Team:Kyoto/Human Practices/Gold
Gold
Overview
In the beginning of our research, we interviewed a Japanese textile company "T" and learned about synthetic fibers. They even provided us with samples to do experiments. Inspiration for next approach came from the experts of a wastewater treatment plant. We learned there are three methods to process wastewater; filtration, precipitation, and degradation. Comparing these three systems, we decided to precipitate fibers. However, since microfibers do not precipitate well on their own, we needed fibers to be aggregated. The third expert from Sanyo Chemical Industries taught us about flocculants that have many binding surfaces. With this in mind, we found the best protein for our device - Encapsulin. Through our Human Practices, we changed our ideas and perspectives, finally deciding on our device - thanks to the experts.
Distance to Our Solution
Learning About Fibers
Japanese Textile Company "T"
At first, we interviewed a Japanese textile company “T” to learn more about synthetic fibers. According to the staff, various types of polymer such as acrylic, nylon, polyester, and polypropylene are used in synthetic fibers. Among them, the most prevalent fiber was PET (Polyethylene terephthalate) fiber. Thus, we decided to target PET fibers, as they might be the major plastic particles in the wastewater.
They also provided us with the industrial standard sample of PET fibers. Unlike fibers in consumer products, these fibers are clean, uniform, and not contaminated by dusts. Using these materials, we performed highly quantitative and reproducible experiments. You can see more detail on our result page (see Result).
Narrowing down Ideas
Wastewater Treatment Plant
Next, we visited a local wastewater treatment plant to know how they remove wastes from wastewater. According to the staff, there are mainly three methods; precipitation, degradation, and filtration. In the plants, wastewater is first stored stably so that bigger wastes could be settled down. Flocculants are used to aggregate and precipitate smaller particles such as starch grains and pigments. Then to remove wastes that are not precipitated, plants apply the next method, degradation. In the activated sludge tank, small wastes are degraded by bacteria. Some plants apply another solution, using a fine mesh filter, to remove wastes. However, this method is not widely used.
We decided to focus on one of the three methods to remove microfibers. Among the three methods, filtration was not an appropriate way because it costs and needs frequent maintenance. This is why most of the plants do not apply the filtration system. Thus, we considered which system we improve; degradation or precipitation. We could not choose easily because these two methods also had challenges.
The staff also gave advice about our device on where to apply our device. They said that plants would not tackle a microplastic problem on a large scale, as there is no legal measurements for the problem. It is more effective that individuals make efforts at home to reduce microplastics. Therefore, we decided to make device applied directly to the drainage pipe of the washing machine (see Hardware).This human practice had a good impact also on the modeling part because they taught us the velocity of wastewater and how long it takes to process it (see Modeling).
Deciding Approach
Past iGEM Teams
Looking at previous iGEM teams, many teams dealt with microplastic problem to degrade plastics. However, it seemed difficult to degrade plastics efficiently. So, we gave up developing degradation system. On the other hand, some teams demonstrate the efficiency of plastic-binding proteins. We thought that displaying plastic-binding protein on the surface of E.coli and injecting it into washing wastewater, can make fibers to aggregate and precipitate them
(see iGEM History).
Discussion with Public
At the Kyoto University Academic day 2019, visitors were also concerned about microplastic problems. They said if we made an ideal device, they would like to buy it. However, they would never accept GMOs as they still had a negative impression on them. This made us concern how to aggregate fibers without using GMOs products
(see Academic day).
Through these researches, we decided to aggregate and precipitate fibers with non-GMOs products.
Overcoming The Challenge
Sanyo Chemical Industries
In order to discuss what we use and what features the device should have to precipitate microfibers, we visited Sanyo Chemical Industries, which produces flocculants. According to the staff, flocculants are polymers and therefore have numerous binding sites, and few flocculants can bind to substances that don’t have an electric charge. So most of the flocculants cannot bind to microfibers. Instead of using GMOs, polymer protein which has flocculant-like properties could be useful to aggregate fibers. If we find the protein, we could overcome the problem of biological safety.
Conclusive Solution
To realize our plan, we found an ideal protein which has a property like that of flocculants, Encapsulin. Encapsulin is a protein-made capsule-like nanostructure and we can attach any protein on both of its outside and inside surface. It is expected to aggregate microfibers efficiently because it has more plastic-binding proteins to its surface than other dimer proteins. In addition to the property, it is not a GMO, but just a protein, which makes it biologically safe to use at home. To sum up, Encapsulin, which has plastic-binding protein is the most suitable tool to settle microfibers as precipitation.
