Abstract
New Candida antarctica lipase B derivatives with higher activity than the free enzyme were obtained by occlusion in an organogel of an ionic liquid (ionogel) based on the ionic liquid [Omim][PF6] and polyvinyl chloride. The inclusion of glutaraldehyde as a crosslinker improved the properties of the ionogel, allowing the enzymatic derivative to reach 5-fold higher activity than the free enzyme and also allowing it to be reused at 70 °C. The new methodology allows enzymatic derivatives to be designed by changing the ionic liquid, thus providing a suitable microenvironment for the enzyme. The ionic liquid may act on substrates to increase their local concentration, while reducing water activity in the enzyme’s microenvironment. All this allows the activity and selectivity of the enzyme to be improved and greener processes to be developed. The chemical composition and morphology of the ionogel were also studied by scanning electron microscopy–energy dispersive X-ray spectroscopy, finding that porosity, which was related with the chemical composition, was a key factor for the enzyme activity.
Highlights
In recent decades, ionic liquids have demonstrated their potential for use as reaction and separation media
Activity of Ionogel-Derivatives were generally found to be suitable for biocatalytic reactions, while the water-miscible ionic liquids
ILs [20], with thewere enzyme molecules, which lead to protein denaturation or stripping off the essential the negative effect observed on the lipase activity can be attributed to the direct interaction of the water associated with the enzyme [21,22,23]
Summary
Ionic liquids have demonstrated their potential for use as reaction and separation media. In separation applications, they have been used as liquid–liquid biphasic systems [1,2] and as liquid phase in supported liquid membranes and polymer inclusion membranes [3,4,5]. The advantages of using ionic liquids instead of organic solvents as reaction media for biocatalysis include their ability to enhance enzyme activity as well as their selectivity and stability [6,7,8,9,13]. Enzymes must be immobilized in order to increase their stability in operational conditions and allow their reuse. Among the different methods that can be used to immobilize enzymes, encapsulation is of particular interest because of Molecules 2020, 25, 3233; doi:10.3390/molecules25143233 www.mdpi.com/journal/molecules
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