Soil-Based Microbial Fuel Cells

[Crazy_Mad_Scientist]

Hi Donna,

Thanks for the advice! I think I secured my mfc design!

Here is an overview of all the experiments and test I might do:

1. Obtain soil samples from the Fraser river and contaminated garden. Build mfc and place moistened soil in the anode. A small sample of the soil from either location will be plated on agar and colonies will be counted. The top three largest colonies may be identified via pcr if there is time.

2. Feed mfc with substrates along with a small amount of lead contaminated water throughout the whole 2-4 weeks of experimentation. (Lead concentrations will gradually be increased to encourage growth of lead-reducing bacteria.) Multimeter readings will be recorded.

3. After 2-4 weeks soil bacteria will be swabbed onto agar plates with varying concentrations of lead as to find the highest concentration where bacteria can survive. Colonies will be counted via gimp. The top three largest colonies will be identified via pcr and compared on blast if dna sequencing is performed.

4. Top 3 colonies will be grown in seperate nutrient broth tubes with the highest level of lead concentration (found in less step) with one tube containing all three colony bacteria. After 24 hours, lead concentrations will be identified using the lead kit.

Everything will be completed in about 6-7 months. 2-3 trials will be completed depending on the amount of time there is.

[donnahardy2]

Hi CMS,

You are making excellent use of your holiday. The overall plan looks very good.

I recommend making a detailed list of all materials needed for each experiment and a detailed protocol for each step as well. This will help you think about small details in advance and ensure that you have all materials available. I will post some additional comments and questions to help with the planning process.

First comment. The bacteria that can use Pb+2 as an electron receptor are probably going to be obligate anaerobes. This means that they will die if you expose them to oxygen. So, you will need a different medium to grow them.

How many MFC’s are you going to build?

Donna

[Crazy_Mad_Scientist]

Hi Donna,

Haha thank you!

I was thinking that I can quickly swab the bacteria onto petri dishes and transfer them to an anerobic chamber:

https://www.sciencebuddies.org/science- ... #procedure

This should work well with both the agar and the liquid media since the chamber would only contain around 3%-5% oxygen. For the liquid mediums, I will put the tubes into a glass jar with the match.

I am hoping to build 4 microbial fuel cells so I can conduct 2 trials simultaenously. However if heating is a problem I will only conduct 1 trial at a time. I'm not in a hurry to finish my project since I have around 5 months until district fair and 7 months until nationals (if I make it).

I will post a detailed list of all materials and steps tomorrow. By the way how often should I add the substrate solution? I've been looking everywhere to find an answer...

The two sites I found below stated that vinegar and water would make a good substrate. The second site is actually from a project at the CWSF several years ago!

http://www.wired.co.uk/article/how-to-m ... -fuel-cell

https://secure.youthscience.ca/virtualc ... &regionid=

Thank you!

CMS

[donnahardy2]

Hi CMS,

The protocol with the anaerobic chamber will work well for growing facultative anaerobic bacteria. Many of the bacteria that have been isolated from MFC's can grow anaerobically and aerobically.

Please see if you can find any information on the identify of bacteria that can reduce Pv+2. You need to find out if they prefer glucose, acetate, or perhaps butyrate as a carbon source. If you can't find any research topic, then you will have to pick one carbon source as this will be a controlled parameter.

I will look for some references also.

Donna

[donnahardy2]

Hi CMS,

Here are some references that might be useful. I need to read these carefully also.

1. Article describing growth of sulfate reducing bacteria to convert lead to insoluble lead sulfides. Optimum growth conditions include sodium lactate as a carbon source; also investigated optimum temperature, pH, and time for this application.

http://www.sciencedirect.com/science/ar ... 8107001397

2. Metal recovery using microbial fuel cells; includes examples of every metal, except Pb, but could be used as a model for your project. .

http://spot.colorado.edu/~zhre0706/pape ... Review.pdf

3.https://www.researchgate.net/publicatio ... monitoring

Donna

[Crazy_Mad_Scientist]

Hi Donna,

Unfortunately I could not find any research papers about reduction of Pb+2 in microbial fuel cells . Do you think that I should go with a mixture of acetate and glucose? I don't think that I can obtain sodium lactate from my school.

Thank you for the papers! I have read throught the majority of them. However for article 1, I could not obtain the full article. Is there another way that I can find the results to that study?

Quick question: is the compression fitting used in the science buddies tutorial a compression coupling? I visited my local hardware store and it was the closest thing that looked like it.

Thank you!

[donnahardy2]

Hi CMS,

ou are right. It is hard to find research articles on this topic.

I had based the suggestion of working on lead reduction based on the following abstract. Unfortunately, the article can only be obtained by providing personal information to the Chinese authors, which may not be a good idea.

https://www.researchgate.net/publicatio ... _Fuel_Cell

Here’s an article on using microbial fuel cells to recover heavy metals. Unfortunately, I cannot access the article, but the reference list is included that may yield information. However, I could not see any references that were specifically on Pb

http://link.springer.com/article/10.100 ... 014-0474-2

Here is a paper that describes exactly what you want to do, except with copper. The authors used a MFC to reduce copper ions to copper metal . Copper is a valuable metal so it is worthwhile to develop a recovery process using a MFC. One of the technical problems with a MFC is high resistance, so please note the specific steps the authors used to minimize resistance in their MFC. For your project, you need to do exactly the same reaction, only using Pb+2 as the electron acceptor.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4473641/

One of the additional challenges you have for a lead project is that lead is a toxic element so you will inhibit microbial growth if you use a concentration that’s too high. We need to find a reference that suggests a suitable concentration of Pb+2 to use.

I’ll keep looking.

Donna

[donnahardy2]

Hi CMS,

I had a thought about funding for your project. Ask the UBC researcher if there any source of grant money available for your project on lead removal. Ask the same question of whoever has jurisdiction over the lead-contaminated garden. You can describe your project and explain how it might help the community. You can add up the approximate cost of items that you need to purchase from your list of required materials .

I have not found a reference on using a MFC for lead recovery yet. However in the meantime, here is some more background information for your project. There are a variety of subjects that you will need to be able to explain to the science fair judges, so this will help you to prepare:

1. Electrochemistry of lead: In a microbial fuel cell, you will be measuring the flow of electrons, or current, from the anode (anaerobic chamber) of the MFC to the cathode (aerobic chamber). You need the complete circuit to be able to measure the voltage and current.

This website includes a good description of half-cell potentials and redox (reduction/oxidation) reactions.

http://chemcollective.org/chem/electroc ... tecell.php

2. Here’s an article that reviews the process for electrodeposition of lead. Lead is apparently easy to electroplate, and the reduction of Pb+2 to Pb is what you are interested in.

http://www2.bren.ucsb.edu/~dturney/port ... ing/08.pdf

The reduction of Pb+2 to Pb (0) has a reduction potential of -0.13 V. If this is paired with an oxidation reaction that generates more than 0.13 V, then electrons will flow from the anode to the cathode and you will be able to measure voltage and current, as long as the resistance is not too high.

3. Valence electrons of lead: This website has a good diagram that shows the electron configuration of lead.

http://environmentalchemistry.com/yogi/periodic/Pb.html

The element has 82 protons and 82 electrons for a net neutral charge. There are 5 electron shells that are completely filled and 4 electrons in the 6th shell. The outer 4 electrons are available for chemical reactions. (Refer to the shell model which shows a dot for each electron). These outer electrons are named 6s2 and 6p2 and they can escape from the atom through a chemical reaction called oxidation to create a lead ion that has a +2 charge (missing 2 electrons) or a +4 charge (missing 4 electrons). The molecule that receives the electrons from Pb will be reduced. Oxidation and reduction reactions always occur together.

4. Anaerobic respiration. Humans and other animals use oxygen as an electron acceptor to produce energy from food. This is called aerobic respiration. Some microbes use an element other than oxygen for an electron acceptor to produce ATP (energy) in a process called anaerobic respiration. The microbes in the anode chamber of a MFC transfer the electrons to the anode electrode and the electrons then flow to the cathode chamber.

https://en.wikipedia.org/wiki/Anaerobic_respiration

5. Solubility of lead compounds. This website shows the solubility of various lead compounds on grams/100 mL. Many lead salts have low solubility and this feature has been used to reduce the toxicity of lead in environmental samples. The traditional treatment of lead-contaminated soils is to add phosphate fertilizer, which forms insoluble lead phosphate. The authors of the one paper I found yesterday used sulfide-producing anaerobes to precipitate lead as lead sulfide.

https://en.wikipedia.org/wiki/Solubility_table

Note that lead acetate has a solubility of 44.3 grams per 100 mL at 20 degrees C compared to lead phosphate with a solubility 3.4 x 10-4 and lead sulfide at 6.76 x 10 -13, or 0.000000000000676 grams/100 mL.

Donna

[Crazy_Mad_Scientist]

Hi Donna,

The third paper was very informative! I have noted some construction aspects to avoid high resistance. By the way I am still looking for a UBC professor since there are few that work with bacteria bioremediation and mfcs. Here are some of the professors that seem knowledgable in this field:

http://www.chbe.ubc.ca/profile/susan-baldwin/

http://engineering.ok.ubc.ca/faculty/de ... berts.html

http://biochem.ubc.ca/person/lindsay-eltis/

This is a good lab I can contact if there is anything that requires sophisticated equipment:

https://navigator.innovation.ca/en/navi ... ologyGroup

I'm not too worried about expenses right now, especially since grants for students are so hard to get... Last year all of the platinum projects at the CWSF were done at home without a mentor or a lab

However if my project begins to get pricey, I can apply for the Safoni Biogenius Challenge, as they offer a $750 research grant.

Wow thanks for all the papers! I will try to finish them hopefully by tonight. I have a few projects so I will take some time off my research. I will be writing my full science fair proposal that I need to submit to my teacher tomorrow.

I think that this paper would do for lead tolerance: http://www.sid.ir/en/VEWSSID/J_pdf/80620105601.pdf

and this one: http://www.bioline.org.br/pdf?ja06032

I have a few more papers bookmarked but I haven't gotten to read them yet.

Also do you recommend that I start writing in my lab notebook now?

Thank you!

[donnahardy2]

Hi CMS,

Any of these UBC faculty members has expertise that would be helpful if they could mentor you. Here is a summary of their backgrounds. Dt. Baldwin’s and Dr. Roberts’ expertise seems more relevant for your project as they both are experts in microbiology and engineering. Dr. Ellis has expertise in molecular biology, and this would help in the second part of your project.

Susan Baldwin Bioprocess engineering, anaerobic fermentation, bioremediation. reaction kinetics
Deborah Roberts microbiology water quality engineering, treating contaminated water.
Lindsay Ellis microbiology molecular biology

I would write each researcher an e-mail message and very briefly describe your unique science project and ask for help. Ask for a referral if the person you are asking cannot help. At this point, it seems like you just need someone to review your project and make suggestions. Don’t take it personally if you don’t receive any response; professors are incredibly busy and October is grant proposal time, so they may be focused on this. However, it would be fantastic if someone could provide advice for your project
. .
I will read the papers you found and send back comments later today.

You can start writing in your notebook as soon as you make your list of materials and have your plans. Just write a few brief notes every time you do something on your project.

Donna

[donnahardy2]

Hi CMS,

The UBC lab sounds like a good resource. I wonder if they have any extra incubators available. You should also find out if Dr. Eskicioglu could provide advice for your science project.

The reference on heavy metal resistance in microorganisms has good background information, but consider this reference a poor example of data presentation. The second article has much better data presentation and includes some interesting data on microbial lead-resistance.

Donna

[Crazy_Mad_Scientist]

Hi Donna,

I was thinking that I would send them a copy of my detailed proposal to the professors if they agreed to look over it. This way I can get feedback, and maybe a lab to work in on the last part of my project (pcr and genetics).

I understand when professors don't respond to my emails . Before deciding on this idea, I sent many emails for possible mentorship. However I didn't receive any replies. However this time I'm not asking for lab space immediatly so I hope that they do reply.

I found that the microbial fuel cells I will construct will be fairly small, so I think I can build a large enough incubator at home (with a styrofoam box and lightbulb and arduino to control temperature).

I will start on a detailed methods and materials procedure:

1. Construct microbial fuel cell as described in https://www.sciencebuddies.org/science- ... p026.shtml. Soil samples will be collected 5cm below ground, and will be immediatly transferred to mfc chamber after dampening with water. Equal weights of soil will be measured in the 2 mfcs constructed. Mfcs will be immediatly incubated at 20 - 25 degrees celcius. Multimeter readings will be taken after a stable current is established (in order to show increase in voltage).

Major supplies needed: incubator, carbon cloth, aquarium pump, compression joints.

Note: a few innovations will be applied to the cells; in the anode, a tube will be attached to a bottle to deliver substrates by drip-drop. The tube will be placed next to the biofilm (where the electrode base is). Another tube will be attached to a container filled with water to remove excess gas from the anode. The whole mfc will be placed on top of a plastic container to catch leaks.

Methods to reduce internal resistance: reduce distance between electrodes, increase ion concentration in salt bridge (increase conductivity).

Agar dishes will be made with limited exposure to oxygen. Bacteria from the soil sample will be plated and stored in an anaerobic bacteria at 25 degrees celcius for 24 - 48 hours. Colonies will be counted via computer imaging software (which I plan to code). Top three biggest colonies will be identified via biochemical methods if there is time. If colonies cannot be analyzed biochemically, colony morphology and colours will be analyzed on the computer.

By the way do you recommend that I use graphite for electrodes? This study used graphite rods from HB pencils: http://www.omicsonline.org/open-access/ ... ?aid=57993

I will write the other steps in another post.

Thanks!
CMS

[donnahardy2]

Hi CMS,

I would not recommend sending out your detailed protocol unless you know there is someone who is available to review it. Do wait until you get some sort of positive response from one of the professors.

Perhaps you could call Dr. Eskicioglu’s UBC lab and ask if there is someone available who could help you. There might be a graduate student available who could help. The School of Engineering phone number is (250) 807-8544. As an introduction, perhaps you could think of one question about your project (such as what would be the best electrode material for your MFC) and start with that. If you get a positive response, you could proceed with the request for a review, and possibly, a local mentor.

A small microbial fuel cell would be perfect. You will just need to show that your concept will work. A light bulb in a Styrofoam box should be perfect for a 30 degree Centigrade incubator.

For the anode chamber you will want to use the carbon source that will allow the maximum amount of bacterial growth and an electrode with the maximum surface area. From all of the papers that we have reviewed lately, do you recall which conditions allowed for maximum power generation? That’s what you want to do. I will check the references also.

You will be converting the Pb+2 to Pb0 in the cathode chamber. Lead does not conduct electricity well, so would not be a good material for an electrode. We read one paper that used Pb02 as a cathode electrode material. I don’t know if it is possible to electroplate Pb onto graphite. This question needs to be answered before you can build your MFC.

Donna

[donnahardy2]

Hi CMS,

Anode electrode: Here is a recent reference that reviews the power generated with different anode, cathode, microbe, and substrate combinations. Let me know if you can’t access this paper. Excluding the platinum electrode, which would be cost-prohibitive, for your project, it looks like you would get good results with either a carbon paper or graphite anode electrode. The anode electrode is one of your controlled parameters, so pick the one that you can easily obtain.

ww.sciencedirect.com/science/article/pii/S1110016815000484

Substrate: It looks like sewage sludge is generally the best carbon source for MFC power generation. However, this type of sample is of unknown composition, so you should pick a carbon source with a known molecular structure. Glucose looks like a good choice, but acetate or lactate would also work. Pick one that you can obtain easily. The substrate and concentration is a controlled parameter, so make one choice.

Cathode electrode: This review article has the best description of the chemistry and requirements for the cathode chamber that we have seen. Table 3 shows good results with carbon, graphite, graphite felt, and other materials. Since you want to reduce Pb in the cathode chamber , you need to figure out how to optimize conditions so that the Pb +2 will be the final electron acceptor. You can add a soluble lead salt, such as lead acetate or lead nitrate, but you will probably also want to add a catalyst as described in the paper.

This is a 2015 reference and the author of the paper might be available to give you some advice on the composition of a cathode chamber that could be used to convert Pb+2 to Pb. Why don’t you send an e-mail message to Dr. Rahimnejad and briefly describe your project and ask for advice? His e-mail address is included in a link by his name at the top of the paper.

You should also read the sections on the cation exchange membrane (CEM) which allows transfer of the protons to the cathode chamber.

Here is another reference that used ammonia-treated carbon cloth and phosphate buffer to enhance power generation. The ammonia treatment at 700 degrees C would be outside of the scope of your project. You can file this idea away as a change you would make if you had unlimited resources. The phosphate buffer idea should be easy enough for you to do.

tps://pdfs.semanticscholar.org/a2a3/e24035e02bc0ff08b976ef1cbb74447e0317.pdf

Donna

[donnahardy2]

Hi CMS,

Going back to the copper article that you are trying to model, the authors used copper metal as the cathode electrode. This makes sense because the copper ions were electroplated onto the copper electrode.

The author of this paper says that the details of the MFC set up for copper plating are in the following reference. However, I can’t seem to find the reference cited in the paper. Can you send an e-mail message to this author also and ask for the experimental set-up reference? You can also ask for suggestions for your project. The author is Pau Rodenas Motos and the e-mail address in the Netherlands is ln.sustew@sotomsanedor.uap.

Kuntke P., Sleutels T., Saakes M., Buisman C. J. N. (2014). Hydrogen production and ammonium recovery from urine by a Microbial Electrolysis Cell. Int. J. Hydrogen Energy 394771–4778. 10.1016/j.ijhydene.2013.10.089

You should also note that these authors used acetate as the carbon source and they had to adjust the pH during the experiment.

Lead can be electroplated onto copper. I’m not sure how well It will plate onto graphite.

https://www.youtube.com/watch?v=rJocKumgFlk

Donna