Glucose oxidase catalyses the reduction of O2 to H2O2 in the presence of irradiated TiO2 and isopropyl alcohol

Abstract

Catalytic amounts of glucose oxidase from Aspergillus niger (GO) are active in the reduction of O2 to H2O2 in the presence of irradiated suspensions of TiO2 and isopropyl alcohol as electron donor. An explanation of this behaviour is given on the basis of the ability of the enzyme to capture electrons from the photoexcited TiO2 instead of its natural substrate, glucose. This process has a marked positive effect on both the oxidation of isopropyl alcohol to acetone and the formation of radical intermediates, which have been detected, for the first time, by EPR-spin trapping investigation.

Photo-electro-chemical properties of TiO2 mediated by the enzyme glucose oxidase

“…5C the results obtained with 2-propanol already published in Ref. [22]. We observe that in all cases the formation rate of the adducts between pbn and the alkoxy radicals increases significantly in the presence of GO, thus indicating that in any case the enzyme has a positive effect on the oxidation rate of the alcoholic substrate to the corresponding radical species.…”

“…Therefore, we expected that the presence of the enzyme may also affect the photocatalytic properties of this semiconductor towards organic substrates that can be oxidized by these reactive intermediates. We have previously found that GO has a marked positive effect on the oxidation of 2-propanol [22]. Herein, this study is extended to other alcoholic substrates.…”

“…Its reduction products ( also take part effectively in the overall oxidation process [18][19][20]. Prior work by our group has been devoted to preparing and characterising composite systems in which natural enzymes [21,22] or their synthetic models [1,9,13], adsorbed or chemically linked to the semiconductor surface, enhance the efficiency of the electron transfer from photoexcited TiO 2 to O 2 . In particular, we have recently shown that this process can be positively affected by the presence of catalytic amounts of glucose oxidase (GO), EC 1.1.3.4, from Aspergillus niger (GO) [22].…”

“…In our previous investigations about the effect of GO on the photocatalytic properties of TiO 2 , we proposed that this enzyme is able to mediate the electron transfer process from irradiated TiO 2 to O 2 according to Equation (2) [22]. These experiments were carried out in the presence of isopropyl alcohol as h vb + scavenger:…”

“…Prior work by our group has been devoted to preparing and characterising composite systems in which natural enzymes [21,22] or their synthetic models [1,9,13], adsorbed or chemically linked to the semiconductor surface, enhance the efficiency of the electron transfer from photoexcited TiO 2 to O 2 . In particular, we have recently shown that this process can be positively affected by the presence of catalytic amounts of glucose oxidase (GO), EC 1.1.3.4, from Aspergillus niger (GO) [22]. This is a flavoprotein (MW = 150 kDa) that catalyses the reduction of O 2 to H 2 O 2 with the simultaneous oxidation of b-D-glucose to Dglucono-1,5-lactone [23].…”