Modular engineering a Shewanella oneidensis–CdS@rGO artificial photosynthetic biohybrid to accelerate photoelectron transfer and conversion for enhanced hydrogen production

Abstract

Photocatalytic inorganic–biological hybrid systems have emerged as a promising approach to improve hydrogen production efficiency. However, the slow rate of interfacial photoelectron transfer, the inefficient transmembrane photoelectron uptake, and the poor intracellular photoelectron conversion still limit the efficiency of hydrogen production. Herein, we adopted a modular engineering strategy to construct a Shewanella oneidensis–CdS@rGO artificial biohybrid photosynthetic system to enhance hydrogen production. First, to increase the rate of transmembrane photoelectron uptake, we constructed a highly conductive transmembrane channel to take up photoelectrons by screening and optimizing the outer membrane c-cytochrome OmcF from Geobacter sulfurreducens, thereby enhancing the photoelectron flux. Second, to improve the efficiency of intracellular photoelectron conversion, the hydrogenase HydA_dds from Desulfovibrio desulfuricans was screened and optimized to enhance the expression of periplasmic hydrogenase. Upon assemblage of the above two modules, both photoelectron flux and hydrogenase activity were significantly enhanced, leading to a hydrogen yield of 493.7 ± 26.5 μmol mg⁻¹. Finally, to accelerate the rate of interfacial photoelectron transfer between CdS nanoparticles and cells, a high-speed conductive network was constructed with rGO on the cell surface in the artificial photosynthetic biohybrid system, which led to a final hydrogen yield of 643.1 ± 40.3 μmol mg⁻¹. To the best of our knowledge, this is the highest hydrogen yield among reported biohybrid systems constructed from Shewanella. This study significantly enhanced the hydrogen production of biohybrid systems by increasing transmembrane photoelectron uptake, improving intracellular photoelectron conversion, and accelerating interfacial photoelectron transfer, which provided a potential avenue for further optimization of artificial photosynthetic biohybrids.