The Role of Hydrogenases and F0F1-ATPase in Electricity Generation in an H2-Based Bioelectrochemical System

Abstract

Hydrogenases (Hyds) are microbial enzymes that reversibly catalyze the oxidation of molecular hydrogen (H₂), playing a critical role in biohydrogen metabolism [1-3]. These include oxygen-resistant biological [NiFe]-hydrogenases, which have attracted great interest for their application in hydrogen fuel cell (H₂-FC) technologies. The results provide insight into the potential of bioelectrochemical-based systems for sustainable energy production. The bioelectrocatalytic efficiency of E. coli bacteria immobilized on the electrode surface in a volume of 3 μl (1.5 mg cell dry weight) was studied under the conditions of 0.2% glucose fermentation in peptone medium at pH-7.5 [4]. In this study, the electrochemical measurements were performed using a two-electrode system equipped with a computer potentiostat, specifically a hydrogen fuel cell voltammetry (HFCV). The wild-type E. coli BW25113, the septuple (BW25113hyaB hybC hycA fdoG ldhA frdC aceE) the F₀F₁-ATPase-defective, and the Hyd defective hyaB, hybC, hycE, hyfG mutant strains were used in the experiments. Maximal catalytic activity was observed in the hyaB and hyfG mutants, being stimulated ∼2-fold and ∼1.6-fold compared to the wild type, reaching values of ∼1.26 ± 0.02 V and ∼0.98 ± 0.02 V, respectively. The effect of the 10 mM N,N′-dicyclohexylcarbodiimide (DCCD), the F₀F₁-ATPase inhibitor, on the catalytic activity of Hyd enzymes was observed. It was shown that for all strains, the reading of the voltammeter decreased ~1.5 times, reaching the readings recorded by the F₀F₁-ATPase-defective strain. Interestingly, in the case of the the septuple mutant strain, DCCD recorded a stimulating rather than a suppressive effect. The results obtained indicate the great potential of bacteria as anodic biocatalysts and demonstrate the need for further studies.