Ionic liquids for aqueous two‐phase extraction and stabilization of enzymes

Abstract

The ionic liquid (IL) Ammoeng110 contains cations with oligoethyleneglycol units and was found to be highly effective for the formation of aqueous two-phase systems (ATPS) that can be used for the biocompatible purification of active enzymes. Above critical concentrations of the IL and an inorganic salt in aqueous solution, phase separation takes place resulting in the formation of an IL-enriched upper and a salt-enriched lower phase. For the optimization of the composition of IL-based ATPS with regard to the extraction of catalytically active enzymes, the Box-Wilson method of experimental design was successfully applied; IL-based ATPS proved to be suitable for the purification and stabilization of two different alcohol dehydrogenases (from Lactobacillus brevis and a thermophilic bacterium). Both enzymes were enriched in the IL-containing upper phase resulting in an increase of specific activity by a factor of 2 and 4 respectively. Furthermore, the presence of IL within the system provided the opportunity to combine the extraction process with the performance of enzyme-catalyzed reactions. The IL was found to exhibit a stability improving effect on both enzymes and a solubility enhancing effect on hydrophobic substrates. Thus the conversion and volumetric productivity of ADH catalyzed reduction of acetophenone could be increased significantly.

Methods for stabilizing and activating enzymes in ionic liquids—a review

“…Xu and co-workers 183,185 utilized the conductorlike screening model for real solvents (COSMS-RS) to derive various parameters (such as misfit, H-bonding and van der Waals interaction energy) to understand the multiple interactions in ILs; the model also provides guidance in designing the structures of cations and anions. 190 The Kragl group 191 found that an IL in the Ammoeng family -Ammoeng 110 ( Fig. 5) -is quite effective in forming aqueous two-phase (ATP) for the purification of active enzymes (two different alcohol dehydrogenases); the IL is capable of stabilizing the enzymes and enhancing the solubility of hydrophobic substrates.…”

Extraction and stability of bovine serum albumin (BSA) using cholinium-based Good's buffers ionic liquids

“…IL-based ABS have been used for the extraction of proteins and enzymes, while demonstrating to provide higher extraction efficiencies than the traditional PEG-based ABS [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34]. Alkylimidazolium-based ILs combined with phosphate-based salts were the most widely investigated phase-forming components of ABS [15].…”

Extraction of vanillin using ionic-liquid-based aqueous two-phase systems

“…The initial interest on ILs as alternative extractive fluids results from their physical and chemical advantages, namely negligible flammability and vapour pressure, high solvation ability, high chemical stability, high selectivity, and easiness in recovering and recycling them [25][26][27][28][29]. Moreover, it was already shown that adequate ILs do not significantly inactivate enzymes ensuring thus their structural integrity and enzymatic activity [5,27].…”