Future of our Filtration System
How can we deal with the waste associated with our filtration system?
We had preliminary discussions with an employee from BQE Water, a water treatment company specializing in providing innovative wastewater treatment solutions to the global mining industry. They suggested that it was important to consider the fate of the metal ions following binding to the pilus. After use of our metal binding reactor, we would be left with a metal bearing biosolid containing both metal and bacteria. BQE Water suggested that we could mix these biosolids with anaerobic digesters that deal with municipal water treatment biosludge. Alternatively we could apply different solution conditions to the biosolids and then desorb the metal in a more concentrated form.
We researched the potential to wash our bacteria with Ethylenediaminetetraacetic acid (EDTA). EDTA is a chemical commonly used for both industrial and medical purposes from fertilisers to shampoo. EDTA can be bought as a disodium salt and will react with other metals in solution. EDTA is a very potent metal-chelating agent and the metal ions bound to our binding proteins may preferentially bind to the EDTA and so be transferred into an EDTA complex (Nyborg, 2004). Metals bound to EDTA are commonly used for purposes ranging from bleaching (in the case of cadmium disodium edetate) to fertiliser (in the case of iron disodium edetate and many others). Therefore, by washing our bacteria with EDTA after use, our filtration system could produce useful products which can be sold to mitigate the costs of running the filter.
To assess the suitability of EDTA in our project, we will carry out future experiments to test the success of EDTA's removal of metal ions from the metal binding proteins we have inserted on our modified pili.
Will our E. coli be resistant to the low PH of contaminated mine water?
Through our field trip to the Wheal Maid mine site we became aware of quite how acidic the polluted mine water we aim to filter is. The water at that site had a PH of 3. We are aware of that our genetically modified E. coli may not be resistant to such acidic water. However, whilst our choice of E.coli gave us the ability to show the proof of concept, it does not necessarily need to be the chassis organism in the future. It may be beneficial to use this concept in a more resistant organism.
On speaking to representatives from Greenpeace, it was suggested to use to look into the bacteria that live in the reed beds at the Veolia mine site as these are clearly resistant to the highly acidic water. For example: Pseudomonas azotoformans, Pantoea agglomerans could be used as an alternative.
How are we going to ensure that our product takes into account biosecurity measures?
Our experiments into the effectiveness of UV radiation as a bactericide showed that it was not suitable for use in our filtration system. This was due to two reasons. Firstly it took over 10 minutes to see a significant reduction in the population of E. coli, these findings were confirmed by a collaboration with Cardiff University iGEM team. Secondly at a lecture we attended at the iGEM UK meet up, it was stated that the escape frequency allowed by industry was 10-6 The results we obtained demonstrated that the UV was not powerful enough to reach anywhere near this standard.
Nyborg J.K. and Peersen O.B., (2004), That zincing feeling: the effects of EDTA on the behavioour of zinc-binding transcriptional regulators