Team:Harvard BioDesign/HP/Gold

Harvard BioDesign 2016

Gold

Integrating Advice from the Experts

Taking Advice from Professor Derek Lovley

While talking to Professor Derek Lovley, we learned it was important for our cell to be anaerobic; if the cell was in contact with atmospheric air, the bacteria could transfer electrons to available oxygen molecules instead of our electrode, thereby preventing the cell from producing a current. Since we were having difficulties making our 3-D printed fuel cell airtight, we began to seriously consider reviewing our strategy and ordering a commercially available fuel cell instead of producing one ourselves. By talking to Professor Lovley, we were able to integrate his advice into our experimental design for our microbial fuel cell (MFC) and find a fuel cell that is airtight.

We also asked Professor Lovley whether he had any recommendations for a bacterial species capable of degrading terephthalic acid. Although the professor did not have any specific recommendations, he had previously isolated an extremophile species of bacteria capable of surviving at low temperatures from marine sediment. This encouraged us to try thinking of locations where we could find bacteria capable of metabolizing terephthalic acid. After doing some research, we discovered that terephthalic acid was among the contaminants present in wastewater. Knowing that our PET-degrading bacteria, I. Sakaiensis originated at a recycling plant, we thought to contact labs that have discovered bacteria in wastewater treatment facilities. After hearing back from some labs we were able to obtain multiple species of acid-degrading bacteria for experiments.

Taking Advice from Professor Peter Girguis

Professor Peter Girguis' lab specializes in studying deep-sea organisms and has experience developing underwater fuel cells to function as power sources.1 When we told Girguis about our plan to use terephthalic acid to generate electricity, he immediately warned us current fuel cell technology is only capable of producing limited amounts of electricity and that we should take this to account when determining the precise application of our reactor. We had up to this point wanted to use the electricity generated by our MFC to power a floating device like the Seabin. However, our conversation with Girguis helped us grasp the impracticality of producing that much energy. What we found out we could do, though, was power an LED signal or a GPS ping, which we integrated into our final design of Plastiback. Thus, the energy produced by our MFC will help send a signal back to researchers to indicate the location of plastic in the ocean.

Looking ahead with Seabin

As mentioned in our human practices page, we discussed future collaborations with Dr. Sergio Ruiz-Halpern, Head of Science at Seabin. Because Seabin is still in development, we brainstormed possible future integrations of our sensor device with their platform. Speaking to Dr. Ruiz-Halpern, however, was also helpful for our current design and implementation of Plastiback. We confirmed that the electricity we would produce in our system would be much more valuable as a PET-detecting signal, rather than a supplementing power source for the Seabin or other oceanic device. And, while the Seabin may be too large to suck in microplastics, our system would actually work better with microplastic because they are easier to break down. Additionally, Dr. Ruiz-Halpern directed us to Parley for the Oceans, which provided us with actual sea plastic. This plastic, along with plastic collected by the Seabin, will in future work characterize the breakdown of weathered ocean plastic.

1Girguis Lab

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