Ethylene terephthalate (PET) is one of the most widely used petroleum-based synthetic polymers, consisting of terephthalic acid (TPA) and ethylene glycol (EG) through ester bonds. Its low cost, portability, durability and gas blocking capabilities are widely used in beverage bottles, product packaging and textile industries. However, PET waste is highly durable and damp-proof, which inevitably causes serious environmental pollution. According to the United Nations, at least 8 million tons of plastic products leak into the ocean every year, resulting in economic losses of $8 billion, while seriously affecting the ecosystem and human health.
According to statistics, the global annual production of plastics increased from 200.0 million t in 1950 to 311 million t in 2014, and then increased to about 400 million t in 2022. It is estimated that the annual production of plastics can increase to 1.200 billion t in 2050. Plastic production increases year by year, and so does plastic waste. Forty-six percent of plastic is landfill, 22% waste, 17% burned, and 15% recycled. Among these, PET waste is the largest, most harmful and most persistent part of marine waste, accounting for at least 85% of all marine waste.
When broken down by weathering to produce microplastic particles smaller than 5 mm, these microplastics are often ingested by marine organisms and accumulate within them and are eventually transferred to the humans who consume them. Microplastics themselves have toxic chemicals, and they are easy to absorb pollutants and other toxic substances in the ecological environment. They accumulate into the human body through the food chain to produce toxicity, which may lead to cancer, birth defects, compromised immunity or other diseases. Therefore, it is urgent to find a method to treat PET plastic.
This year, we have studied a lot of previous research results and academic papers based on our accumulated experience over the years. We aim to achieve the efficient production of PET degrading enzymes by optimizing the enzyme expression system and chassis cell modification. We firmly believe that PETase will generate great potential value in the future of environmental protection, economic benefits and management innovation.
In order to explore the harm of plastic pollution and the potential ethical safety of biodegradation, we interviewed Zhang Jianchao, Tianjin University, "Beiyang Scholar-Young Backbone teacher".
From the perspective of geography and environmental science, Mr.Zhang deeply analyzed the complex impact of microplastics on the ecosystem. He noted that the existence of plastic organisms (tiny areas around microplastics), microbial populations that are different from other places, affects ecological processes such as methanogenesis and the natural circulation of elements such as carbon, nitrogen, phosphorus and sulfur. In addition, microplastics can also promote the abundance of pathogens and inhibit the growth of beneficial microorganisms, which may cause secondary harm to human health.
Regarding the cross study of biology and geology, Zhang Jianchao mentioned that his geological microbial team is trying to explore the influence of soil and other environmental factors on the functional expression of microbes, such as promoting the expression of key genes by regulating the mineral composition of soil and key nutrients variables. This approach focuses more on minerals and is different from the "Western medicine" directed direct intervention of synthetic biology. This provides new ideas for our team in terms of bioremediation technology.
We also asked Mr.Zhang Jianchao’s views on the comparison of bioremediation methods and traditional remediation methods. Mr.Zhang believes that the advantage of bioremediation is that it may have higher efficiency, and that it can effectively remove those pollutants that are difficult to be degraded by physical and chemical means through the action of biological enzymes. However, bioremediation also faces many challenges, and the strains with excellent performance in the laboratory may fail in the actual environment due to inadaptation, which is a major bottleneck for the wide application of this technology.
In addition, in terms of biosafety, Zhang Jianchao mentioned the possibility of damage to the local natural flora after the bacteria in the laboratory is put into the environment. Similar to ecological invasion phenomena, some powerful foreign microbes may threaten the survival of native species. The introduction of foreign genes may also trigger genetic contamination, and genes, such as resistance, may have unpredictable consequences when transferred from engineered bacteria to other species. This gives us a wake-up call that we should carefully assess and take steps to reduce these potential risks.
Also, we had the honor to have an online consultation with government personnel from Tianjin Science and Technology Bureau and Tianjin Ecological Environment Bureau, and further understand the current national policies on plastic pollution control. This has an important guiding significance for the future development of our projects.
We also interviewed Zheng Jie, president of Xiamen Stomatological Hospital, online to understand the use of plastic products in the hospital. President Zheng told us that most of the medical consumables used in the hospital are plastic products, but there is no distinction of categories (whether it is pet or not). After use, they are sent to the department specializing in treating medical waste as medical waste. In addition, according to the daily report provided by the hospital, a hospital area produces about 9.6138 tons of plastic medical supplies per year. It also shows that we cant live in plastic.
After collecting sufficient background information, we initiated the project design aiming to achieve efficient production of PET degrading enzymes by optimizing the enzyme expression system and chassis cell modification.
Our experimental design idea: By integrating relevant literature resources and combining with machine learning technology as auxiliary design tools, the optimized promoter and signal peptide sequences are designed to build efficient expression strains and improve the expression efficiency. Detailed design details can be found in the design section.
In the course of the project, our team was carefully guided by many teachers. Dong Mengjun from Tianjin University of Science and Technology discussed with us the construction of high-throughput screening system, which gave us a lot of valuable suggestions.
Zhu Chunfeng, a senior experimenter, provided important support in the use of instruments, especially in the training and daily operation of the centrifuge.
Engineer Li Yong gave us the instrument training related to microbial synthetic biology, and guided us to ensure the safety of the laboratory.
Dr. Xie Ziwen from the University of Liverpool, as an iGEM consultant, made important suggestions for our project design.
In order to improve the experimental ideas and better combine the mechanical learning technology, we interviewed Zhu Cheng —— Associate Professor, hoping that he could provide valuable guidance for our project.
He pointed out that the risk of signal peptide modification mainly depends on our understanding of the type of signal peptide and the combination of mutations, and the experimental results will depend largely on the adequacy of the sample size.
In terms of promoter optimization, Teacher Zhu suggested using the synthetic biology method to expand the scale of the promoter library and combine the adaptation of the promoter sequences and transcription factors of different strains.
In addition, he suggested building reporter systems, using tools such as green fluorescent proteins to assess the effects of promoters, and further optimizing the ribosome binding site (RBS) during translation. In view of our challenges in the transformation of gram-negative bacteria, zhu teacher pointed out, although most of the data we use from gram-positive bacteria, but the protein synthesis process of positive bacteria and negative bacteria and no essential difference, the key difference lies in the composition of the cell wall and cell membrane, so microbiology can explore the impact of these differences on the prediction model.
We had the opportunity to interview the environmental biotechnology direction PhD, food science professional lecturer, nutrition and health food (senior engineer) Xu Shujun teacher, is the current social attention of the food industry of micro plastic environment hazards, the present situation of plastic products and the future trend, and the application prospect of synthetic biology has carried on the thorough communication.
Microplastics refer to plastic particles less than 5 mm in diameter, which are widely found in the environment and have a profound impact especially on Marine ecosystems. These microplastics not only affect the food chain of Marine life, but may also be enriched through the food chain, causing potential harm to human health. Teacher Xu pointed out that although the direct toxicity of microplastics to the human body is small, but its long-term accumulation effect can not be ignored, especially in the long-term retention of adipose tissue, may have a long-term impact on human health.
Currently, the increasing coverage of microplastics problems in the field of food safety has also caused public concern in this area. Xu said that although there is still controversy about the health hazards of microplastics in food, existing technologies have been able to effectively control the pollution of micron-level plastic particles. However, nanoscale microparticles may pose greater risks due to their extremely small size. But other problems in the field of food safety, such as heavy metal pollution and pesticide residues, may pose a greater threat to human health.
Talking about the current situation and future trend of plastic products, Xu said that with the enhancement of environmental awareness and technological progress, biodegradable biological materials are gradually replacing traditional plastics. He predicted that in the next 30 years, the use of plastic will gradually reduce, but the advent of the Internet era, especially the rapid development of the takeout industry, has greatly increased the demand for plastic packaging, bringing great pressure to the environment. Xu called on all sectors of society to make joint efforts to promote environmentally friendly packaging and biodegradable materials to reduce the harm of plastic pollution to the environment.
When talking about the application prospect of synthetic biology in the field of food, Mr.Xu gave us an example. For example, synthetic biology can efficiently produce valuable substances such as antioxidant lycopene through advanced technologies such as gene editing and microbial fermentation, which is widely used in the fields such as food and cosmetics. The technology is easily industrialized and environmentally friendly, but it also faces ethical and safety challenges. Xu stressed that researchers should take full account of the possible ecosystem and genetic security risks while promoting technological development.
Finally, Mr.Xu put forward valuable suggestions to the students and teams who are interested in relevant research. He encouraged students to continue to explore interdisciplinary research and dig deep into the potential of synthetic biology in multiple fields. He also reminded students to focus on the research process and skills while pursuing project results. Xu believes that in-depth research will lay a solid foundation for future scientific research, and the process is more important than the results.
Through this interview, we learned about the wide application of synthetic biology in the field of food, and at the same time, Mr.Xu’s words also inspired us to move forward towards our goal!
We also interviewed the leaders of the TouchBase brand, a team dedicated to using cutting-edge environmental technology to skillfully turn recyclable plastic into creative cultural art.
He mentioned that the PET used for recycling textiles mainly comes from mineral water bottles, and the recycling of PET fibers is very small. Companies usually buy the plastic directly for recycling. An approximate 20% loss rate in the PET recycling process, although producing some by-products, can be overcome by biological methods.
However, for rPET (recycled PET) products, the market price and treatment cost are at a high level, compared with the traditional plastic treatment method, has not shown a significant cost advantage. As for the materials made of recycled plastic, there is no obvious difference with other fiber materials in terms of actual application or wearing experience, thus realizing the harmonious coexistence of function and environmental protection.
This is undoubtedly an innovative attempt in the field of plastic recycling, which has positive significance for promoting the practice and popularization of sustainable development.
We successfully designed the optimized promoter and signal peptide sequences and constructed efficient expression strains by x x%. The culture conditions were further optimized to establish an efficient ICCG expression system. The establishment of this system makes the production of ICCG significantly improve by xx times compared with the reported conditions (relative to 16 degrees), fully highlighting the excellent advantages of machine learning in the field of genetic modification.
The special feature of our project is combining literature research with machine learning techniques and using convolutional neural networks for prediction models. In communicating with Zhu Cheng, he mentioned the broad application prospects of mechanical learning and artificial intelligence in biology. In terms of development, such models will be able to comprehensively predict the structure of proteins, nucleic acids and small molecules. In the future, it is even new genomes to be designed through AI to create new species.