Light-driven biological hydrogen production by Escherichia coli mediated by TiO2 nanoparticles

Photocatalytic hydrogen production using an inorganic bio-hybrid system can contribute to the proficient utilization of light energy, but it would necessitate the development of novel approaches for preparing a new hydrogen-producing biocatalyst. In this study, we developed a hybrid system to produce hydrogen, whereby the highly efficient light-harvesting inorganic semiconductor (TiO2) was mixed with Escherichia coli to form a biocatalyst with the addition of an electron mediator (MV2+) under different visible light irradiation. Under this hybrid system, the hydrogen production by E. coli was light intensity-dependent showing maximum production at 2000 W m−2, with a 2-fold increase in the hydrogen production compared to that without TiO2. The experiments on the continued cycle of hydrogen production revealed that the production could be continued for at least 3 cycles of 5 h incubation for each. A possible pathway utilizing glucose for hydrogen production by the hybrid system was proposed based on the analysis of the levels of metabolites. A feasibility study was also conducted using natural sunlight for hydrogen production by the hybrid system. Overall results demonstrated that whole cells of E. coli could be employed for photocatalytic hydrogen production where the intactness of the E. coli was retained under experimental conditions.