The potential for performing cellulase-catalyzed reactions on cellulose dissolved in 1-butyl-3-methylimidazolium chloride ([bmim]Cl) has been investigated. We have carried out a systematic study on the irreversible solvent and ionic strength-induced inactivation and unfolding of cellulase from Trichoderma reesei (E.C. #3.2.1.4). Experiments, varying both cellulase and IL solvent concentrations, have indicated that [bmim]Cl, and several other ILs, as well as dimethylacetamide-LiCl (a well-known solvent system for cellulose), inactivate cellulase under these conditions. Despite cellulase inactivity, results obtained from this study led to valuable insights into the requirements necessary for enzyme activity in IL systems. Enzyme stability was determined during urea, NaCl, and [bmim]Cl-induced denaturation observed through fluorescence spectroscopy. Protein stability of a PEG-supported cellulase in [bmim]Cl solution was investigated and increased stability/activity of the PEG-supported cellulase in both the [bmim]Cl and citrate buffer solutions were detected.

A new method for introducing enzymes into cellulosic matrixes which can be formed into membranes, films, or beads has been developed using a cellulose-in-ionic-liquid dissolution and regeneration process. Initial results on the formation of thin cellulose films incorporating dispersed laccase indicate that active enzyme-encapsulated films can be prepared using this methodology and that precoating the enzyme with a second, hydrophobic ionic liquid prior to dispersion in the cellulose/ionic liquid solution can provide an increase in enzyme activity relative to that of untreated films, presumably by providing a stabilizing microenvironment for the enzyme.

Preparation of cellulose-polyamine composite films and beads, which provide high loading of primary amines on the surface allowing direct one-step bioconjugation of active species, is reported using an ionic liquid (IL) dissolution and regeneration process. Films and bead architectures were prepared and used as immobilization supports for laccase as a model system demonstrating the applicability of this approach. Performance of these materials, compared to commercially available products, has been assessed using millimeter-sized beads of the composites and the lipase-catalyzed transesterification of ethyl butyrate.

The ionic liquids (ILs) 1-butyl-3-methylimidizolium chloride ([C4mim]Cl), 1-butyl-3-methylimidizolium 2(2-methoxyethoxy)ethylsulfate ([C4mim][MDEGSO4]), and 1-butyl-1-methylpyrollidinium dihydrogenphosphate ([p1,4][DHP]) were tested for their effects on the crystallization of the proteins canavalin, β-lactoglobulin B, xylanase, and glucose isomerase, using a standard high throughput screen. The crystallization experiments were set up with the ILs added to the protein solutions at 0.2 and 0.4 M final concentrations. Crystallization droplets were set up at three protein/precipitant ratios (1:1, 2:1, and 4:1), which served to progressively dilute the effects of the screen components while increasing the equilibrium protein and IL concentrations. Crystals were obtained for all four proteins at a number of conditions where they were not obtained from IL-free control experiments. Over half of the protein−IL combinations tested had more successful outcomes than negative outcomes, where the IL-free crystallization was better than the corresponding IL-containing outcome, relative to the control. One of the most common causes of a negative outcome was solubilization of the protein by the IL, resulting in a clear drop. In one instance, we were able to use the IL-induced solubilizing to obtain β-lactoglobulin B crystals from conditions that gave precipitated protein in the absence of IL. The results suggest that it may be feasible to develop ILs specifically for the task of macromolecule crystallization.

New ionic liquids containing (2-hydroxypropyl)-functionalized imidazolium cations have been synthesized by the atom-efficient, room temperature reaction of 1-methylimidazole with acid and propylene oxide; the acid providing the anionic component of the resultant ionic liquids. The incorporation of the secondary hydroxyl-functionality in the cation causes some interesting modifications to the behavior of these ionic liquids, increasing hydrophilicity and resulting in the unprecedented formation of liquid-liquid biphases with acetone. The single crystal structure of 1-(2-hydroxypropyl)-3-methylimidazolium tetraphenylborate, prepared by metathesis of the corresponding chloride-containing ionic liquid, has also been determined.

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