Genetic Approaches for Improving Performance of MFCs

FIGUEROLA, E.M.; CORTÓN, E.; FIGUEREDO, F.; ERIJMAN, L.; GONZÁLEZ PABÓN, M.J.; SAAVEDRA, A.

Progress and Recent Trends in Microbial Fuel Cells

Elsevier

Lugar: Amsterdam; Año: 2018; p. 1 - 451

Over 100 years ago, a professor of botany at the University of Durham, an old and well- respected University in the northeast of England, precisely showed what most likely, was the first demonstration of a working microbial fuel cell (MFC). Potter?s [1] results were obtained by using yeast and a two-compartment cell (an internal porous cylinder, probably ceramic, inside a jar). Stacks and individual MFCs were assayed, and as quoted: ?The electrical effects are an expression of the activity of the microorganisms and are influenced by temperature, concentration of the nutrient medium, and the number of active organisms present. These effects are only found within the limits of temperature suitable to the micro- organisms and under conditions which are favorable to protoplasmic activity. The maximum voltage recorded was 0.3 to 0.5 volt, and a voltage of this order was never exceeded in any experiments undertaken with microorganisms?. Amazingly, some of the conclusions Potter obtained are still valid, yet his work was perceived at the time by the scientific community rather as a curiosity, and no advances in this area occurred for a long time.The rediscovery and proposal of novel and useful applications for MFCs and MFC-related bioelectrochemical systems (BES) began in the late 1970s [2,3]. MFC studies have since be- come a very active area of research. Yet, the possibility of applied molecular biology concepts to improve or modify the performance or use of BESs was just recently envisioned.About four decades after the first MFC was researched by Potter, and three decades after the rediscovery and beginnings of continuous work in this area, the discovery of the deoxyribonucleic acid (DNA) structure and function was made in 1953 [4]. This discovery introduced a new paradigm, and the development of thousands of new methods as well as instrumentation and knowledge later allowed modifications of genomic information har- bored by bacteria and other organisms for technological or scientific purposes. Molecular biology gave birth to genetic engineering, allowing ?cut and paste? genes from one organism to another, which was first developed by Cohen four decades ago [5]. One of the first goals aimed by using these techniques was to transform Escherichia coli bacteria by constructing plasmids carrying genes provided by other species, which can be fully functional in E. coli. Genetically modified (GM) microorganisms, plants, and animals are very common in labora- tory studies and now have technological applications in medicine (most of them patented), research, industry, and agriculture. In summary, they are indispensable to many industries.Still, some risks can be associated with the use of, release into the environment, or use as food for GM organisms. Therefore, they are strictly regulated by different governments. Methods and protocols for accomplishing genetic engineering are now standardized. A myriad of kits that allow performing most of these techniques are in any good molecular biology/genetics book. Some of these included in Section 13.9 are commercialized.The use of genetic engineering to modify known electrogenic microorganisms could be an appealing strategy to increase their performance as energy producers. To do so, the limiting step(s) must be identified, and the possibility to overcome them by adding new genes or deleting some of the already present genes or pathways in the genome should be studied. One possibility is to transform other microorganisms into electrogenic ones, by incorporating in their genome all the necessary genes. This is not trivial, given the complexity of the met- abolic pathways involved in electron transfer from and to electrodes, and the regulations that can prevent the actual use or release of GM organisms.