(41g) Biocatalysis in Anhydrous Ionic Liquids

Enzymes can perform many industrially relevant reactions, such as esterification, hydrolysis, oxidation, reduction, and C-C bond formation, with high specificity and under significantly milder conditions than their chemical counterparts. They can perform these reactions on a wide range of substrates, making them highly attractive for many applications. As a result, research into the use of enzymes as industrial biocatalysts has been gaining ground, particularly in conjunction with emerging solvent systems such as ionic liquids. However, enzymes often have very low solubilities in nonaqueous environments and are frequently unstable, limiting the window of usability. Consequently, there is a need to develop new biotechnologies that improve solubility and stability of biocatalysts in nonaqueous media.

Surface modification of proteins, to yield protein-polymer surfactant nanoconjugates, has been demonstrated as a robust method for synthesizing protein-rich biofluids, devoid of any solvent. This new class of material has been shown to be a promising new technology where enzymes have been stabilized in non-aqueous environments. Using a variety of spectroscopic and scattering techniques, these novel biomaterials have been shown to allow for extreme enzyme thermal stability¹, stability against aggregation², and retained dynamics³ and function⁴. Importantly, biofluids of the industrially relevant enzyme lipase showed that enzyme activity was not only retained in the absence of water, but actually enhanced at temperatures up to and including 150 °C⁵.

Recently, we showed that protein-polymer surfactant nanoconjugates are soluble in both hydrophilic and hydrophobic ionic liquids, and we demonstrated that biomolecule architecture can be preserved in the non-aqueous environment. Furthermore, the solubilized protein displayed improved thermal stability as compared to aqueous solutions⁶. Here, we show recent results involving nanoconjugates of the enzyme β-glucosidase in anhydrous ionic liquids. Particularly, we demonstrate that the enzyme has significantly improved activity at 120 °C, and importantly, activity towards water insoluble cellulose. As a result, this nascent technology could provide a platform for biocatalysis in industrially relevant nonaqueous solvent systems.

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(2) Brogan, A. P. S. et al. J. Phys. Chem. B. 2013, 117, 8400–8407.

(3) Gallat, F.-X.; Brogan, A. P. S. et al. J. Am. Chem. Soc. 2012, 132, 13168–13171.

(4) Perriman, A. W.; Brogan, A. P. S. et al. Nat. Chem. 2010, 2, 622–626.

(5) Brogan, A. P. S. et al. Nat. Commun. 2014, 5, 5058.

(6) Brogan, A. P. S., and Hallett, J. P. J. Am. Chem. Soc. 2016. 138, 4494-4501.