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ARTICLE This journal isAqueous two-phase systems (ATPS) are efficient, environmentally friendly, and "biocompatible" separation processes, which allow the recovery of enzymes. The most common systems are based on polymers and salts, and recently, to overcome the low polarity difference between the phases of the polymeric systems, ATPS based on ionic liquids (ILs) were proposed and have been successfully applied on the field. This work discusses the use of imidazolium-based ILs not as phase forming compounds but as adjuvants (5 wt%) in ATPS of polyethylene glycol systems (1500, 4000, 6000 and 8000 g.mol -1 ) with potassium phosphate buffer at pH 7, in the extraction and purification of a lipase produced by submerged fermentation by Bacillus sp. ITP-001. An initial optimization study was carried with the commercial lipase B from Candida antarctica (CaLB) allowing to further purify the commercial CaLB (Purification Factor = 5.2). Using the optimized conditions, a Purification Factor of 245 for the lipase from Bacillus sp. ITP-001 was achieved with 1-hexyl-3-methyl imidazolium chloride. The high purification factor is a consequence of the favorable interactions between the IL and the contaminant proteins that migrate for the PEG-rich phase, where the IL also concentrates preferentially, while the enzyme remains in the saltrich phase.

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Candida rugosa lipase was immobilized by covalent binding on controlled pore silica (CPS) using glutaraldehyde as cross-linking agent under aqueous and nonaqueous conditions. The immobilized C. rugosa was more active when the coupling procedure was performed in the presence of a nonpolar solvent, hexane. Similar optima pH (7.5-8.0) was found for both free and immobilized lipase. The optimum temperature for the immobilized lipase was about 10 degrees C higher than that for the free lipase. The thermal stability of the CPS lipase was also greater than the original lipase preparation. Studies on the operational stability of CPS lipase revealed good potential for recycling under aqueous (olive-oil hydrolysis) and nonaqueous (butyl butyrate synthesis) conditions.