Water Colicin Cleaner: disinfected water by E. coli

We have designed and implemented a biological alternative for the disinfection of contaminated water.

We demonstrate the antimicrobial effectiveness of colicin G, colicin H and microcin C51. These proteins are produced and used naturally by the bacteria to compete with related bacteria killing them in a specific way.

Lysed bacteria (blue areas) upon addition of bacteriocin over an enterobacteria lawn

Polypeptides activity is dependent on three-dimensional structure, based on it, we want to control their activity by changing the pH of the water, for this reason, we have work on the cyanobacterium Synechocystis sp. PCC6803, which is capable of altering the pH as a result of its growth and proliferation on carbon dioxide and light. On top of this, we have performed this on a low-cost photobiorreactor.

pH change upon activation and inactivation of light due to the activity of the cyanobacteria

In order to eliminate pathogenic bacteria from contaminated water, we have designed a system of pipes, membranes and pumps using our engineering knowledge, allowing effectively and safely contaminated water disinfection.

Furthemore, we have modelled all these behaviours so to have insight on what variables are relevant and which were less important. Last, but not least, we have taken big amount of time to think, reflect and conclude about Human Practices issues regarding our project and similar ones that may look harmful for society.

Project description

As you can see in the above animation, the prototype is split into two different functional devices, each one with a different culture inside a flask over a stirrer and the final part, a vessel that contains the water that has to be purified:

1. Bacteriocin production system

In this compartment, genetically modified E. coli produce a specific bacteriocin. After some time of protein expression, the entire culture medium, including the bacterias, is driven by a peristaltic pump into the Module of Bacteriocin Separation (MoBS). Once there, flow is separated into two; most of it returns back to the original flask and a small amount of water goes through the ultrafiltration membrane. This permeate liquid is rich in bacteriocins and other small molecules that have gone through the membrane, where bacterias and other big molecules are not able to pass through the pores.

After the membrane, the filtered stream falls down through a small plastic funnel into the container that is full of contaminated water that needs to be disinfected.

2. pH stat

The aim of this part, the controller of pH (CopH), is to regulate the pH during the disinfection process to ensure that peptides only work at the desired moment. For this, we use cyanobacteria that are able to raise pH when they are illuminated and therefore growing on CO₂. pH can reach high values (around 9) which inhibit the peptides activity. After some time under the absence of light these cells can modify pH back to previous values. In other words, once there are enough peptides in the E. coli growth container to wipe out the target pathogen culture we can modify pH to activate the peptides and start disinfection. The transient of protons to the final vessel is carried out by a dialysis membrane which keeps the cyanobacteria separated from the rest of the set-up.

3. Drink vessel

It is the vessel containing the water with pathogens, where bacteriocins end up. Wait some time and you will get your clean water!

We encourage you to know more about this exciting project browsing through the different parts.