Team:TJUSLS China/Implementation
General introduction
PET, polyethylene terephthalate, is a synthetic plastic material with abundant reserves, with an annual production of nearly 70 million tons worldwide. This material is widely used in packaging, construction, electrical appliances and so forth, such as beverage bottles, packing tapes, mobile phone films, and insulating materials in circuits.
PET can not be used for a long time but repeated thermal-mechanical recycling is also not good for PET. Its quality will be greatly reduced with recycling. The use of incineration and other methods will also produce a large number of chemical substances harmful to human. The use of traditional physical thermoplastics, chemical incineration and other treatment methods is no longer in line with the development trend of today's society.
The low price of PET makes industries favor to use it and its recycle-unable feature makes it waste a lot of resources. Its good stability makes it difficult to be degraded. So, it usually exists in nature in a stable shape. These PET that failed to be reused will cause continuous and hard-to-treat damage to the environment.
Therefore, we urgently need a way to deal with PET reasonably, so we enter the field of biodegradation, hoping to find an enzyme that can decompose PET. In previous attempts, we have found some enzymes that can decompose PET. These enzymes can decompose amorphous or low-crystallinity PET to a certain extent. But their stability is very poor, it is difficult to decompose high-crystallinity PET, which exists in the form of plastic bottles, etc.
Our team aimed to improve the thermal stability of the PETase and tried to use it to decompose some highly crystalline PET to improve the actual catalytic efficiency of the PETase. We conducted a series of experiments to try to improve the enzyme performance and heat resistance. We finally got a great result: the PETAres designed by us shows an efficiency 163 higher than wild type and the Tm of which have increased by (?) It will greatly promote the process of PET degradation and reuse. The problem of plastic pollution will be solved to a large extent. At the same time, related industrial enterprises such as PET production and recycling are also likely to make a new round of revolutionary progress.
Our recommended end users
- Companies that produce, recycle, and reuse PET products
- Garbage treatment plants
- Environmental protection organizations, etc.
Our team have investigated some local PET production, sales and use enterprises and retailers on the spot, including Tianjin Wanshihao Trading Co., Ltd., Tianjin Wanxinyu Insulation Material Co., Ltd., and 7-Eleven convenience stores. From these companies, we understood the process of PET plastic from production to sales to use. From the chemical synthesis of PET to the production of rod-shaped or plate-shaped materials, the PET material is preliminarily shaped and then transported to the next-level production company to make plastic bottles, plastic-steel straps and other types of products for sale and use.
As far as we know the price of PET raw materials is not cheap among all the plastics commonly used. However, the recycling rate of this material is relatively low among all plastics. When recycled and reused, the properties of PET, such as toughness and transparency, will be greatly compromised. Taking plastic steel straps as an example, the price of straps made of secondary material (re-used PET) is one-third of the price of the first material.Because there are visible impurities in the material, and it is more brittle than the first material. Therefore, compared to recycling directly, a better way is to use biological methods to decompose it into raw materials and synthesize PET from scratch.
We introduced our project to these companies and retailers. Tianjin Maosheng Renewable Resources Recycling company stated that it is because of the low quality of the RePET products that most manufacturers have obtained, they still use a large amount of PET synthesized from scratch. He advised us to investigate about the willingness of other factories to purchase PET made by our enzymolysis-synthesis with no performance loss at a lower price. He also said that our degradation method can greatly save their expenses and improve their recycling efficiency, hoping to introduce our degradation system. They said that this approach is very peculiar and believes that our project has great potential. If our products can be put into industrial applications normally, they are willing to come into contact with this method.
The way other people use this project in our vision
We uploaded and displayed our results on our website, and tried to contact some traditional recycling plants and processing plants to introduce our projects to them. After our PETase finished products are made, we may donate the products to others or sell the patent.
Implementation of our project in the real world
After rounds of experiments and selection in the laboratory, we have selected several kinds of highly effective PETase. Among them, super5 can degrade nearly 163 times of PET into MHET compared to wild type. We will use E. coli as our engineered bacteria to express our Super5 enzyme and the LCC enzyme modified by our partner BJEA. Then they are collected purified and transferred into the fermentation tank. To prepare the PET ready for degradation, the waste PET will firstly be collected and pulverized. It will be washed with detergent, Na2CO3 and water and then turned into the fermentation tank. In the fermenter, the two enzymes will respectively degrade the high and low crystallinity regions of the PET material, and finally get a mixed solution of MHET，EG，TPA and BHET, which will be used in the synthesis of the PET material to achieve a closed loop.
Safety
During our experiment, no harm to humans and the environment due to PETase has been found yet.
