Internalized nanoparticles trigger metabolic reconfiguration to enhance extracellular electron transfer in microalgal biophotoelectrochemical cells

초록

Microalgal biophotoelectrochemical cells (BPEC) offer a sustainable route for simultaneous wastewater treatment and bioenergy production. However, their efficiency is currently constrained by inefficient extracellular electron transfer (EET). This study demonstrated that the co-internalization of light-harvesting nanoparticles (LHN) and conductive nanoparticles (CN) into Scenedesmus quadricauda significantly amplified bioelectrochemical performance, a phenomenon supported by correlative transcriptomic analysis. The maximum current density produced by microalgae with co-internalized carbon dots (CD) as LHN and titanium dioxide (TiO2) as CNs increased to 79.0 μA/cm2 compared to the control (34.3 μA/cm2), while chemical oxygen demand (COD) removal efficiency and biodiesel yield improved 1.8-fold and 1.5-fold, respectively. Ultrastructural and elemental mapping analysis confirmed a specific spatial arrangement in which CDs were in the cytoplasm in close proximity to photosynthetic thylakoids and TiO2 nanoparticles were positioned within the cell envelope, including the cell membrane and cell wall. Transcriptomic profiling suggested that the nanoparticles provided a correlational molecular framework that supported enhanced EET. While genes encoding light-harvesting complexes, electron transport carriers, and ribosomal machinery were significantly up-regulated to boost EET, energy-intensive peripheral pathways were down-regulated. Overall, this study provided correlative molecular evidence suggesting that nanoparticles reconfigured algal metabolism to improve cellular hardware for high-efficiency bioenergy production, offering a foundational strategy for advanced BPEC.

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