We report a new method for developing a deep eutectic solvent (DES) and its application as a cosolvent in biocatalytic reactions. A novel oligopeptide-based DES containing choline chloride (ChCl) and glutathione (GSH, comprised of Glu, Cys, and Gly) was designed and synthesized. Using this oligopeptide-based DES as a cosolvent, we achieved efficient asymmetric reduction of 3,5-bis(trifluoromethyl) acetophenone catalyzed by Trichoderma asperellum ZJPH0810. Under optimized conditions, the substrate loading increased 2-fold in the ChCl/GSH-containing system compared with that in aqueous buffer (100 vs 50 mM), with a yield >90% and enantiomeric excess value >99%. To broaden the application of the established ChCl/ GSH-containing system in biocatalysis, the asymmetric reductions of different substrates in developed reaction medium were further investigated. Compared with the aqueous system, the ChCl/GSH-containing system enhanced substrate loading (50 vs 100 mM when catalyzed by Candida tropicalis 104), obviously improved the yield (i.e., from 70.4 to 87.6% when catalyzed by C. tropicalis 104, from 65.9 to 83.8% by Candida parapsilosis ZJPH1305), and shortened the reaction time greatly (30 vs 24 h when catalyzed by C. tropicalis 104, or 1.5 vs 1.0 h by recombinant Escherichia coli). These findings provide valuable insight for the design of task-specific and sustainable oligopeptide-based DESs for biocatalysis.

BACKGROUND Deep eutectic solvents (DESs) derived from bio‐available materials are promising eco‐friendly solvents in the field of biocatalysis. However, the type of bio‐based DES is still limited and its application in bioprocess has not been well‐explored. We adopted a design strategy via the combination of choline and amino acids to synthesize novel bio‐based DESs, aimed to enhance biocatalytic efficacy by exploiting the developed DESs as co‐solvents. RESULTS Various bio‐based DESs were synthesized, where the two components are both bio‐available (choline and amino acids). Their performances in the bioreduction of 2‐chloro‐1‐(3,4‐difluorophenyl)ethanone (CFPO) were subsequently evaluated with recombinant Escherichia coli cells. The efficient asymmetric production of (S)‐2‐chloro‐1‐(3,4‐difluorophenyl)ethanol ((S)‐CFPL) was successfully achieved in a developed choline acetate/lysine (ChAc/Lys)‐containing medium. ChAc/Lys can strengthen coenzyme regeneration and properly improve cell membrane permeability during bioreduction, which account for high conversion. After optimized reaction parameters were conducted in the ChAc/Lys‐buffer system, 87.0% (S)‐CFPL yield was observed with > 99.9% enantiomeric excess (ee) value at 1 mol L−1 CFPO content. The substrate loading in the established ChAc/Lys‐buffer system was increased by 3.3‐fold compared to aqueous medium. This bioprocess was also proved to be feasible at 500 mL preparative‐scale with a satisfactory conversion. CONCLUSION ChAc/Lys bio‐DES is a promising and biocompatible co‐solvent. Introducing ChAc/Lys to the reaction system is an effective strategy for challenging high substrate loading for bioreduction. Our results give a valuable insight for developing green and benign sustainable bio‐DESs for biotransformation. © 2020 Society of Chemical Industry

(R)-2-Chloro-1-(2,4-dichlorophenyl) ethanol is a chiral intermediate of the antifungal agent Miconazole. A bacterial strain, ZJPH1806, capable of the biocatalysis of 2-chloro-1-(2,4-dichlorophenyl) ethanone, to (R)-2-chloro-1-(2,4-dichlorophenyl) ethanol with highly stereoselectivity was isolated from a soil sample. It was identified as the Acinetobacter sp., according to its morphological observation, physiological-biochemical identification, and 16S rDNA sequence analysis. After optimizing the key reaction conditions, it was demonstrated that the bioreduction of 2-chloro-1-(2,4-dichlorophenyl) ethanone was effectively transformed at relatively high conversion temperatures, along with glycerol as cosubstrate in coenzyme regeneration. The asymmetric reduction of the substrate had reached 83.2% yield with an enantiomeric excess (ee) of greater than 99.9% at 2 g/L of 2-chloro-1-(2,4-dichlorophenyl) ethanone; the reaction was conducted at 40 °C for 26 h using resting cells of the Acinetobacter sp. ZJPH1806 as the biocatalyst. The yield had increased by nearly 2.9-fold (from 28.6% to 83.2%). In the present study, a simple and novel whole-cell-mediated biocatalytic route was applied for the highly enantioselective synthesis of (R)-2-chloro-1-(2,4-dichlorophenyl) ethanol, which allowed the production of a valuable chiral intermediate method to be transformed into a versatile tool for drug synthesis.