Bioenergy Derived from Electrochemically Active Biofilms

Abstract

Microorganisms (bacteria) naturally form biofilms on solid surfaces. Biofilms can be found in a variety of natural sites, such as sea water sediments, soils, and a range of wastewaters, such as municipal, dye, agricultural, and industrial wastewaters. The biofilms are normally dangerous to human health due to their inherited robustness. Electrochemically active biofilms (EABs) generated by electrochemically active microorganisms (EAMs) have potential applications in bioenergy production, green chemical synthesis, bioremediation, bio-corrosion mitigation, and biosensor development. EABs have attracted considerable attention in bioelectrochemical systems, such as microbial fuel cells (MFCs) and microbial electrolysis cells, where they act as living bio-anode or bio-cathode catalysts. EABs are an anode material in MFCs that generate an excess of electrons and protons by biologically oxidizing substrates, such as sodium acetate or organic waste, and the flow of these electrons produces significant amounts of electricity. Recently, it was found that EABs can be used as a biogenic-reducing tool to synthesize metal nanoparticles and metal–metal oxide nanocomposites. The EAB-mediated synthesis of metal nanoparticles and metal–metal oxide nanocomposites is expected to provide a new avenue for the greener synthesis of nanomaterials with high efficiency than other synthetic procedures. It was also found that EABs could be effectively used as a tool to provide electrons and protons by biologically decomposing acetate which is later used in the presence of a suitable catalyst for the bio-hydrogen production. These nanoparticles as well as nanocomposites syntheses and bio-hydrogen production takes place in water at 30 °C and does not involve any energy input which make these approaches highly efficient. These findings show that EAB is a fascinating biogenic tool for MFCs, nanomaterials synthesis, bioremediation, and bio-hydrogen production.