Our solution capitalizes on difference between how simple and complex sugars cause the hyperglycemic spikes. Simple sugars cause a larger fluctuation in blood glucose, whether it be a sharper spike or even a depression below the homeostatic level, whereas complex sugars do not cause such a large fluctuation, thereby mitigating the spike and lessening the threat to the human body. Our solution involves engineering a genetically modified E.coli organism into the small intestine of a human where it can hydrolyze simple sugars into complex sugars, thereby mitigating hyperglycemic spikes that occur immediately after meals. Specifically, we studied the mitigation of two simple sugars, fructose and glucose, which constitute a majority of the average American diet in this research. This solution requires two different BioBricks, a polymerization circuit and an uptake circuit. The uptake circuit, containing the Enzyme-IIA membrane protein, transports glucose into the cytoplasm of the E.coli. The uptake circuit contains the GlgC gene, which codes for BLAH BLAH enzyme, that polymerizes glucose into glycogen. The same circuit contains the SacB gene, which codes for the levansucrase enzyme that hydrolyzes fructose into levan. Levansucrase also confers a fructose sensitivity to the chassis that causes it to lyse after two hours in the presence of 5% sucrose. This releases the hydrolyzed sugars into the small intestine where they are broken down slowly and absorbed into the body, thereby mitigating the hyperglycemic spike. Synthetic biology is a better solution than existing chemicals, such as alpha-glucosidase inhibitors and analogs of amylin, that perform the same hydrolyses because a bacterium does not require dosage and can easily adapt to variable concentrations of simple sugars present. Therefore, the difficulties of dosage that remain a problem with drugs are not an issue with the bacteria. Limitations of this solution are mild gastrointestinal symptoms that already exist with chemical solutions due to the similar nature of treatment. Furthermore, the introduction of a probiotic into the body poses a risk of infection or gene transfer into other bacteria of the gut. However, the preferred strain of the E.coli chassis would be a probiotic-certified bacteria that would be biologically harnessed from colonizing the gut or performing horizontal gene transfer.

Glucose and fructose are uptaken by different mechanisms into E.coli due to the nature of their polymerization. Glucose, polymerized into glycogen in the cytoplasm, requires to be transferred through the two outer membranes of E.coli. Glucose can diffuse through the outer membrane but requires the use of the Enzyme-IIA to pump it through the inner membrane to the cytoplasm. On the other hand, the levansucrase enzyme polymerizes fructose into levan between the two membranes of E.coli. Fructose, which easily dissolves through the outer membrane but is impermeable to the inner membrane, does not require a protein to transport it to the space between the two membranes where the levansucrase enzyme exists. Therefore, the sugar uptake cassette is only the Enzyme-IIA.

The polymerization plasmid consists of the GlgC gene, which encodes for the protein BLAH that polymerizes glucose into glycogen, and the SacB gene, which encodes for the levansucrase protein that polymerizes fructose to levan and confers levan sensitivity to the chassis in the presence of 5% fructose.

The uniqueness of this kill switch originates from the fact that it is not genetically based and instead relies on the toxic effect of fructose to the chassis. This type of kill-switch better serves our purpose because there is lessened risk of a genetic mutation in the kill-switch gene erasing the kill switch capability. It is less likely that mutations will erase the toxic effects of fructose on E.coli due to the SacB gene.