The UW-Madison iGEM team is working on a biofuel biosensor project for 2011. This project ultimately breaks down into several smaller projects, each described in greater detail in their respective sections: an ethanol sensor, an alkane sensor, and a directed evolution project for each sensor. We originally intended to use bacterial microcompartments (BMCs) to improve the efficacy of our sensors, however, due to time constraints the project was dropped.
Our biosensing systems are designed to produce a red fluorescent protein (RFP) in the presence of whatever they are designed to sense; in our case, either ethanol (EtOH) or n-alkanes. These two compounds are frequently used for biofuel. Currently, common laboratory chromatography techniques are used to characterize biofuel production commercially. By using biosensors, we hope to provide an accurate, cheaper, and less time-consuming method of assessing biofuel production.
We found the idea of directed evolution very promising for improving our biosensors to increase commercial applicability, and wanted to do so in a way that would utilize the parts registry. We used sacB (BBa_K322921), a kanamycin selection, and a red fluorescent protein to produce a device that can be useful for future teams to improve their own one- or two-component sensor systems. As we worked with mutant libraries of BioBrick parts, we considered how directed evolution could fit into the registry. You can see our considerations in the human practice section.
About the image: Our current system uses a two plasmid system that requires both arabinose and the desired analyte to produce RFP. Using an arabinose inducible promoter ultimately allows better control of the transcription of RFP.