Cellulose Processing & CBDs
Testing the feasibility of microbial cellulose-based biosensors

The University of Edinburgh iGEM 2015 team is creating a paper-based biosensor to detect purity of and contaminants in illicit drugs. In an effort to increase the applications of the proof-of-concept biosensor, the team wanted to incorporate microbial cellulose as an alternative to paper. This could decrease the cost of the biosensor as well as making the disposal easier.

For the collaboration, the Edinburg IGEM 2015 used the BBa_K321357, which is an sfGFP fused to the cellulose binding domain CBDcex transcriptionally activated by Lacl. Since the CBDcex is attached to a fluorescence, sfGFP, the strength of the binding affinity is correlated with the absorbance level. The y-axis measures the absorbance in relative fluorescent unit while the x-axis is the time incubation. Although there is large error bar, there is a distinguishable difference between the binding affinity of the CBD onto the cellulose unprocessed and processed sheet. The high absorbance for the processed sheet indicates that the CBD binds more effectively than the unprocessed sheet. This experiment will be repeated in the near future.

By using microbial cellulose that our team provided, the University of Edinburgh team was able to check the binding affinities of a cellulose binding domain (CBD) to the cellulose to see whether microbial cellulose-based biosensors are feasible. Our bioHYDRA project involved testing processed and unprocessed cellulose, and we sent the Edinburgh team a sample of each. This allowed the Edinburgh team to see if there is an advantage to the processing for their applications, and, since our future work includes expressing CBDs on spore coats, the processed sheets will be better for our applications as well. The CBD they tested was BBa_K1321357, which is sfGFP fused to CBDcex and driven by LacI. They chose this BioBrick because it was in the distribution kit and was already well-enough characterized to ensure that the only variable they tested was whether the sheets were processed. The data they provided shows that less protein dissociation occurred from the processed sheets.

Beyond the Bench

Despite the time zone difference, we held several skype meetings throughout the summer to discuss our collaborations and get to know each other. We also got together early on during the summer, sharing our enthusiasm over IGEM and the potential collaboration between the two teams. To celebrate our collaboration, the Edinburgh team baked an IGEM cake when we had a joint party with Brooke and Liusahd in California at the beginning of the summer!