Redox properties of extracellular polymeric substances (EPS) from electroactive bacteria

Abstract

Although the capacity for electroactive bacteria to convert environmental metallic minerals and organic pollutants is well known, the role of the redox properties of microbial extracellular polymeric substances (EPS) in this process is poorly understood. In this work, the redox properties of EPS from two widely present electroactive bacterial strains (Shewanella oneidensis and Pseudomonas putida) were explored. Electrochemical analysis demonstrates that the EPS extracted from the two strains exhibited redox properties. Spectroelectrochemical and protein electrophoresis analyses indicate that the extracted EPS from S. oneidensis and P. putida contained heme-binding proteins, which were identified as the possible redox components in the EPS. The results of heme-mediated behavior of EPS may provide an insight into the important roles of EPS in electroactive bacteria to maximize their redox capability for biogeochemical cycling, environmental bioremediation and wastewater treatment.

Microbial fuel cell‐mediated lignin depolymerization: a sustainable approach

“…This EPS seems to be quite helpful for cell‐to‐cell and cell‐to‐anode surface adherence. Redox properties of EPS produced by electroactive Shewanella oneidensis and Pseudomonas putida were explored previously . EPS helps in biofilm formation and increasing the surface area for the electron transfer from bacterial cell to anode.…”

Novel application of magnetic nano-carbon composite as redox mediator in the reductive biodegradation of iopromide in anaerobic continuous systems

“…EET process mediated by redox shuttles is an important microbial electron transfer pathway due to the presence of extracellular polymeric substances (EPS), which contain electron transport species in the gap between cells and electron acceptor/donor substances (Marsili et al 2008; Xiao et al 2017). In this sense, it has been reported that EPS from electroactive microorganisms exhibit redox activity due to the presence of proteins, humic substances, flavins and c-type cytochrome enzymes, serving as electron transfer mediators in EPS (Cervantes et al 2007; Flemming et al 2007; Marsili et al 2008; Li et al 2016b; Xiao et al 2017). The redox properties of EPS play an important role in the redox conversion of pollutants, such as U(VI) (Canstein et al 2008; Cao et al 2011), nitrobenzene (Wang et al 2013) and azo dyes (Kudlich et al 1997).…”

Extracellular polymeric substances are transient media for microbial extracellular electron transfer

“…Many components of EPS, such as DNA, humic acids, and some proteins, are redox-active or conductive/semiconductive ( 16 ). Some studies have shown that EPS are able to synthesize metal nanoparticles in the presence of c-type cytochromes ( 17 ) and have redox properties similar to MR-1 ( 18 ). However, it is poorly understood whether EPS are directly involved in EET processes, because previous microbial EET studies were only conducted on biofilms with EPS retained or on cells from the log stage or early steady stage cultures with little EPS.…”