Artificial photosynthesis by microbe-semiconductor biohybrid systems has been demonstrated as a valuable strategy in providing sustainable energy and in carbon fixation . However, most of the developed biohybrid systems for light harvesting employ heavy metal materials, especially cadmium sulfide (CdS), which normally cause environmental pollution and restrict the widespread of the systems. Herein, we constructed an environmentally friendly biohybirid system based on a typical acetogenic bacteria, Moorella thermoacetica , coupling with a carbon-based semiconductor, graphitic carbon nitride (g-C 3 N 4 ), to realize light-driven carbon fixation . The proposed biohybrid system displayed outstanding acetate productivity with a quantum yield of 2.66 ± 0.43 %. Non-targeted proteomic analysis indicated that the physiological activity of the bacteria was improved, coupling with the non-toxic material. We further proposed the mechanisms of energy generation, electron transfer and CO 2 fixation of the irradiated biohybrid system by proteomic and metabolomic characterization. With the photoelectron generated in g-C 3 N 4 under illumination, CO 2 is finally converted to acetate via the Wood-Ljungdahl pathway (WLP). Other associated pathways were also proved to be activated, providing extra energy or substrates for acetate production. The study reveals that the future focus of the development of biohybrid systems for light harvesting can be on the metal-free biocompatible material, which can activate the expression of the key enzymes involved in the electron transfer and carbon metabolism under light irradiation .
The integration of microorganisms and photosensitizers presents a promising approach to chemical production utilizing solar energy. However, the current system construction process remains complex. Herein, we introduce a straightforward and efficient solar-to-chemical conversion system that combines the dissolved photosensitizer Eosin Y with the non-photosynthetic bacterium Moorella thermoacetica . Under light radiation, acetate production increased to 5.1 µM h −1 µM −1 catalyst, exceeding the previously reported maximum by 5.9-fold, with a quantum efficiency of 17.6%. The soluble photosensitizer EY can penetrate the cell and directly engage in intracellular energy metabolism, significantly enhancing intracellular ATP and NADPH/NADP + levels. Within this biohybrid system, sacrificial agent triethanolamine played a dual role: (1) providing continuous photoelectron generation by Eosin Y, enhancing intracellular reducing power, and facilitating carbon fixation via the Wood-Ljungdahl pathway; and (2) its oxidation product, formaldehyde, served as a critical intermediate and a direct precursor for methylenete-trahydrofolate in the Wood-Ljungdahl pathway, consequently simplifying reaction steps and markedly boosting acetate yield. This study provides a simple microorganism-photosensitizer biohybrid system to produce acetate and light on the multifaceted roles of sacrificial agents, paving the development of efficient solar energy conversion with nonphotosynthetic bacteria.
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