Biocatalysis Of13-ethyl-gon-4-en-3,17-dione In A Ionic Liquid/Water Biphasic System

Biphasic biocatalytic processes are usually applied in whole-cell biotransformation to overcome the low water solubility of substrates as well as their inhibitory effects on the biocatalyst. However, most of organic solvents used as the second phase frequently have negative effects on catalytic activity of microbial cells. Ionic liquids (ILs) have recently been recommended as attractive alternatives to organic solvents for biocatalyst in biphasic process, as they are environment friendly and high partition coefficient. Based on the model that15a-Hydroxylation of13-ethyl-gon-4-en-3,17-dione can be produced by Penicillium raistrickii ATCC10490, this study sought to determine the biocompatibility of four ILs on P. raistrickii and evaluate their applicability in the IL/water biphasic system for15a hydroxylation of13-ethyl-gon-4-en-3,17-dione by P. raistrickii.Three assays, such as survival rate of spores, oxford-cup test and uptake of glucose, were performed for assessing the biocompatibility of ILs with filamentous fungi. The results indicated that the uptake of substrate could be the most suitabe method to identify the biocompatible ionic liquids. The toxicity of ILs on P. raistrickii was in the following order:[HMIm][NTf2]>[HMIm][PF6]>[BMIm][PF6][BMIm][NTf2].In this work, four kinds of water-immiscible ILs were evaluated with respect to their applicability in biphasic steroid biotransformation. The result indicated that, the IL/water biphasic system used [BMIm][NTf2] as the second liquid phase tested enhanced15a-hydroxylation efficiency mostly compared to that in a pure aqueous system. In addition, the effects of buffer pH, VIL/VAq, substrate concentration and cell density on steroid bioconversion were also investigated. It was found that, the use of [BMIm][NTf2] and [BMIm][PF6] as the second liquid phase for15a hydroxylation of13-ethyl-gon-4-en-3,17-dione resulted in a product conversion of70.21%and61.37%.After several extractions, the ILs were recovered. Then four recycles of reuse of the two ILs in biotransformation were carried out by P. raistrickii and the results indicated that the product conversion using reused [BMIm][NTf2] and [BMIm][PF6] was55.26%and50.13%respectively. The above results suggest the potential industrial application of ILs-based biphasic systems for steroid biotransformation.