Team:NCKU Tainan/Measurement
Measurement
BioBrick
BBa_K381001 was first used by team BCCS-Bristol in iGEM 2010. This part encodes nitrate and nitrite sensitive promoter PyeaR with a GFP coding device and B0030 to create a nitrate-sensitive system which signals through expression of GFP. In 2010, the team BCCS-Bristol used it to sense the nitrate concentration in soil. Yet, our team think this part can do more than that. This year, our team decided to create a whole new measurement system for sensing the nitrate level in aquaculture water by using this part.
How dose it work ? Lyophilized E. coli powder ?
The nitrate in water will activate PyeaR promoter and lead to expression of GFP. We realize that liquid broth E. coli doesn’t work well in this system, having to wait for a long-time period to get the value, which is not accepted by fish farmers because a sudden increase of nitrate level will lead to the dead of the whole pool in an instant. Therefore, instead of liquid broth, we choose lyophilized E. coli powder as our platform. When water pumped into the cuvette, activity of lyophilized E. coli recovered and showed corresponding fluorescence intensity along with different nitrate level in merely 20 minutes. Comparing to 4 hours detection time in broth process, the time cost of lyophilized E. coli powder decreases dramatically.
Figure 1 . The lyophilized E. coli powder
Nitrate Sensor
The BioBrick alone is not enough to create a fully functional measurement system, a sensing device is also one of the key element to perfect the system. After doing some research, we self-assembled a portable GFP sensing device.
Figure 2 . Our idea of sensing the GFP expressed by the lyophilized E. coli powder
The Mechanism
The value of fluorescence is detected by our sensing device and recorded as voltage form. By cross-matching our data base and modelling results with voltage signal detected by device, we can evaluate the nitrate level in water accurately to 1 ppm interval. In a relatively short time period, 20 minutes , our users are able to know the nitrate level of the pond via our app.
Figure 3 . The look of our sensing system when sensing the GFP expressed by the lyophilized E. coli powder.
Advantages
Compared with the spectrophotometer in the lab, our sensing device is smaller, more portable and less energy consumed. Incorporating our data base with modelling result, we can assure the sensitivity and accuracy of our nitrate sensor. Last but not least, due to the portability of the sensing device and storability of the lyophilized E. coli powder, this method has a lot of potential to be commercialized.
