Team:BGU-Israel/Implementation
Design
Introduction
It was important for us that our project design was on the one hand as simple and elegant as possible, and on the other hand innovative and creative. To effectively solve the sewage fatbergs problem, we needed a system that could be performed in a highly diverse environment, which is the sewer system. Additionally, it had to be accepted by the local government as a reliable and safe method to use. This eventually pushed us in the direction of looking into Integrative and conjugative elements (ICE) system.
There are two main types of wet wipes available today in the market: The first is synthetic fibers’ wipes (made of polyester). The second type, which is also the type we chose to focus on, is of natural cellulose wipes (made of cellulose fibers).
Background
There are many issues associated with developing a fatbergs’ degradation system. The method has to be effective, affordable, and viable to perform within existing infrastructure, and limited amount of time.
The reason we chose focusing on the cellulose fibered wipes, is due the fact that cellulose already exists in nature, and hence there are already enzymes that are able to degrade this polymer. Aiming to degrade cellulose (as oppose to polyester), is possible during the period of time we had for this project.
Most of the current biological solutions that were suggested for the fatbergs problem were focusing on degrading the fats that hold the wipes create the fatbergs together, and thus preventing the problem after it has already occurred. We focused more on the wipe itself, and chose to prevent the occurrence of the fatbergs up from the very beginning of its creation.
Design
Our main experimental goal was to engineer bacteria that would be able to degrade cellulose, by displaying cellulose degrading enzymes on its membrane. In addition, we aimed to scatter this ability among the bacteria community which already exists in the drain. Eventually, we aimed to achieve an “automated” wet wipes degradation system based on bacteria power in the sewer system. In order to achieve that goal, we decided to combine two paths:
- Constructing a cellulose degrading bacteria using cellulase, CBD and AIDA-I.
- Spreading cellulose degrading quality among bacteria community using the ICE system.
The first system
Our “degrading power” is as already mentioned- the cellulase enzyme. We used Endo5a cellulase, that breaks 1,4 beta bonds. In the future, it would help us degrade wet wipes based on cellulose fibers. In addition, in the future we consider adding other cellulases to break other bonds, since only one cellulase is not enough for us.
Another important molecule in the first system is the CBD-cellulose binding domain. Its purpose is to bind the cellulose polymer thus, enriching the cellulose surface with cellulose degrading bacteria, so the degradation will be more efficient.
The last component in this system, is AIDA-I. It is a monomeric auto transporter. It has a very important role of displaying both the cellulase and the CBD on the bacteria’s surface.
The second system
The second system we used is based on “ICE” elements. ICEs are mobile genetic elements which contain genes that allow them to integrate into a host genome. They are passively distributed during cell differentiation. The usage of those mobile elements has a huge potential transforming DNA parts to different DNA receptor cells.
ICE elements contain 3 main sections:
- Pore genes- that encode for protein channels. (Through which the DNA may be imported)
- Genes that encode to proteins that recognize the ori-T, and cause the transfer of the single stranded DNA from the donor to the receptor cell.
- Genes that encode to the integrase\recombinase proteins, which are responsible for the integration of the DNA to the host’s chromosome.
Even though ICE system was mainly a theoretical plan for us, due to COVID-19 that prevented us from being physically in the lab for long periods of time, ICE has a huge potential assisting our project in the future. With the help of ICE elements, we would be able to insert the first system (containing Endo5A, CBD and AIDA-I) to the bacterial community in sewer systems, and enable major distribution of those genes and qualities among it, which will hopefully help preventing the creation of fatbergs.