Effect Of Ionic Liouid On The Biotransformation Of Steroids 1-en-dehydrygenaion

Prednisone acetate(PA),an important anti-inflammatory and anti-allergy steroid,was mainly produced by △ 1,2-dehydrogeneration of cortisone acetate(CA)using Arthrobacter simplex.However,the poor solubility of steroids in aqueous media seriously limits the productivity of the CA biotransformation system.To improve the conversion rate of CA,the ionic liquid being green and sustainable solvents currently attracting widespread academic and industrial interest,were investigated.The focus of this work is to investigate the effects of the ionic liquids on the growth and integrity of A.simplex,the solubility of PA,as well as the bioconversion rate of steroid dehydrogenation.Toxicity of various ionic liquids to A.simplex was investigated by the glucose uptake assay and the viability test kit.Results indicated that the new class of ionic liquids(namely,deep eutectic solvents,DESs)was more biocompatible with A.simplex cell compared to the traditional ionic liquids.Among the three DESs used in this study,ChCl:Gly was better in terms of biocmpatibility than ChCl:U and ChCl:EG.Substrate Solubility in DESs is important with regard to the initial substrate feeding concentration,which determines process efficiency.The enhanced solubility of CA in DESs in comparison with aqueous water in the order of ChCl:Gly<ChCl:EG<ChCl:U was observed.The effect of DESs on △1,2-dehydrogeneration of CA to PA by resting A.simplex cells was also investigated.The use of traditional ionic liquids for CA biotransformation showed the much lower conversion rate(<5%)when the substrate concenetration is 4%.On the other hand,ChCl:U resulted in drastically improved yield of CA 85%and 90%,respectively,by both free and immobilized A.simplex cells with 4%substrate concentration.Of the three water-miscible DESs tested,ChCl:U showed slightly better performance.Thus,ChCl:U was chosen as a co-solvent for further investigation on biodehydrogeneration of cortisone acetate(CA)using immobilized A.simplex cells.For substrate feeding concentration of 50 g/L,the conversion reached up to 97.14%by immobilized A.simplex cells(4 gDW/L)in the 6%ChCl:U containing system for 60 h.The reusability of recycled immobilized A.simplex and DES in biodehydrogenation of steroid was also evaluated.The immobilized cells in DESs mixture appeared to be more stable than that in the pure aqueous system.After 5 cycles,the bioconversion of substrate still reached more than 80%.