iGEM Team Aachen 2017

Our Achievements

With the development and realization of Salt Vaults, yeasts capable of taking up and storing sodium, chloride and potassium, we rethought wastewater treatment – ok, we started.

1st Creation of VAULTer, a yeast mutant taking up 5x more NaCl than the native wildtype, sequestrating 39% (6g/L) of the NaCl of a media containing 0.6 M NaCl (equal to seawater salinization).

2nd Development of microbial supercollectors capable of sequestrating various ions, successfully demonstrated with sodium and potassium.

3rd Creation of yeasts with increased halotolerance in comparison to wildtype.

4th Ultrafiltration as a convenient method to separate yeast and water, and hinder the Salt Vaults from spreading into the environment

5th Initiation of political debate on genetic engineering in Germany

6th Modelling of the ion pathways in modified yeast

7th Assembly and submission of a tested and functional BioBrick

8th Development of an affordable peristaltic pump, which can be used by further iGEM Teams

We are proud on our achievements and success, however work just started. This outlook gives you information on possible developments to be investigated in future.

1st Integration and overexpression of NaCl-transporters

We identified and worked on the most important NaCl transporting proteins: efflux mechanisms, pyro-phosphatases for a higher proton gradient and vacuolar uptake transporters. Our results showed that only some of them have positive effect on ion-uptake. NHA1, for example, identified to be an efflux transporter, had a negative impact on corresponding mutants. A possible reason for this are complex interactions within the cellular ion-household or surcharge of the cells. New combinations of transporters and integration of new transporters, not only from Arabidopsis thaliana, could further enhance the vacuolar ion uptake of NaCl. NHX1, for example, showed positive results in all mutants. A combination of ATAVENA, the most successful mutant, with NHX1 is therefore highly interesting.

Graphic der Ionenuptakes

2nd Integration of chloride transporters

We initially planned to integrate chloride import mechanisms, working analogous to the sodium uptake, into our Salt Vaults. However, our mutants show both enhanced sodium and chloride uptake, indicating parallel influx of sodium and chloride, if the uptake of one of them is enhanced. It is interesting to test the impact of integrating both sodium and chloride transporters into one mutant ant test the effects on ion uptake.

3rd Realization of the vision of microbial supercollectors

We have proven vacuolar uptake of Salt Vaults for sodium, chloride and potassium. Cooperations with industrial and municipal wastewater treatment reveled the need for the separation of water from many more pollutants: ions, heavy metals, organic molecules. Besides potassium we tried to initiate sulfate uptake by integrating plant import mechanisms into yeast. While succeeding with potassium, we were not able to finish and prove enhanced sulphate uptake due to shortage of time.

The vacuolar uptake of a wide range of pollutants using yeast is an efficient and new application for wastewater treatment. Basically, every substance could be specifically sequenstrated by using the advantage of biological systems to be highly specific for substrates. Every known import mechanism could be integrated into yeast to access a new kind of pollutant. Within our research, we have for example, identified plant or yeast uptake mechanisms for sulphate, phosphate or heavy metals.

In future, protein engineering reveals a whole new range of pollutants to be taken up by yeast. Using protein engineering the design of novel transporters with new active sites, specific for new kinds of substances, could be enabled.

4th New applications

Developing uptake mechanisms for new pollutants extends the fields of applications drastically. Industrial wastewater treatment is and will be the most obvious application in future. In this application, new mutants could purify waters from all kinds of toxic substances. But there are alternative fields of applications. Using the specifity of its uptake mechanisms, the yeast could be used for every application in which specific molecules must be isolated. Examples are the recovery of catalyzing metals used for industrial processes or bio-mining, the biological exploitation of heavy metals from ores.

5th Yeast as a model organism

For our project, we chose yeast as our preferred biological system because of the native ability of yeast to sequestrate different molecules in its vacuole and resist huge osmotic pressure. The system of storing salts in the vacuole may be implemented for other organisms. Our far-reaching aim is to transfer our system to an algae species. Algae own a vacuole to accumulate salts and do not rely on an external carbon source, due to their ability to run photosynthesis. Transferring our system to these algae cells would create a biological desalination system which not only is independent of external carbon sources but also reduces the carbon-dioxide concentration in its environment.

6th Applied Design

During our project, we have put high efforts into the design of an application of our yeast within wastewater treatment and found answers on the separation, nutrition and after-usage of the yeast. However, this is a bottomless pit. Further research on nutrition and after-usage of the yeast has to done. We provided first ideas to reuse the yeast for enhanced energy-production in fouling towers, however, the realistic implementation should be further researched. To make a realistic approach on the application in water treatment, pilot plants are needed. Our work in small scale just proves the system to work.