Under visible light, non-photosynthetic microorganism/semiconductor has recently shown promising applications in biofuel production, bioenergy generation and pollutant removal. However, the understanding of electron transfer mechanism at the biotic-abiotic interface is limited. Herein, mixed culture/carbon nitride and pure culture (Stenotrophomonas maltophilia HP14)/carbon nitride were constructed to reveal the energy conversion pathway under visible light. Enhanced electron transfer was observed on the biotic-abiotic interface. The photocurrent of non-photosynthetic S. maltophilia HP14/g-C3N4/ITO with riboflavin addition was 10.2-fold higher than that of g-C3N4/ITO control. As the electron donor, S. maltophilia HP14 transfer bio-electrons to self-secreted riboflavin and valence band of semiconductor. Riboflavin (RF) accept bio-electrons and photogenerated electrons to form 1,5-dihydroflavin (RFH2). While RFH2 is able to transfer electrons to the valence band of carbon nitride and transform into RF again. However, riboflavin is not stable under visible light irradiation, which may lead to a decreased photocurrent. This study demonstrated the role of redox active compounds at the microorganism/semiconductor interface and described a possibility for non-photosynthetic microorganisms to capture and utilize visible light.
Keywords: Carbon nitride; Extracellular electron transfer; Non-photosynthetic microorganism; Riboflavin.
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