Characteristics and applications of extracellular polymeric substances of electroactive microorganisms

Abstract:

Electroactive microorganisms can exchange electrons in their extracellular environment with electrodes or other cells through direct contact, conductive pilli, or redox mediators, in which extracellular polymeric substances (EPS) play a crucial part. EPS are a mixture of cell secretions, cell lysates, and other substances attached on the surface of microbial cells to protect them from external environment, comprising proteins, polysaccharides, humics, among others. Thus, the composition and characteristics of EPS from electroactive microorganisms influence the electroactive properties of the EPS and the extracellular electron transfer of the microorganisms, allowing them to be applied in the environmental bioremediations. For a clear understanding of the electroactive properties of EPS from electroactive microorganisms and the influence on extracellular electron transfer of the microorganisms, we introduced the methods for characterizing the electroactive properties of the EPS and summarized the influence of the composition, chemical properties, physical properties, and spatial distribution of the substances on their electroactive properties. In addition, we descried the applications of the EPS in decolorization of dye wastewater, adsorption of heavy metals, biotransformation of organic pollutants, leachate management, etc. Finally, the future research directions in the characterization method, the scale of experiments, and the interaction mechanisms were summed up.