Integration of natural deep-eutectic solvent and surfactant for efficient synthesis of chiral aromatic alcohol mediated by Cyberlindnera saturnus whole cells

Abstract

Efficiency of whole-cell biocatalysis in aqueous buffer solution is mainly limited by the low cellular membrane permeability and poor solubility of hydrophobic non-natural substrate. In this study, highly efficient bioreduction of 3,5-bis(trifluoromethyl)acetophenone (BTAP) to (S)-1-[3,5-bis(trifluoromethyl)phenyl]ethanol ((S)-BTPE) with excellent enantioselectivity (> 99.9 % ee) by a novel yeast isolate Cyberlindnera saturnus ZJPH1807 was achieved via a integrated strategy of natural deep-eutectic solvent (NADES) and surfactant. The introduction of L-carnitine: lysine (C:Lys, molar ratio 1:2) in the reaction medium improved cell membrane permeability effectively and relieved BTAP toxicity to the cells. The Tween-80 addition further accelerated catalytic yield by increasing solubility of BTAP for 7.6-fold compared with neat aqueous buffer solution. After the optimization of key reaction parameters, a 81.0 % yield within 24 h under 500 mM substrate loading was achieved in the established C:Lys/Tween-80-containing system, compared with a 76.4 % yield for 30 h in aqueous buffer system under 200 mM BTAP concentration. This biocatalytic process was also feasible at 500 mL preparation scale with a 79.7 % (S)-BTPE yield under 500 mM BTAP. The developed combinational strategy of NADES with surfactant is an effective approach for enhancing bioreductive efficiency of hydrophobic substrates mediated by whole-cell catalyst, and has great potential in biocatalysis.