A comprehensive study on rational biocatalysts and individual components of photobiocatalytic H₂ production systems

Photobiocatalytic system has been developing as a promising approach for H₂ production. Herein, the rational characteristics of biocatalysts and the role of individual components affecting the efficiency of the system were investigated. Photocatalytic studies showed that tris (2-amino-2-hydroxymethyl-1,3-propanediol) was an ideal electron donor for viologen reduction by TiO₂. Biocatalytic reaction revealed that cell permeability, the redox potential of electron mediators and the cell envelope were crucial to the activity of whole-cell biocatalysts. In photobiocatalytic system, recombinant Escherichia coli with a turnover frequency of 39.43 ± 3.77 s⁻¹ based on [FeFe]-hydrogenase activity was a more rational biocatalyst than Anabaena variabilis. A comprehensive study found that the presence of TiO₂, light and biocatalysts strongly enhanced H₂ production, whereas Tris and MV²⁺ had less influence. A maximum rate was found at 16.73 ± 1.03 μmol/min with a solar-to-H₂ conversion of 1.58 ± 0.10 %. Understanding the role of each component will guide the development of high-efficient photobiocatalysis.