Team:LZU-China/wetlab3

         We constructed a pollutant substrate(PNP) bio-sensor coupling riboflavin synthetic gene cluster, the genetically modified E.coli can secrete riboflavin when added PNP in MFC anode medium.Riboflavin is a efficient redox mediator as well as a stimulator of MFC. We created a novel MFC devices and built a quantitative monitor system of PNP via measuring voltage increment.

         When E.coli Super Seven secrete riboflavin to the anode medium or add riboflavin manually, the MFC system will have a better performance. The riboflavin is a kind of redox mediator; it could enhance the MFC power output in a great scale in just a few minute (figure 8).

Figure-9. Gradient concentrations of riboflavin could raise the MFC voltage, measured with 200Ω external resistance，peak voltages were recorded within 5 hours after riboflavin added.

We found that the most important dependent variable was not the power density or peak voltage as we think previously, instead, voltage increment value reflect riboflavin’s concentration best. Another fact was that the voltage increments were often dependent on former power output.

Measure PNP concentrations with a PNP bio-sensor coupling riboflavin MFC stimulate system.

We tried to make E.coli Super Seven co-exist with Shewanella in anode medium at the same time. When PNP pollutant was added, Super Seven could secrete riboflavin; as a result, MFC voltage would rise and reflect the PNP concentrations. Though riboflavin’s expression quantity was relative low as the iGEM authority plasmid pSB1C3 is not the best expression vector, we still found the interrelationship between PNP addition and voltage increment.

Figure-10. Using MFC devices measuring concentrations of PNP obtained a fitting curve.

We introduced(ΔE) as dependent variable, PNP concentration is independent variable and the previous stable voltage of MFC without pollutant treatment, E1, is an important parameter in this interrelationship. We also created a constant value, which dependent on our novel MFC devices and experimental data.

We conclude an empirical formula for our devices:

In our experiments with MFC devices designed by ourselves, the MFC Characteristic Constant is a certain value, C=1.4034.