Abstract
Bioelectrochemical systems (BESs) are emerging as attractive routes for sustainable energy generation, environmental remediation, bio-based chemical production and beyond. Electron shuttles (ESs) can be reversibly oxidized and reduced among multiple redox reactions, thereby assisting extracellular electron transfer (EET) process in BESs. Here, we explored the effects of 14 ESs on EET in Shewanella oneidensis MR-1, and found that anthraquinone-2-sulfonate (AQS) led to the highest cathodic current density, total charge production and reduction product formation. Subsequently, we showed that the introduction of -OH or -NH2 group into AQS at position one obviously affected redox potentials. The AQS-1-NH2 exhibited a lower redox potential and a higher Coulombic efficiency compared to AQS, revealing that the ESs with a more negative potential are conducive to minimize energy losses and improve the reduction of electron acceptor. Additionally, the cytochromes MtrA and MtrB were required for optimal AQS-mediated EET of S. oneidensis MR-1. This study will provide new clues for rational design of efficient ESs in microbial electrosynthesis.
Highlights
Energy crisis and environmental pollution are one of the major global issues that the world is facing today
We found that the MtrA and MtrB components were essential for the AQS-mediated electron transfer (EET) of S. oneidensis MR-1, and the c-type cytochromes OmcA and MtrC accounted for partially 82% of cathodic electron flows
Given that the electrochemical properties of various Electron shuttles (ESs) might be distinct in microbial electrosynthesis (MES), the screen of optimal ESs for specific electro-active bacteria will contribute to the highly efficient electron transfer to endproduct production
Summary
Energy crisis and environmental pollution are one of the major global issues that the world is facing today. The bioelectrochemical system (BES), including microbial fuel cell (MFC) and microbial electrosynthesis (MES), has been regarded as a promising technology for energy generation, resource recovery, environmental remediation, and chemical production (Bajracharya et al, 2016; Chen et al, 2020a; Naha et al, 2020; Rout et al, 2020). In a MFC system, the microorganisms transfer electrons to a solid-substrate for the generation of electrical power coupled to the oxidation of organic or inorganic matters in the wastewater (Santoro et al, 2017). MES reverses the direction of electron transfer from a cathode to microbes for the microbial production of value-added fuels or chemicals (Rabaey and Rozendal, 2010; Das et al, 2020). MES enables the biocatalysts to use a variety of clean and renewable electricity-sources, including solar, wind, geothermal, biomass, hydropower and surpluses electricity from the power grid (Zhang, 2015).
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