of isopropyl alcohol (IPA) further enhanced the reaction rate through increasing mass transfer. Therefore, the integration of cell permeabilization with acetone and medium engineering with IPA, enhanced the activity of whole-cells by 2.0-fold while maintaining S-EHPP enantiomeric excess (EE) of >99.5%. This integration approach led to a S-EHPP yield of 86% within 13 h while only a 70% yield was achieved after 24 h by using untreated cells in IPA free reaction medium. These results demonstrated that the developed method could be applied to improve the performance of other whole-cell biocatalysts.