title: Ionic liquids as alternative co-solvents for laccase: study of enzyme activity and stability.
abstract: The activity and stability of commercial laccase (DeniLite base) in three different water soluble ionic liquids (ILs) (1-ethyl-3-methylimidazolium 2-(2-methoxyethoxy) ethylsulfate, [emim][[MDEGSO4], 1-ethyl-3-methylimidazolium ethylsulfate, [emim][EtSO4], and 1-ethyl-3-methylimidazolium methanesulfonate, [emim][MeSO3]) have been studied and compared to that in two organic solvents (acetonitrile and dimethyl sulfoxide). Initial enzyme activities were similar among the ILs if the same conditions were used. A high reduction on initial enzyme activity was found with acidic pH (5.0). The effect of pH and solvent concentration on enzyme stability were investigated in more detail for 1 week. The enzyme maintained a high stability at pH 9.0 for all ILs tested. [emim][MDEGSO4] was the most promising IL for laccase with an activity loss of about 10% after 7 days of incubation. The kinetic studies in the presence of ABTS as substrate allowed to calculate the Michaelis- Menten parameters. Good agreement was found between experimental data and calculated values using the Michaelis-Menten mechanism, with a total average relative deviation of 2.1%.
authors.affiliation: Laboratory of Separation and Reaction Engineering (LSRE), Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto, Rua do Dr. Roberto Frias, 4200-465, Porto, Portugal.
authors.forename: Ana Paula Mora
authors.initials: AP
authors.lastname: Tavares
authors.forename: Oscar
authors.initials: O
authors.lastname: Rodriguez
authors.forename: Eugénia A
authors.initials: EA
authors.lastname: Macedo
mesh_terms: D003198:Computer Simulation; D004789:Enzyme Activation; D004795:Enzyme Stability; D052578:Ionic Liquids / Q000737:chemistry*; D007700:Kinetics; D042845:Laccase / Q000737:chemistry*; D008956:Models, Chemical; D012997:Solvents / Q000737:chemistry*
chemical_list: D052578:Ionic Liquids; D012997:Solvents; D042845:Laccase