Negative effect of [bmim][PF 6 ] on the catalytic activity of alcohol dehydrogenase: mechanism and prevention

BACKGROUND: [bmim][PF 6 ] is a hydrophobic ionic liquid which could be considered as an environmentally friendly solvent for biocatalysis. In pure [bmim][PF 6 ], however, alcohol dehydrogenase from yeast (YADH) has no catalytic activity. The aim of the present work was (1) to quantitatively study the negative effect of [bmim][PF 6 ] on the catalytic activity of YADH and the related mechanism and (2) to made an attempt to lessen the negative effect of [bmim][PF 6 ] on YADH by microemulsifying [bmim][PF 6 ]. RESULTS: The activity of YADH in the homogeneous solution formed by H 2 O, CH 3 CH 2 OH and [bmim][PF 6 ] decreased rapidly with the increase of the molar fraction of [bmim][PF 6 ]. The inhibitory effect of [bmim][PF 6 ] on YADH was probably caused by the competition of the imidazole group of [bmim][PF 6 ] with the coenzyme NAD + for the binding sites on YADH. In a water‐in‐[bmim][PF 6 ] microemulsion, YADH was catalytically active due to the formation of the interfacial membrane of the nonionic surfactant TritonX‐100, which separated YADH from [bmim][PF 6 ] and avoided the direct inactivation of [bmim][PF 6 ] on YADH. Under optimal conditions, the activity of YADH was as high as 51 µmol L −1 min −1 . CONCLUSION: [bmim][PF 6 ] was an inhibitor of YADH and its negative effect on YADH could be lessened by its microemulsification. Copyright © 2008 Society of Chemical Industry