Abstract
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 waterβinβ[bmim][PF~6~] microemulsion, YADH was catalytically active due to the formation of the interfacial membrane of the nonionic surfactant TritonXβ100, 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 Β΅mol L^β1^ min^β1^.
CONCLUSION: [bmim][PF~6~] was an inhibitor of YADH and its negative effect on YADH could be lessened by its microemulsification. Copyright Β© 2008 Society of Chemical Industry