Graphene Oxide Nanosheets Shielding of Lipase Immobilized on Magnetic Composites for the Improvement of Enzyme Stability

Abstract

In this study, a novel enzyme immobilization method was developed to enhance the catalytic stability of enzymes. In this strategy, ionic liquid (IL) modified magnetic chitosan (MCS) composites were used as supports for lipase adsorption and graphene oxide (GO) was employed as shell coating for the first time. The modifier used was imidazolium-based IL with a side alkyl chain which was composed of 8 −CH2 and a terminal hydroxyl group. The prepared supports IL-MCS, immobilized lipase PPL-IL-MCS, and GO/PPL-IL-MCS were well characterized. The GO shielding lipase GO/PPL-IL-MCS maintained high activity (2468 U/g), which was 6.72-fold of free lipase. In addition, the pH and temperature effect on lipase activity were investigated. The thermal stability, denaturants stability, storage stibility, and reusing stability were also studied. Compared to PPL-IL-MCS, the stabilities of GO/PPL-IL-MCS were all enhanced while keeping high activity. For example, after 10 cycles of reuse, the residual activity of GO/PPL-IL-MCS was 92.1%, which was higher than that of 88.4% for PPL-IL-MCS. Furthermore, the apparent K m of PPL-IL-MCS and GO/PPL-IL-MCS was 5.7 and 8.8 mg/mL, respectively, which were both lower than that of PPL-MCS (17.1 mg/mL). Circular dichroism (CD) was used to analyze the secondary structure of lipase to explain the mechanism of stable enhancement of immobilized enzyme. This work demonstrated that GO was used as a shell coating for the first time to improve the lipase stability. This immobilization method provides a reference for the immobilization of other kinds of enzymes.

Bio-Catalysis and Biomedical Perspectives of Magnetic Nanoparticles as Versatile Carriers

“…Ionic liquid-modified magnetic chitosan composites Lipase Adsorption Elevated catalytic activity (6.72-fold) as compared to the free enzyme Enhanced thermal stability and reusability retaining 92.1% of residual activity after 10 cycles of reuse. [24] Fe 3 O 4 magnetic nanoparticles functionalized with wheat gluten hydrolysates…”

“…Moreover, a significant increase in thermal stability profile indicates that zwitterionic polymer with shorter alkyl side chains is advantageous to develop thermostable enzymes [63]. Of most recent, Suo et al [24] developed a novel immobilization strategy to increase the catalytic stability of lipase enzyme. In this method, lipase was adsorbed on ionic liquid (IL) modified magnetic chitosan (MCS) composites and graphene oxide (GO) nanosheets served as shell coating for anchoring the lipase structure ( Figure 8) [24].…”

“…Of most recent, Suo et al [24] developed a novel immobilization strategy to increase the catalytic stability of lipase enzyme. In this method, lipase was adsorbed on ionic liquid (IL) modified magnetic chitosan (MCS) composites and graphene oxide (GO) nanosheets served as shell coating for anchoring the lipase structure ( Figure 8) [24]. The GO-shielded novel biocatalytic system sustained 6.72-fold high activity as compared to the free enzyme.…”

“…The GO-shielded novel biocatalytic system sustained 6.72-fold high activity as compared to the free enzyme. In addition, the thermal stability was also enhanced, and the immobilized enzyme retained 92.1% of residual activity after 10 cycles of reuse [24]. Wang et al [31] synthesized stable magnetic Fe 3 O 4 @chitosan nanoparticles by an efficient and simple in-situ co-precipitation technique and used to chemically conjugate lipase from Thermomyces lanuginosus by covalent immobilization.…”

Design of GO–Ag-functionalized Fe3O4@CS composite for magnetic adsorption of rhodamine B

“…applied a procedure as reported earlier to our previous work. [33][34][35] Briey, chitosan (0.3 g) was rstly dissolved in 50 mL acetic acid solution (1%, v/v) under mechanical stirring. Then Fe 3 O 4 NPs (2.0 g) was the added to chitosan solution.…”