Chapter 3.6 - Diversity of Extreme Electroactive Microorganisms and Their Bioelectrochemical Applications

Abstract

Electroactive microorganisms (EAMs) are used as biocatalysts in bioelectrochemical systems for various applications ranging from wastewater treatment and biosensing to the production of bioenergy and biochemicals. Transfer or uptake of electrons extracellularly to or from solid-state electron acceptors or donors is a unique metabolic feature of EAMs. Several pure and enriched mixed microbial cultures have been used in different microbial electrochemical technologies Though the research on METs is growing rapidly, some limiting factors, such as low electrolyte conductivity, high system internal resistance, and sluggish microbial electron transfer rate, affect their overall performance or targeted applications. The microorganisms from extreme habitats, such as high salinity, alkalinity, and elevated temperature, can overcome the limitations associated with electrolyte conductivity and electron transfer. Thus, using extremophiles is considered a feasible means to improve the efficiency of various METs and develop niche-specific applications under extreme conditions. In this chapter, we first briefly introduce bioelectrochemical systems (BESs), extremophilic EAMs, extracellular electron transfer processes, and the benefits of using extremophilic microbes in BESs. It is followed by comprehensive information on the diversity of extremophilic EAMs and their use in microbial electrochemistry-based applications, such as energy production, wastewater treatment, and the production of value-added chemicals. Lastly, a well-studied thermophilic EAM Thermincola ferriacetica is discussed regarding its electroactivity and the extracellular electron transfer mechanism.