Pore size effect of MgO-templated carbon on enzymatic H2 oxidation by the hyperthermophilic hydrogenase from Aquifex aeolicus

Hydrogenase from the hyperthermophilic bacterium Aquifex aeolicus was immobilized in MgO-templated carbon (MgOC). Two different pore sizes were investigated, large pore size of 150 nm (MgOC150) and smaller pore size of 35 nm (MgOC35). Direct H-2 oxidation proceeded in both MgOC150 and MgOC35. Hydrogenase embedded in the carbon material exhibited the expected properties in terms of onset for H-2 oxidation and kinetics of formation of the inactive state at high potentials, whatever the size of the pores. Pore size much larger than the size of the enzyme favored the loading of the enzyme, yielding to high catalytic current reported to the capacitance. Pore size closer to the enzyme diameter, as determined by DLS, enhanced the stability of the enzyme at high temperature.