Negative effect of [bmim][PF6] on the catalytic activity of alcohol dehydrogenase: mechanism and prevention

BACKGROUND: bmim]PF₆] is a hydrophobic ionic liquid which could be considered as an environmentally friendly solvent for biocatalysis. In pure bmim]PF₆], 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]PF₆] on the catalytic activity of YADH and the related mechanism and (2) to made an attempt to lessen the negative effect of bmim]PF₆] on YADH by microemulsifying bmim]PF₆]. RESULTS: The activity of YADH in the homogeneous solution formed by H₂O, CH₃CH₂OH and bmim]PF₆] decreased rapidly with the increase of the molar fraction of bmim]PF₆]. The inhibitory effect of bmim]PF₆] on YADH was probably caused by the competition of the imidazole group of bmim]PF₆] with the coenzyme NAD⁺ for the binding sites on YADH. In a water‐in‐bmim]PF₆] microemulsion, YADH was catalytically active due to the formation of the interfacial membrane of the nonionic surfactant TritonX‐100, which separated YADH from bmim]PF₆] and avoided the direct inactivation of bmim]PF₆] on YADH. Under optimal conditions, the activity of YADH was as high as 51 µmol L^?1 min^?1. CONCLUSION: bmim]PF₆] was an inhibitor of YADH and its negative effect on YADH could be lessened by its microemulsification. Copyright © 2008 Society of Chemical Industry