Redox-Polymer-Wired [NiFeSe] Hydrogenase Variants with Enhanced O2 Stability for Triple-Protected High-Current-Density H2 -Oxidation Bioanodes.

ABSTRACT: Variants of the highly active [NiFeSe] hydrogenase from D.?vulgaris Hildenborough that exhibit enhanced O2 tolerance were used as H2 -oxidation catalysts in H2 /O2 biofuel cells. Two [NiFeSe] variants were electrically wired by means of low-potential viologen-modified redox polymers and evaluated with respect to H2 -oxidation and stability against O2 in the immobilized state. The two variants showed maximum current densities of (450±84)??A?cm-2 for G491A and (476±172)??A?cm-2 for variant G941S on glassy carbon electrodes and a higher O2 tolerance than the wild type. In addition, the polymer protected the enzyme from O2 damage and high-potential inactivation, establishing a triple protection for the bioanode. The use of gas-diffusion bioanodes provided current densities for H2 -oxidation of up to 6.3?mA?cm-2 . Combination of the gas-diffusion bioanode with a bilirubin oxidase-based gas-diffusion O2 -reducing biocathode in a membrane-free biofuel cell under anode-limiting conditions showed unprecedented benchmark power densities of 4.4?mW?cm-2 at 0.7?V and an open-circuit voltage of 1.14?V even at moderate catalyst loadings, outperforming the previously reported system obtained with the [NiFeSe] wild type and the [NiFe] hydrogenase from D.?vulgaris Miyazaki?F.

SUBMITTER: Ruff A 

PROVIDER: S-EPMC7497094 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature