Journal
ENVIRONMENTAL SCIENCE & TECHNOLOGY
Volume 54, Issue 12, Pages 7217-7225Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.est.0c00141
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Funding
- National Natural Science Foundations of China [41701305, 41977028]
- Pearl River S&T Nova Program of Guangzhou [201906010060]
- Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education [201705]
- Guangdong Special Support Plan for High-Level Talents [2017TX04Z175]
- Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program [2017BT01Z176]
- Guangdong Academy of Science Project of Science and Technology Development [2018GDASCX-0930, 2018GDASCX-0106, 2018GDASCX-0501]
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Exogenous electron mediators (EMs) can facilitate extracellular electron transfer (EET) via electron shuttling processes, but it is still unclear whether and how biofllm formation is affected by the presence of EMs. Here, the impacts of EMs on EET and biofilm formation were investigated in bioelectrochemical systems (BESs) with Shewanella oneidensis MR-1, and the results showed that the presence of five different EMs led to high density current production. All the EMs substantially promoted biofilm formation with 15-36 times higher total biofilm DNA with EMs than without EMs, and they also increased the production of extracellular polymeric substances, which was favorable for biofilm formation. The current decreased substantially after removing EMs from the medium or by replacing electrodes without biofllm, suggesting that both biofilm and EMs are required for high density current production. EET-related gene expression was upregulated with EMs, resulting in the high flux of cell electron output. A synergistic mechanism was proposed: EMs in suspension were quickly reduced by the cells and reoxidized rapidly by the electrode, resulting in a microenvironment with sufficient oxidized EMs for biofilm formation, and thus, besides the well-known electron shuttling process, the EM-induced high biofilm formation and high Mtr gene expression could jointly contribute to the EET and subsequently produce a high density current. This study provides a new insight into EM-enhanced current production via regulating the biofllm formation and EET-related gene expression.
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