The increasing stress on the environment demands new innovative technologies to satiate the growing energy needs of our society. Considering this, we have aimed to develop biogenic solar cell that can harvest energy from the sun by using genetically modified Escherichia coli. The bacteria are modified to produce pigments capable of capturing solar energy. The pigment that attracted our attention is called lycopene, which is responsible for the red colour in different fruits and vegetables, such as tomatoes and watermelons. Lycopene is also an intermediate in the production pathway of many different carotenoids, which eventually can give us a great opportunity to further expand and fine-tune the project.
In our project we chose to use E. coli as the production system as it is a well-studied organism that also produces the substrates for lycopene biosynthesis. Furthermore, we genetically-modified the E. coli cells to produce lycopene by expressing three enzymes extracted from bacteria which are extremely resistant to different types of radiation and oxidizing agents. The genes for the enzymes we introduced into E. coli are crtE, crtB and crtI, from the extremophile Deinococcus radiodurans.
As there is no “I” in team, we are happy to introduce ourselves as one big happy and very culturally diverse family comprised of 7 aspiring biologists coming from 3 different continents, 4 amazing supervisors and many more advisors that have shaped us as a group and the project throughout its very short, but intense life. And of course, our team would not be complete without our mascot, E. soli, who has been our own guiding light at the end of the iGEM tunnel with the destination set for the Giant Jamboree in Boston.
Finally, none of this would be possible not only without the right people (or bacteria) but also without having the right support system.
We used Gibson cloning to insert the genes in a series, using only one promoter to transcribe all three genes. We first cloned the crtE gene into the pBAD vector and we proceeded by inserting the second one, crtB, and the last one, crtI. The transcription of all three genes together makes the cells produce lycopene changing their color to red. So far, we have managed to produce lycopene in DH5ɑ, but we have recently found that the BL21 gold strain is better than DH5ɑ for the production of proteins.
Successful cloning and transformation have moved us to the next step of the project, which is building the physical solar cell. We used a dye-sensitized solar cell as our foundational design, wherein a conductive glass plate covered in semi-conductive bacteria and another such plate covered in graphite are clamped together and act as the anode and cathode respectively. The cathode and anode are coupled together by electrical wires and an electrolyte solution, resulting in a closed circuit.
As all members of the team study biosciences we had to find the right people to point us in the right direction for those portions of the project requiring other skill sets. While attending a conference on the current state of solar panel technology we had a great opportunity to get in contact with Norwegian experts in the field. By taking into consideration their advice regarding the design of our solar cell, especially its limitations, we were able to understand that our end product should be aimed at a niche application: providing electricity in low light conditions. In addition, we created a survey to get feedback from the general public, which confirmed that there is a market for such a solution.
Increasing public awareness of synthetic biology and GMOs has been important for us from the start of the project. Our own survey has helped us map the general knowledge people have about GMOs. As a consequence, we have particularly focused our efforts on underlining the opportunities synthetic biology provides for a more sustainable society. From the beginning of this competition, we have both been partaking in collaborations with other iGEM teams who have embraced this message and we have been initiating discussions about synthetic biology with our local outreach activities.