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Team:Lyon-INSA/BiofilmK
From 2012.igem.org
The INSA-Lyon iGEM 2012 solution: “Biofilm Killer”
Biological solutions presented above are very interesting and promising. But synthetic biology could make them even more powerful by providing a technology:
- able to control, prevent and protect industrial equipment
- using non-persistent molecules in the environment
- minimizing harm to individual, products and environment
To meet these challenges, we have chosen to build a bacterial strain based on the environmental friendly Bacillus subtilis strain (already used to feed animals and promote healthy vegetable growth. “Biofilm Killer” was engineered to both destroy and then replace, if needed, the deleterious contamination by a positive biofilm. Our solution is based on 3 genetic modules:
- KILL and SCATTER the biofilm. The effect of the biocide and scattering agents produced by the bacteria can be enhanced by the “torpedo” behavior of the Bacillus swimmers.
- COAT the surface with a surfactant reagent in presence of the inducteur 1 (xylose).
- STICK to install a positif biofilm in presence of the inducteur 2 (IPTG).
Estimating the cost of the current industrial solutions
A first company that accept to answer our questions estimated that, considering the use of chemical reagents (€50 per use : 3 kg of cleaning products, €15 of disinfectants) and of a sterilizing filter to recover biological debris (€100 to €300 per use depending on its size), the total cost of a 4 hour wash of a 1000L tank was from €165 to €365 ($215 to $475)per sterilization.
The second one indicated a €480 ($625) cost estimation for a 1500L tank per sterilization.
Such estimations made us confident on the competitive potential of our bacteria, considering the low cost of their growth. The only thing left to be done was then to prove it by estimating the cost of our own solution.
Biofilm Killer implementation : a viable solution
We extrapolated both our results in 96 microwells plates, which showed us the optimal effective concentration of cells for a given surface (2,5.108 cells for a growth area of 0.34 cm² covered by S. aureus), and the market prices for genetically modified Bacillus subtilis freeze-dryed cells to the 1000L tank and 20m pipes of Gattefossé. We used two different prices in our calculations : the average price ($5,55 / kg) and the highest price ($9,58 / kg).
In the end, we estimated that the bacterial cost of the sterilization of a "Gattefossé tank" would be $0,3 per use in the first case and $0,5 per use in the second one. However, because of safety precautions, we would also need the 0,2 µm filters they used to confine our biological waste, so that the global price would be increased by at least $100. We also developped a sterilization protocol for this tank (see below) :
Besides, we generalized our biological prices in relation to a 1 m² surface to sterilize : it would then be $0,06 / m² for the average price and $0,1 / m² for the highest one.
Eventually, we thought of a packaging for our product : we would use 25 kg bags of freeze-dried cells (as it is actually done in the market) we would sell $12,25 (FOB price), which is the highest one (of course !).
Main advantages
Lower cost : No need to have a protein purification step which is very expensive.
Eco-friendly: “Biofilm Killer” won’t release toxic chemicals in the environment since the proteins used can be easily destroyed.
The “biological swiss-knife”: “Biofilm Killer” should be able to replace mechanical cleaning actions thanks to the swarming properties of our strain which can penetrate deep inside the biofilm and release the active molecules in situ all over the biofilm.
