Microbial energy cells

Every year, an average of 33 billion gallons of domestic wastewater must be treated preliminary before being discharged into the river. If only the electricity is calculated separately, each year the US has to spend 25 billion USD for the operation of the treatment system. That is not to mention a large amount of chemicals consumed and only US . The whole world has to deal with the risk of lack of clean water, and to solve the situation of increasing waste due to pressure. population.

Geobacter sp

The answer to these difficult problems is a technology that was born in 1962, 1963 (Sisler, Konikoff, Reynold, Harris) but has been "overslept" until recent years, when energy demand become more urgent than ever.

Application of microbial energy cells for waste treatment - A double job

"The process of decomposing organic compounds in microbial cells is always accompanied by the release of electronic energy." MCPorter (1911)

Since 1911 Porter has confirmed that the electron flow always exists with the metabolism of living organisms, which is the basis for 50 years after Sisler was the first to discover the presence of electric current when giving microorganisms. developed on graphite anode. At that time, because the current obtained was too small and the pioneers used the input stream (input fuel) as the culture medium, making this current more expensive and difficult to apply. That is why this exciting discovery soon sinks into oblivion and microbial release mechanisms of microorganisms into anode cannot be explained even though humans have been receptive to cell metabolism chains. Only in recent years, when the fossil fuel situation began to "get hot", people realized the endless source of microbial power and its practicality, many scientists began to concentrate. Research and dominate the energy source that has "overslept" this.

Some key principles:

The main principle of microbial fuel cells is that the electron flow is transferred indirectly through the interaction between the reducing product and the positive electrode. The spatial separation of the final electron acceptor reaction results in a difference in the electromotive force and the flow of electrons flowing through when we use the wire connecting the two electrodes again.

There are 3 main types of microbial energy cells:

+ Type A: Intermediate electron conductors are available in the environment.
+ Type B: Microorganisms with a special membrane protein system, capable of transferring electrons directly to the electrode.
+ Type C: Electrodes are oxidized by microorganisms to create an electron source.

Some typical systems:

+ The system of Peter Benetto (London) uses extracellular enzyme enzyme system in yeast: it is difficult to apply large scale because of the compulsory substance is Methylene blue.

+ In 2004, the University of Pennsylvania successfully created a microbial energy collection system with a bioreactor-like structure with a single cavity, continuous fuel inlet. According to this improvement, if wastewater is used as waste water, in addition to the obtained power, the concentration of dissolved organic matter decreases significantly. The DO of water is always stable because the air is continuously diffused, providing oxygen for reaction at Catot.

proton + oxygen -> water.

Bruce Logan, the father of the design, said the current difficulty in the application of microbial energy cells is that the energy generated is too small, and cannot use Platinum as an electrode for systems. great. However, according to his judgment, microbial energy cells are still the trend of the future with low cost equivalent to plant therapy in wastewater treatment.

+ The system uses the ability to transmit electrons directly to the electrode of NASA's Geobacteraceae bacteria with a true voltage of 0.5 Volt, thanks to the accompanying amplification system, Dr. Bruce Brittmann's team increased the voltage. This up to 2 Volt. Currently, NASA has applied this system to solve the crew's domestic waste problem.

Exploring the process of electron transfer to electrodes :

To explain the different discharges as well as the different discharge performance among microorganisms, different hypotheses have been proposed, such as the small area of ​​contact between electron transport protein (ETP) and the electrode. , or many species of bacteria (such as E. coli, Pseudomonas, Proteus, Bacillus .) are unable to transfer electrons in external intracellular reactions .

In the first studies of microbial energy cells, it was hypothesized that the discharge process occurred by electron transport proteins on the membrane.

The most recent discovery on energy cells is the mechanism of electron transfer from the end-to-end electron to the last electronic receptor - a complex that takes electrons out of the cell instead of as we know it, the whole antiparticle. The application takes place inside the cell, on the membrane or in the cyclic space.

Research has shown that iron reduction of Geobacter sulfurreducens occurs on pili of bacteria with the atoms of Fe (III) on the pili head. The cell and pili itself are like a pair of electrodes, so it is found that the electron transfer process in Geobacteraceae is much more effective than other bacteria.

In addition to Geobacter, a number of other potential bacteria in this area are Rhodoferax ferrireducens, Shewanella putrefaciens, Aeromonas hydrophila, Desulfomonas sp . in which Geobacter sulfurreducens and Shewanella putrefaciens are emerging especially because of their ability to use the source. diverse substrates, most suitable for the production of electricity from waste.

The results of the Nature rev 2006 study are an important finding in the mechanism of electron transfer, which realizes the ability to transform microbial energy cells into practice. However, another problem that is highly appreciated here is the research environment, a model tool for studying electric currents in bacteria.

References:

[1] Derek R. Lovrey. Bug juice: harvesting electricity with microorganisms. Nature Rev. 4, 497-508 (July 2006)
[2] Article: NASA-supported people are working to develop a fuel fuel that can extract electricity from human waste.
[3] Fuel-cell Microbes' Double Duty: Treat Water, Make Energy. Science daily. (2004)
[4] Bacteria Convert Food Processing Waste To Hydrogen. Science daily. (2003)
[5] Mario Jardon. Microbial fuel cells from Rhodoferax ferrireducens (2003)

Nguyen Huu Hoang