Performance of Recombinant‐Whole‐Cell‐Catalyzed Reductions in Deep‐Eutectic‐Solvent–Aqueous‐Media Mixtures

Abstract

Deep‐eutectic solvents (DES) are cost‐effective, nonhazardous solvents that may be used in biocatalysis as nonconventional media that enable biotransformations with industrially sound high substrate loadings. Based on promising prognoses, this paper explores successfully the use of whole cells overexpressing oxidoreductases as biocatalysts for the stereoselective reduction of ketones in different DES–aqueous‐media solutions. Enzymes like Ralstonia sp. alcohol dehydrogenase (ADH) and horse liver ADH, overexpressed in Escherichia coli, remain active at different DES proportions (for example, DES:buffer, 80:20 v/v) to enable nonconventional biotransformations. Furthermore, the enantiomeric excesses obtained for a broad range of aromatic substrates increase significantly if DES is added, which provides a useful tool for combining high substrate loadings and improved enzymatic selectivities while working with nonhazardous solvents. Different DES are successfully employed, which gives hints of the potential that these emerging solvents may have.

Deep Eutectic Solvents: The Organic Reaction Medium of the Century

“…In addition, recombinant whole cells overexpressing oxidoreductases have been employed as biocatalysts for the stereoselective reduction of alkyl phenyl ketones in different DES (ChCl-gly)-aqueous-media solutions, the enantiomeric excesses obtained being increased significantly if DES is present. [135] …”

Recent advances in whole cell biocatalysis techniques bridging from investigative to industrial scale

“…As a result, deep eutectic solvents (DESs) currently evolve as a more sustainable alternative granting similar advantages as ILs in comparison to classical organic solvents [39,40]. Compatibility of DESs with purified enzyme preparations has been demonstrated already for enzymes of different classes, but also recently for whole cell catalysts, such as wildtype Arthrobacter [41] or Acetobacter [42] species, baker's yeast [43,44], and recombinant E. coli [45].…”

Modeling Alcohol Dehydrogenase Catalysis in Deep Eutectic Solvent/Water Mixtures

“…A eutectic mixture of ChCl and glycerol (Gly) (1:2 mol mol −1 ), which is also known as glyceline, was selected as a prototypical DES for ADH‐catalyzed reactions. Glyceline is one of the most successfully applied DESs for biocatalysis . MD simulations focus on the quantitative analysis of protein flexibility and hydration level, whereby the results from enzymatic activity and stability are correlated and explained.…”