Lipase enzymes on graphene oxide support for high-efficiency biocatalysis

Abstract

Enzymatic biocatalysis is of huge importance on an industrial scale. The main problem of enzymes is that they undergo denaturation. Here, we demonstrate that stability and activity of the enzymes can be enhanced by their immobilization on graphene oxide. We show this by an example of biosynthesis of industrially highly important acylglycerols using lipase enzymes. The synthesis of mono-, di- and triacylglycerols is of huge technological importance in pharmaceutical as well as food and chemical industries. Since the mono- and diacylglycerols can be synthesized by chemical reactions only with several difficulties, the enzyme-catalyzed reactions are used. We demonstrate successful immobilization of lipases from Rhizopus oryzae, Candida rugosa and Penicillium camemberti on the surface of graphene oxide. The immobilized enzymes exhibit high stability as well as retain high activity in protic and aprotic polar solvents reaching up to 146% of immobilized lipase from P. camemberti activity in iso-propanol compared to non-incubated immobilized enzyme. The activity retention after the incubation in non-polar solvents like toluene and hexane was comparable to that of those not exposed to the organic solvent (100% relative activity). The immobilized lipases were shown to exhibit catalytic performance for esterification of glycerol and a series of fatty acids in hexane. Our results support suitability of immobilized lipases on graphene oxide as catalyst for monoacylglycerols and diacylglycerol syntheses. These products represent high value-added materials with application as biologically active pharmaceutical substances, synthetic building blocks, in the lipid modification of drugs and proteins, or in the effective synthesis of surfactants. The enhanced stability and activity of the enzymes may result in major application of graphene oxide on an industrial scale.