Enhanced photo-fermentative hydrogen production in photosynthetic bacteria via nano-Fe3O4-improved photosynthetic electron transfer efficiency.

Photo-fermentative hydrogen production is a green and sustainable technology for recovering resources from pollutants. In the context of photo-fermentative hydrogen production in photosynthetic bacteria, the efficiency of the photosynthetic chain is a decisive factor for the supply of electrons and energy. In this study, the biocompatible conductor nano-Fe₃O₄ was fed to Rhodopseudomonas palustris and embedded within the cell membrane, with the objective of enhancing the photosynthetic chain efficiency for hydrogen production. The maximum hydrogen production increased by 36 %, and the hydrogen yield reached 3.46 mol H₂/mol glucose. The activity of both the nitrogenase and the ATP synthase, which are involved in the hydrogen-producing metabolism, was observed to be more vigorous with the addition of nano-Fe₃O₄. The photocurrents of R. palustris increased from 17.5 nA to 19 nA after feeding nano-Fe₃O₄, indicating that nano-Fe₃O₄ enhanced the efficiency of the photosynthetic chain. Transcriptomics, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy revealed that nano-Fe₃O₄ partially substitute for cytochrome C, which could facilitate electron transfer in the photosynthetic chain and enhance hydrogen production.