Download Julie Paone 6/8/09 Mrs. Flanagan, Period 3 Science Research

Julie Paone
Mrs. Flanagan, Period 3
6/8/09
Science Research
Microbial Fuel Cell Speech
Intro: My name is Julie Paone and my project is The Effect of Various Carbohydrate Sources
Utilized in a Double Chamber Microbial Fuel Cell.
Need
America currently uses 4-5% of all the energy generated by power plants to clean wastewater.
The wastewater that’s being treated has 9.3 times more energy in it than the energy that’s
being used to treat it.
Knowledge Base
A microbial fuel cell consists of an anode, cathode, and electrolyte. The MFC is a design that is
heading towards wastewater treatment plants since they have tons of energy potential and
clean water is a demand. The microorganisms go through a process called electrogenesis to
produce this power. Microorganisms like bacteria have been proven to produce voltage. The
microorganisms go through a two-step process to create electricity. They remove the electrons
from the organic matter (oxidation). The second step sends the electrons over to the anode.
The electrons go through a circuit and to the cathode where they join with protons. This
process creates power while cleaning the wastewater. Hydrogen is another output that the
MFC is capable of. Making the cathode side anaerobic, the H’s can’t bond with the O’s and
create pure hydrogen.
Electrogenesis
Electrogenesis is the process. The electrons produced at the anode travel through a series of
respiratory enzymes in the cell and they make energy for the cell in the form of ATP. These
electrons are released into a terminal electron acceptor (TEA) which takes the electrons and
they are reduced. Some bacteria in a MFC are known to transfer electrons exogenously to a
TEA, such as a carbon rod. These are the bacteria that are called exoelectrogens that can be
used to produce power in a MFC. (Logan, 2008) b | A mediator-driven microbial fuel cell. An
electron-shuttling mediator accepts electrons from reduced cell constituents and abiotically
transfers the electrons to the anode. The reoxidized mediator can then undergo repeated
cycles of reduction and oxidation. In most instances, the cells that have been used in such fuel
cells only incompletely oxidize their organic fuels as shown.
Carbon Sources
The food source for the organisms is a key part in the functioning of the MFC. As I said before
the e. coli remove the electrons from the organic matter, which are carbohydrates. The
microorganisms just like us need fuel to survive. Then those electrons continue to be joined
with protons at the cathode. Some known carbon sources that have been used in an MFC are
yeast extract, galactose, glucose, lactose, maltose, fructose, sucrose, and starch. You can see
that there are monosaccharide’s, to polysaccharides, which may affect t he amount the
microorganisms can breakdown.
Glucose
Glucose’s composition is C6H12O6 and it is used as an energy source in most organisms, from
bacteria to humans. It is also a monosaccharide.
Fructose
Fructose is another monosaccharide and is an isomer of glucose.
Sucrose
Sucrose is a disaccharide which is made up of glucose and fructose.
Lactose
Lactose is also a disaccharide made of galactose and glucose fragments.
Starch
Starch has a large number of glucose units joined together and it’s the most important
carbohydrate in the human diet.
Construction
The construction of an MFC is very simple and also affordable, while still being efficient. The
most expensive material is the carbon paper, which is purchased off of a website that Logan
and other students have used. So its not very expensive. All of the other materials are provided
in the Science Research room like copper wires, GLX Pasco Probe,and simple E. col. The anode
and cathode is carbon paper. The containers are 2 plastic bottles from Carolina. A PVC pipe
connects the 2 bottles together and holds the PEM, which is gortex.
Literature Review 1
Choi, et al. 2007 examined the effect of carbon sources as the substrate in the microbial fuel
cell. His bacteria were Micrococcus luteus and he used 11 different carbon sources. He tested
yeast extract, galactose, glucose, lactose, maltose, mannitol, mannose, sorbitol, fructose,
sucrose, and starch. His construction was a double chamber MFC with a proton exchange
membrane.
Literature Review 2
Logan in 2005 used cystenine as the substrate in a double chamber MFC. Cystenine was tested
alone to see if it could act as a food source. The results showed that the efficiency achieved is
comparable to other substrates.
Literature Review 3
This is an equation of carbohydrates and oxygen to carbon dioxide and water through microbial
metabolism. Bennetto in 1990 stated that 1 molecule of glucose provides a maximum of 24
electrons. Here is a diagram showing the steps in an MFC.
Literature Review 4
One bacteria that has been used is Rhodopseudomonas palustri. Cell voltage and current were
used to calculate the power density (P=I/V). (Explain equation) Xing in 2008 stated that an
increase in anode surface increased the performance.
Purpose and Hypothesis
To determine whether a monosaccharide or disaccharide food source significantly affects the
amount of voltage produced by e. coli in a Microbial Fuel Cell. The null hypothesis states that
the type of food source will not significantly affect the voltage produced by bacteria. The
alternate hypothesis states that the type of food source has a significant affect on the amount
of voltage produced.
Methodology
Here is the methodology, starting with 10 trials with the microorganism being E. coli. The
control will be an MFC with e. coli and glucose as the sustrate. The variables will be an MFC
with starch, an MFC with fructose, an MFC with sucrose, and an MFC with lactose. The
procedure will start with the construction of the MFC and follow with the culturing of e. coli. A
GLX Pasco Probe will record the data and store it on a laptop. Data studios will record the
voltage and current and then both will be used in the equation to calculate power density.
Budget
The budget is very small except for the carbon paper, which can be expensive. Most of the
materials are either provided by the school, or can be easily purchased from Home Depot.
(Read off some of the materials)
Do ability
This project is completely doable since a previous experiment using an MFC has been done
before. The majority of the materials are familiar and I have a background in culturing the e.
coli. Algae has been cultured in the lab before. The data collection was previously done and the
Probe and Data studios has also been used before. All of the materials are accessible and the
construction can easily be created from tips and ideas on Logan’s website.
Bibliography
Here is the bibliography, thanks for listening. Do you have any questions?