[DIYbio] Re: Perth (Australia) Group

Hi Steve.
Good to meet everybody tonight. I think we may have the start of something.

Here is the write up on making microbial fuel cells. My students did this in 2012, and we got detectable voltage and current. I reckon it would be great to throw this out to the community, not just in Perth but around the globe to see if we can find some good isolates. Maybe we could organise a competition/challenge?

So How is this for an idea to kick off our new group:

Grab a sample of mud, or soil, or even sand that exists near the interface of an aerobic to anaerobic zone, and see who can get the best power out of a microbial fuel cell.


Details on making one are cut and pasted from an article I submitted to Helix, a few years back (minus photos, to be nice on diybio!).

All aerobic organisms gain the majority of their cellular energy from the movement of high energy electron carriers through their electron transport chains. In humans, as in other animals and plants, this occurs through the electron transport chain located on the inner mitochondrial membrane. In bacteria and other prokaryotic organisms (prokaryotic = cells without a nucleus), it occurs on their cell membrane. There is a lot of interest in finding ways to intercept these high energy electron carriers and using their energy to force electrons through an external circuit^1,2. In other words, it is possible to make a battery out of bacteria, or more precisely, a fuel cell. Fuel cells differ from batteries in that they never go flat, so long as they are continuously fed with a source of chemical energy.  It is remarkably easy to make a simple fuel cell, using only mud, graphite art pens, wire, and a source of cellulose such as tissue paper. This makes the activity very suitable for a science extension or specialist class, or any class with an integrated STEM focus.

Activity: Stealing electrons from bacteria: making a microbial fuel cell.
Our extension students researched and made a microbial fuel cell, then visited Murdoch University to see a lab where such cells were being researched.

 

 

Figure 1 Construction of a microbial fuel cell

To Do

Step 1: Collect a polystyrene cup, two 6B graphite art blocks (Koh-i-Noor, www.koh-i-noor.eu, or similar), 2 lengths of 20cm insulated copper wire("old ethernet wire"), and silicone.

Step 2: Prepare the electrodes: Drill a small hole with a pin or pcb drill into the graphite. Strip some wire to make approximately 2cm of wire bare. Bend the bare wire end over so that it presses against the hole you drilled in the graphite and makes good electrical contact. Cover the bare wire joint, and the end of the graphite rod with silicone, and allow to dry for 24h. You may optionally attach a tube and a syringe connector to the electrode so that you can feed the microbes on it with other substances such as sugar.(Diabetic students (or staff !) with insulin pumps are great sources of this type of syringe connector!) (Fuel Cell Figure 1)


Step 3: Place one electrode on the bottom of the polystyrene cup and completely cover with creek mud, mixed with a small amount of torn up tissue paper (food for the microbes). You should have approximately the bottom quarter of the cup covered with mud and paper. (fuel Cell Figure 2)

Step 4: Gently fill the cup up with creek water. Place the other electrode and wire into the cup. Don't let the two electrodes touch!

Step 5: Connect a sensitive micro-ammeter (eg a multimeter set to read microamps) to measure the current flow between the two electrodes. It wont be much! It also is likely to decrease while you are measuring it. How does it change over time? What is the potential difference (voltage) between the two electrodes? (Fuel Cell Figure 3)

Possible extensions

Do the cells produce different amounts of energy when they are fed different types of chemicals (eg sucrose versus glucose vesus acetate?)

It is known (R. Cord, pers comm.) that if you "train" the microbial fuel cell by slowly decreasing the resistance of the external circuit, it becomes capable of producing more energy. What visible changes at the electrode surface accompany this? Can you selectively grow organisms that conduct electricity? It is known that such organisms may be important in some sediment communities³.

Can you design a more efficient fuel cell (the one you just made was very weak!)?. Think about flow rates, surface area, and oxygen transport.

Finally, here we all are at Murdoch University, in the lab of Dr Cord, looking at his fuel cells!

 

 

References

1.       Tweed, K (2012) http://www.scientificamerican.com/article/microbial-fuel-cell-treats-wastewater-harvests-energy/  accessed 16/07/2014

2.       Connolly, N; Yecha, P; Beyenal, H; Lantz, B; & Dewan, D (2009) http://voiland.wsu.edu/modules/2009/introduction_to_sediment.doc  accessed 16/07/2014

3.       Stromberg, J (2012) http://www.smithsonianmag.com/science-nature/live-wires-newly-discovered-seafloor-bacteria-conduct-electricity-92123933/ accessed 16/07/2014

 

On Tuesday, December 29, 2015 at 4:07:17 PM UTC+8, BigSteve wrote:

We a are on the big couches out the back. Of Clancy's Fish Pub, Fremantle. Will be here till 7ish.