Our team has designed a reactor model to carry out the starch production process at industrial level. We intend it to be a simple and easy system to be installed in different companies so that they can take advantage of their vegetable waste. In the upper cabin the substrates and bacteria will be introduced. On the other hand, in the lower cabin, after the production process, we could take out the starch.

The expression cassette relating to the bglX gene, coding for the beta-glucosidase enzyme, BBa_K523002, from the Edinburgh 2011 team, has been improved. The modification carried out is the elimination of the RBS contained in this part, and the addition of a glucose repressible promoter, BBa_K118011, as well as a strong RBS, BBa_B0030, and a double terminator, BBa_B0015. These modifications have been made with the aim of making a gene regulatory mechanism based on glucose concentrations, to finally obtain our final product, starch.

Our mathematical model allowed us to know how our system was going to evolve following differential equations of how different parameters varied as a function of time (glucoses, cellulases, synthases, repressors, celluloses, bacterias). We assumed that bacterial growth follows a logistic equation with linear dependence on the glucose concentration in the medium and that cellulose input was continuous in our system.

With this model we can play with the initial concentrations to see how the system evolves and thus be able to extrapolate these data when the experiment is performed in the proposed bioreactor.

The generation of graphs allowed us to see the behavior we hypothesized in our experiment: the concentration of bacteria increases as the glucose in the medium increases up to a certain point, the cellulases start with a high concentration and as they release glucose they decrease their concentration in the system, the synthases start to increase their concentration as the concentration of glucose in the medium increases, and the concentration of repressor decreases as the concentration of cellulases, since this fact allows the activation of the synthases.

We also leave our R programming script so that future iGEM participants can use it for their projects. One of the improvement options is to modify the strengths of the different promoters.