Microbial Fuel Cells in Power Generation and Extended Applications - Biotechnology in China: Biofuels and Bioenergy - page 178

and robust MFC system. Since many of the exoelectrogens belong to dissimilar
metal-reducing bacteria, Wang et al. [ 65 ] proposed a rapid selection strategy for an
anodophilic consortium through serial dilution and regrowth of bacteria using
poorly crystalline Fe(III) oxide, which selectively offers a favorable environment
for anodophilic consortium growth. The MFC inoculated with this selected con-
sortium showed distinctly higher power density and CE than those with original
biofilm and activated sludge. Meanwhile, the start-up period of the MFC was also
significantly shortened. However, this method of dilution and regrowth can only
screen one major category of bacteria each time and is unsuitable for isolation of
species with low population density. Hou et al. [ 66 ] developed a microfabricated
MFC array to achieve high throughput screening of electrochemically active
microbes. The MFC array consists of 24 integrated anode and cathode chambers to
support direct and parallel comparison of bacterial activities. Moreover, the small
volume of the MFC array enabled a rapid and sensitive reaction process. Using this
array, several Shewanella strains capable of high electricity generation were
successfully identified and characterized. More recently, Chen et al. [ 28 ] managed
to build a microliter-level MFC array by using the simpler photolithography
technique, which offers more flexibility and economic benefits for the implement
of such rapid-screening technologies. Nevertheless, the available techniques for
rapid screening of exoelectrogens are still few, while the sensitivity and applicable
scope of the established screening/enrichment techniques are yet to be further
improved. It is worth mentioning that biocathode microbiology is also an impor-
tant area to be explored. In light of the high versatility of biocathodes, usually
bacteria with strong capabilities not only in electron transfer but also in catalyzing
the degradation of specific compounds are desired [ 57 ]. This also calls for the
development of efficient and reliable screening/enrichment techniques.

2.4.2 Consortia Interactions

Notwithstanding the advantages of selected pure strains for power generation
and specialized purposes, it should be recognized that a mixed culture could be
ultimately more desirable from a standpoint of practical wastewater treatment, due
to a higher flexibility, robustness and suitability for composite wastewater, and
usually higher electricity-producing performances. Therefore, an investigation into
the interactions among different consortia is highly desired. Indeed, the substantial
functional diversity of anode biofilm is closely associated with its phylogenetic
diversity. A synergistic relationship between photosynthetic bacteria and hetero-
trophic exoelectrogenic bacteria was found to exist in a self-sustained phototrophic
MFC [ 67 ]. Synergistic interactions between anode-attached and planktonic
bacteria were also recently demonstrated in an MFC for simultaneous electricity
generation and sulfide removal [ 68 ]. However, it remains unclear how these
different populations coexist and affect each other. This warrants a deeper

investigation.