Activation of Lipase by an Ionic Liquid

Lozano and co-workers reported an interesting stabilization effect of IL for lipase-catalyzed reaction the authors discovered that the presence of an appropriate substrate was essential for stabilization of enzyme in an IL solvent. The half lifetime of native CAL was only 3.2 h in [emim][PFg] solvent, while it lengthened remarkably to 7500 h in the presence of the substrate. The authors succeeded in demonstrating an efficient lipase-recyclable use system based on SCCO2 solvent (Fig. 9). -  

In the reaction, it was essential to use an IL as a co-solvent. Lozano, Iborra and co-workers recently reported an interesting stabilizing effect of two types of water-immiscible ILs ([emim][TFSI] and [BuMe3N][TFSI]) for CAL-B-catalyzed transesterification of vinyl butyrate. The synthetic activity and the stability of the enzyme in these IL solvent systems were markedly enhanced as compared to those in hexane. CAL-B maintained its activity higher than 75% after 4 days of incubation in [emim][TFSI] solvent, while it showed an activity of only 25% when incubated in both water and hexane media at 50°C. Comparison of the ratio of a-helix and (3-sheet by CD spectra showed the activity was closely related with a-helix content which reduced to 31% immediately after lipase was added to hexane and had reached only 2% after 4 days in hexane. On the contrary, no significant reduction of a-helix content was 

A mixed solvent system of an IL with organic solvent sometimes gave very nice results LundelP reported that enhanced enantioselectivity was obtained when lipase-catalyzed acylation was carried out in a mixed solvent system of [emim][TFSI] with t-BuOMe (1 1), while poor enantioselectivity was recorded for that in the pure [emim][TFSI] solvent (Fig. 11). 

Ganske and co-workers reported that lipase-catalyzed acylation of a glucose derivative proceeded smoothiy in a mixed soivent of [bmim][BF4] with r-BuOH, while no reaction took place in [bmim][BF4] (Fig. 12). These results taught us that a mixed soivent system of IL with organic solvent may be a good solution if the desired reaction did not take piace in a pure IL solvent. 

Modified enantioselectivity was reported if the reaction was carried out in an IL solvent instead of traditional organic soivent. For instance, Kaziauskas and Kim independently reported that the regioselectivity of lipase-catalyzed reaction was enhanced if the reaction was carried out in an IL solvent system (Fig. 13). Recently Wu and co-workers reported another chip of iipase-catalyzed reaction a 

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