Using ionic liquids in whole-cell biocatalysis for the nucleoside acylation

Hui Wang ,Meiyan Yang,Guanglei Zhao,Furao Lai,Xiaofeng Li,Yan Lian,Yao Ren

doi:10.1186/preaccept-2071959743130788

Abstract

BackgroundThe use of biocatalysts has become an increasingly attractive alternative to traditional chemical methods, due to the high selectivity, mild reaction conditions and environmentally-friendly processes in nonaqueous catalysis of nucleosids. However, the extensive use of organic solvents may generally suffer from sever drawbacks such as volatileness and toxicity to the environment and lower activity of the biocatalyst. Recently, ionic liquids are considered promising solvents for nonaqueous biocatalysis of polyhydroxyl compounds as ILs are environmental-friendly.ResultsIn this research, we developed new IL-containing reaction systems for synthesis of long chain nucleoside ester catalyzed by Pseudomonas fluorescens whole-cells. Various ILs exerted significant but different effects on the bio-reaction. And their effects were closely related with both the anions and cations of the ILs. Use of 10% [BMI][PF6]/THF gave high reaction efficiency of arabinocytosine laurate synthesis, in which the initial rate, product yield and 5′-regioselectivity reached 2.34 mmol/L·h, 81.1% and >99%, respectively. Furthermore, SEM analysis revealed that ILs can alter the cell surface morphology, improve the permeability of cell envelopes and thus facilitate the mass transfer of substrates to the active sites of cell-bound enzymes.ConclusionOur research demonstrated the potential of ILs as promising reaction medium for achieving highly efficient and regioselective whole-cell catalysis.

Highlights

The use of biocatalysts has become an increasingly attractive alternative to traditional chemical methods, due to the high selectivity, mild reaction conditions and environmentally-friendly processes in nonaqueous catalysis of nucleosids
No product was detected when the ionic liquids (ILs) containing halogen anions, namely [BMI][Br] or [BMI][Cl]. These results indicated that the IL with lower hydrophilicity might favor the whole-cell mediated acylation, since the hydrophilicity of the anions increases in the order of [halide ions]- > [BF4]- > [PF6]- [20]
The research demonstrated the highly regioselective synthesis of long-chain nucleoside ester can be achieved by using P. fluorescens whole-cells in IL-organic systems

Summary

Introduction

The use of biocatalysts has become an increasingly attractive alternative to traditional chemical methods, due to the high selectivity, mild reaction conditions and environmentally-friendly processes in nonaqueous catalysis of nucleosids. The extensive use of organic solvents may generally suffer from sever drawbacks such as volatileness and toxicity to the environment and lower activity of the biocatalyst. The use of biocatalysts has become an increasingly attractive alternative to traditional chemical methods, due to the high selectivity, mild reaction conditions and environmentally-friendly processes [1,2]. Biocatalytic processes can be performed by using isolated enzymes or whole-cells. Whole-cell biocatalysts utilize the cellbound enzymes as well as intracellular enzymes which are biosynthesized during cell growth. The cooperation of a serial of different kinds of cell-bound enzymes and/ or intracellular enzymes forms an efficient whole-cell catalyst.

Methods

Results

Discussion

Conclusion