Efficient Asymmetric Reduction of 4-(Trimethylsilyl)-3-Butyn-2-One by Candida parapsilosis Cells in an Ionic Liquid-Containing System

Abstract

Hydrophilic ionic liquids (ILs) were employed as green solvents to construct an IL-containing co-solvent system for improving the asymmetric reduction of 4-(trimethylsilyl)-3-butyn-2-one by immobilized Candida parapsilosis cells. Among 14 hydrophilic ILs examined, 1-(2′-hydroxyl)ethyl-3-methylimidazolium nitrate (C2OHMIM·NO3) was considered as the most suitable IL for the bioreduction with the fastest initial reaction rate, the highest yield and the highest product e.e., which may be due to the good biocompatibility with the cells. For a better understanding of the bioreduction performed in the C2OHMIM·NO3-containing co-solvent system, the effects of several crucial variables were systematically investigated. The optimal C2OHMIM·NO3 content, substrate concentration, buffer pH, co-substrate concentration and temperature were 10% (v/v), 3.0 mmol/L, 5.0, 98.1 mmol/L and 30°C, respectively. Under the optimal conditions, the initial reaction rate, the maximum yield and the product e.e. were 17.3 µmol/h gcell, 95.2% and >99.9%, respectively, which are much better than the corresponding results previously reported. Moreover, the immobilized cells remained more than 83% of their initial activity even after being used repeatedly for 10 batches in the C2OHMIM·NO3-containing system, exhibiting excellent operational stability.

Regio- and enantioselective microbial hydroxylation and evaluation of cytotoxic activity of β-cyclocitral-derived halolactones

“…The most popular biocatalytic process used to obtain the optically active alcohols is asymmetric reduction of prochiral ketones [ 25 – 27 ] and lipase-catalyzed kinetic resolution of racemic alcohols [ 28 , 29 ]. In both cases the basic limitation is the presence of carbonyl or hydroxy function already in the defined place in a substrate molecule.…”

Whole-Cell Biocatalytic Processes with Ionic Liquids

“…The reason might be that the hydroxyl-functionalized IL [EOHMIm]­[NO 3 ] and water can form an OH-bridged protic environment that is favorable to the activity of the biocatalysts. BF 4 – - and Cl – -based ILs (at 10 and 23% v/v, respectively) showed low biocompatibility and caused significant decrease in cell viability, leading to the loss of the catalytic activity. , However, it cannot simply be concluded that BF 4 – or Cl – is more toxic toward the cells because different kinds of IL used, IL content­(v/v), the property of substrate and product, the time of exposure, the indicator microorganisms used and even different biomass concentrations may substantially influence the cell survival and metabolism. There is a pressing need for additional systematic studies on the combined effects of these factors on cell viability in order to facilitate industrial applications of ILs.…”