Team:Korea U Seoul/Results
Results
Results
All the graphs are measured voltages of our bio-batteries. The voltages were measured by Keithley Digital Multimeter. The unit of X axis is hours measured.
1. MFC Validation
We measured the voltage that Shewanella oneidensis MR-1 produce when formate is given since MR-1 uses formate to generate electricity. As controls, we measured the voltage of the battery with E. coli BW25113 in the anode chamber, and the battery without microbes. Methylene blue was given as the mediator. The purpose of this experiment is to make sure that our battery device works as an MFC.
As you can see in the graph above, the battery with shewanella oneidensis MR-1 generated electricity while the controls did not. This indicates that out battery device works as an MFC.
2. EFC Validation
Diaphorase expressed E. coli BL21(DE3) was lysed by sonication and was applied into the anode chamber of our battery device. Methylene blue was given as the mediator. Lysed BL21(DE3) with void vector was the control. NADH was added to both batteries.
As you can see in the graph above, the battery with diaphorase showed higher voltages. This indicates that the diaphorase produced electricity. However, the voltage differences are very small. This could be due to the state of diaphorase, which was not fixed onto the electrode. Also it could be due to the components that exist in crude bacteria extract since there are many reducing or oxidizing agents in bacterial cells.
3. EMFC Operation
Our final goal was to prove that our device works as an EMFC. Shewanella oneidensis MR-1, BW25113 with displayed agar degrading enzymes, cell lysate of diaphorase expressed BL21(DE3), and cell lysate of TEV expressed BL21(DE3) was put into the anode chamber. Agar was used as the substrate. The battery device without agar was set as the control.
As you can see in the graph above, the battery with agar generated more electricity than the control. Our prototype EMFC apparently works as expected.
However, the voltage generated is not very high. This was expected due to some reasons. First, our battery device was not designed to generated high electricity. To get high yield, you need electrodes with large surface area but the electrodes of our device has small surface area since it is only a thin carbon paper with coated back. We designed our device this way for precise comparisont. Second, our added diaphorase was in free state which means the majority of the diaphorase was not doing much to generate electricity. A lot of EFC relate theses fixes diaphorase onto the electrode for higher yield, and stabilization of the enzymes.
Since we succeeded in operating the prototype EMFC we designed, our next goal is to improve electricity yield. This includes improving the battery device with better electrodes, optimizing the amount of reagents and cells in the device, and purifying enzymes to get rid of uselss cell lysate.
