Taking Advice from Professor Derek Lovley
Professor Lovley provided many pieces of advice for our microbial fuel cell design. For example, we learned from him that 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. During our investigation of using a 3-D printed MFC, we had difficulties making our 3-D printed fuel cell airtight. After talking to Professor Lovley, 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 MFC and find a fuel cell that is airtight.
We also asked Professor Lovley whether he had any recommendations for a bacteria species capable of degrading terephthalic acid. Although he 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 is a wastewater contaminant. Knowing that our PET 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, including the bacteria used in our final MFC design, D. tsuruhatensis.
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 that fuel cells are 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 propeller system on the device. 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 the Plastiback device.
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 only projected possible integrations with their platform; however speaking to Dr. Ruiz-Halpern was helpful for our design and implementation of Plastiback. We were able to determine that the electricity we 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, could lead to future directions in characterizing the breakdown of weathered ocean plastic.