Glucose Oxidase Immobilized on Magnetic Zirconia: Controlling Catalytic Performance and Stability

Abstract

Here, we report the structures and properties of biocatalysts based on glucose oxidase (GOx) macromolecules immobilized on the mesoporous zirconia surface with or without magnetic iron oxide nanoparticles (IONPs) in zirconia pores. Properties of these biocatalysts were studied in oxidation of Dglucose to D-gluconic acid at a wide range of pH and temperatures. We demonstrate that the calcination temperature (300, 400, or 600 °C) of zirconia determines its structure, with crystalline materials obtained at 400 and 600 °C. This, in turn, influences the catalytic behavior of immobilized GOx, which was tentatively assigned to the preservation of GOx conformation on the crystalline support surface. IONPs significantly enhance the biocatalyst activity due to synergy with the enzyme. At the same time, neither support porosity nor acidity/basicity shows correlations with the properties of this biocatalyst. The highest relative activity of 98% (of native GOx) at a pH 6−7 and temperature of 40−45 °C was achieved for the biocatalyst based on ZrO 2 calcined at 600 °C and containing IONPs. This process is green as it is characterized by a high atom economy due to the formation of a single product with high selectivity and conversion and minimization of waste due to magnetic separation of the catalyst from an aqueous solution. These and an exceptional stability of this catalyst in 10 consecutive reactions (7% relative activity loss) make it favorable for practical applications.

Magnetic Nanoparticle-Containing Supports as Carriers of Immobilized Enzymes: Key Factors Influencing the Biocatalyst Performance

“…[ 31 , 32 , 33 , 34 , 35 , 36 , 37 ]. To create an appreciable magnetic moment for a successful separation, magnetic NPs are often organized into clusters [ 34 , 38 ], imbedded in gels [ 36 ], other polymer or inorganic matrices [ 13 , 39 , 40 , 41 ], or self-assembled into larger structures [ 42 , 43 ]. This creates interparticle interactions and increases magnetic attraction between magnetic NPs and an external magnetic field.…”

“…An especially fascinating enhancement of the enzyme activity was observed when both enzyme and iron oxide NPs were located in the vicinity of each other. The comparison of the activities of glucose oxidase (GOx) immobilized in porous silica (SiO 2 ), alumina (Al 2 O 3 ), and zirconia (ZrO 2 ), or in the same supports but containing magnetite NPs in the support pores (Fe 3 O 4 -SiO 2 , Fe 3 O 4 -Al 2 O 3 , Fe 3 O 4 -ZrO 2 ), revealed that biocatalysts based on magnetic supports are noticeably more active than those based on non-magnetic supports [ 13 , 41 ]. Figure 3 shows a trend for ZrO 2 and Fe 3 O 4 -ZrO 2 supports [ 41 ].…”

“…The comparison of the activities of glucose oxidase (GOx) immobilized in porous silica (SiO 2 ), alumina (Al 2 O 3 ), and zirconia (ZrO 2 ), or in the same supports but containing magnetite NPs in the support pores (Fe 3 O 4 -SiO 2 , Fe 3 O 4 -Al 2 O 3 , Fe 3 O 4 -ZrO 2 ), revealed that biocatalysts based on magnetic supports are noticeably more active than those based on non-magnetic supports [ 13 , 41 ]. Figure 3 shows a trend for ZrO 2 and Fe 3 O 4 -ZrO 2 supports [ 41 ]. This effect was assigned to the inherent enzyme-like activity of iron oxide NPs [ 47 , 48 , 49 ], which leads to an enhancement of the activity of immobilized GOx due to a synergetic effect.…”

“…IO stands for Fe 3 O 4 NPs, while 600 indicates the temperature at which ZrO 2 was treated. Reproduced with permission from [ 41 ], the American Chemical Society, 2020.…”

“…[31][32][33][34][35][36][37]. To create an appreciable magnetic moment for a successful s NPs are often organized into clusters [34,38], imbedded in gels [36], o organic matrices [13,[39][40][41], or self-assembled into larger structures interparticle interactions and increases magnetic attraction between m external magnetic field. In the case of polymers utilized in the bioca NPs can be formed separately and then mixed with the polymers, a done for cellulose, because of its limited solubility [33].…”