A successful process to extract lipolytic enzymes based on an aqueous biphasic system (ABS), which uses both ionic liquids (ILs) and a high charge-density inorganic salt (K 2 CO 3 ), is proposed in this work. The activity of a model Thermomyces lanuginosus lipase (TlL) in some of the most common hydrophilic ILs, based on the 1-alkyl-3-methylimidazolium cation, combined with chloride, alkylsulfate, alkylsulfonate and acetate, was investigated. Several operating conditions influencing lipase activity and ABS formation were investigated. Parameters such as temperature, pH, deactivation kinetics and water content were evaluated in order to propose a viable extraction process. A deeper analysis in terms of enzyme deactivation kinetics was carried out, and the data were modelled through a series-type deactivation equation. ATR-FTIR studies aimed at identifying the TlL structure in selected ILs have also provided an insight into the enzyme deactivation behaviour.

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: Three enzymes (lysozyme, EC 3.2.1.17 ; a-chymotrypsin, EC 3.4.21.1 ; and Candida rugosa lipase, EC 3.1.1.3) have been modiüed in order to alter their surface hydrophobic/hydrophilic balance in opposite directions, by chemoenzymatic glycosylation and chemical binding of polyethylene glycol (PEG). The thermal stability in aqueous environment of the produced biocatalysts was studied, and two diþ erent approaches were considered : the determination of half-life times and the mechanistic analysis of the deactivation kinetics. The comparison of half-life times indicated that an increase in enzyme surface hydrophobic character induced a remarkable amelioration in thermostability, while the increase in hydrophilic character produced the opposite eþ ect. However, the investigation of kinetic and thermodynamic parameters of enzyme deactivation revealed, in some cases, secondary stabilisation eþ ects during some step of the mechanism, which would not have been detected if only half-life times had been considered.1999 Society of Chemical Industry (

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