Visible light-driven <italic>Methanosarcina barkeri-</italic>natural carbon-based semiconductor for methane production

The reduction of carbon dioxide to methane with high calorific values by a semi-artificial photosynthetic system (nonphotosynthetic microorganism-semiconductor biohybrids) contributes to the alleviation of the global greenhouse effect and energy crisis. As a key component, the structure and properties of semiconductor nanoparticles significantly affect the biohybrid performance. In this study, rape pollen is used as the raw material to successfully construct Methanosarcina barkeri-natural carbon-based semiconductor biohybrids (M. barkeri-NCS) for carbon dioxide reduction to methane. The results indicate that the prepared natural carbon-based semiconductors have distinct advantages, such as a good visible light response and a large pore volume. Meanwhile, the M. barkeri-NCS biohybrids have excellent photoelectrical properties, and the methane yield of which reaches up to 51±4.5 μmol/g under visible light irradiation (1.0±0.2 mW/cm²). The performed real-time quantitative polymerase chain reaction (qPCR) analysis further reveals that the genes related to the membrane-bond hydrogenase and cytochrome of M. barkeri, especially EchB (2.47±0.25 times) and VhtC (2.83±0.15 times), are significantly up-regulated, indicating their key roles in photoelectron transfer, trap, and utilization. The results are expected to provide theoretical support for constructing an efficient semi-artificial photosynthetic system.