Current Advances and Applications of Microbial Biofuel Cells

Microbial biofuel cell (MBFC) technology has an immense potential, and will emerge gradually as an essential element for renewable power generations, wastewater treatment process, fuel batteries for automobile, self-powered medical implants and environment sensors, bioremediation and many more applications. In a MBFC, microbes/enzymes are used as a catalyst to convert chemical energy, available in a bioconvertible substrate, directly into electricity. The main focus of MBFC research is on the study of microbe/enzyme, the substrate and the mediator. Escherichia coli, Nocardia, Pseudomonas methanica, Clostridium butyricum, Lactobacillus plantarum, Streptococcus lactis, Erwinia dissolvens, Proteus vulgaris, Bacillus subtilis, Alcaligenes eutrophus, Enterobacter aerogenes and Desulfovibrio desulfuricans microbes have been widely used in MBFCs. Carbohydrates (glucose, sucrose, cellulose, starch), volatile fatty acids (formate, acetate, butyrate), alcohols (ethanol, methanol), amino acids, proteins and sulphides or acid mine drainages have been used as energy source (substrates) and methylene blue (MB), 2-hydroxy-l,4-naphthoquinone (HNQ), Thionine (TH), Meldola's blue (MelB) and neutral red (NR) have been used as mediators. Today, the major problems before MBFC research are short active lifetimes, low power densities, low efficiency to engineer optimal functioning of microbes, electron transport between the microbes and the current collector, multi-microbe systems and standardised characterisation protocols. In this paper, an effort has been made to compile the R and D outcome of large number of researchers on different microbes, substrates and mediators being investigated in the last five decades.