Effect of ionic liquids, organic solvents and supercritical CO2 pretreatment on the conformation and catalytic properties of Candida rugosa lipase

The objective of this work is to assess the structure and activity of Candida rugosa lipase (CRL) pretreated with seventeen ionic liquids (ILs), five organic solvents and super-critical carbon dioxide (SC-CO2). The results revealed that anion selection of ILs showed generally much greater effects on CRL esterification activity than cation choice, and CRL pretreated by ILs with strong water miscible properties showed very low esterification activity. The highest CRL activity treated with ILs [Hmim][PF6] was obtained with the value of 45078.0 U/g-protein. Furthermore, the CRL activities pretreated with five conventional organic solvents were also examined and the values increased with the log P decrease of organic solvents when log P was lower than 2.0. Finally, the CRL activities were respectively 1.2- and 1.3-fold higher over the untreated ones after pretreatment with sub- and super-critical CO2 under the pressures of 6 MPa and 15 MPa at 40 °C for 20 min. Further analyses via FT-IR demonstrated that the high activity of CRL pretreated with ILs, organic solvents and SC-CO2 was probably caused by the changes of CRL secondary structure. In conclusion, the results in this work will be helpful for us to choose the suitable reaction medium in CRL biocatalysis and biotransformation reactions.

The effect of cation and anion structure of ILs on CRL7 activity.Figure optionsDownload as PowerPoint slideHighlights
► We assessed the conformation and activity of CRL7 in seventeen ionic liquids.
► We examined the effect of organic solvents on conformation and activity of CRL.
► The influence of SC-CO2 on structure and activity of CRL7 was also studied.
► Overall, CRL7 activity in ILs was higher than in organic solvents and SC-CO2.
► CRL7 activity variance depended on changes in α-helix content of secondary structure.