Team:UTArlingtonTexasUSA/Design
DESIGN
In order to facilitate our project, our team has designed a special modular shape microbial fuel cell. The fuel cell is made out of acrylic glass and was specially cut and engraved for us in our university's 3D-Printing FabLab. The cell is made out of a series of six connected and sealed glass plates that contains two chambers for the anode and cathode. The glass plates used were cut as flat squares that were made using a water-tight sealant as to contain the cells inserted. In addition, the two chambers were connected using an original 3-D printed salt bridge made out of acrylonitrile butadiene styrene. The square outlined salt bridge uses a square pattern on the sides to allow the bridge to be filled up with an agar solution to be used as a permeable membrane to which the anode and cathode can contact. Finally the electrodes used in the device were carbon cloth pieces and connected to an Arduino to measure the potential across the microbial fuel cell created by the mediators in the solution. For easy maintenance and fabrication, we have used a simple and portable design so that it could be convenient to use and available for mobile operations of future experiments.
Genetically engineered microorganisms based on fusing of receptor and/or reporter proteins to an inducible gene promoter have been widely applied to detect specific environmental pollutants. Through our design we hope to offer potential for permanent and long-term monitoring of environmental pollutants through biosensing with MFC’s. This is the gene sequence we designed which was inspired by the 2007 Glasgow team’s project. The first portion of the gene (Promoter RBS XylR RBS and GFP) utilizes a constitutive promoter for continuous production of XylR transcription factor and GFP reporter are continuous. The XylR is the gene responsible for producing the detection protein (XylR), this protein serves as a transcription factor to recruit RNA polymerase binding to the Pu promoter to facilitate transcription of the pyocyanine metabolism genes (PhzS and PhzM) and mCherry reporter. The use of the fluorescent reporters are intended to allow for direct observation of the gene activation in the system and serve to calibrate the sensor.
In order to carry out this project, our team has designed a special modular shape microbial fuel cell. The fuel cell is made out of acrylic plexiglass and was specially cut and engraved for our use. The cell is made out of a series of six connected and sealed plexiglass plates that contains two chambers for the anode and cathode. The plexiglass plates used were cut as flat squares that were made using a water-tight sealant as to contain the cells inserted. In addition, the two chambers were connected using an original 3-D printed salt bridge made out of acrylonitrile butadiene styrene. The square outlined salt bridge uses a hexagon pattern on the sides to allow the bridge to be filled up with an agar solution to be used as a permeable membrane to which the anode and cathode can contact. Finally the electrodes used in the device were carbon cloth pieces connected to an Arduino to measure the potential across the microbial fuel cell created by the mediators in the solution. For easy maintenance and fabrication, we have used a simple and portable design so that it could be convenient to use and available for mobile operations of future experiments.
After the construction of the MFC, we simulated the baseline methodology by utilizing methylene-blue as a mediator in conjunction with ferricyanide as an electron acceptor to ensure that a current could be measured. We obtained a current of 1.5 mA and this measurement allowed us to confirm that the construction of the MFC was capable of supporting whether the hypothesized gene sequence could be accurately tested and implemented for the detection of xylene. The first portion of the gene are constitutive and are always on, so the bacteria continuously is producing the protein of interest, XylR. This protein initiates a cascade that activates the Pu promoter and a fluorescent mCherry.
