Integrated Human Practice

Overview

In this year’s integrated human practices, the HBUT-China team primarily focused on documenting the project’s development process, explaining the background and principles at each stage, and illustrating the feedback loop between our project and the world. Through engaging with global stakeholders, we ensured that our project contributes to solving the issue of plastic pollution while promoting sustainable development.

In our integrated human practices, we explained why we chose plastic pollution as our project theme and demonstrated the background research we conducted to ensure our work is grounded in reality. We took into account the opinions of stakeholders and consulted experts during the project design process. Finally, we summarized our efforts to inspire other iGEMers working on related projects to join us in these endeavors.

Part 1: Theme Selection

Theme Selection---Raising Awareness of Plastic Pollution in Daily Life

Plastic has become an indispensable material in our daily lives, such as in water bottles, garbage bags, and food packaging. However, plastic recycling efforts are often insufficient, and plastic waste is frequently seen on roads, in water bodies, and even in the air. Hubei University of Technology is located near the Xunsi River, where we regularly observe plastic waste in the water. This common sight led us to worry about whether this plastic waste might be polluting our environment and harming our health.

Figure 1. Photo of plastic waste in Xunsi River

In our daily lives, we sadly come across scenes like this. A sturdy tree stands tall under the sunlight, while at its foot, a small plant that has just broken through the ground is tightly trapped by a transparent plastic bag, struggling to grow. The plastic bag, though light and transparent, reflects the sunlight, yet it firmly suppresses this fragile life. We can’t help but think: the tree represents the stability of nature and the strength of life, while the trapped plant symbolizes the fragile life struggling in the midst of pollution and destruction. The plastic bag stands for the products of human society and the harm inflicted on the environment—it seems harmless, but imposes an invisible constraint on the ecosystem. Through this image, we feel the severe threat that plastic pollution poses to nature, and we reflect on our own responsibility. Every piece of discarded plastic waste could become a shackle that hinders life. What can we do to reduce plastic usage, properly manage waste, and protect this fragile environment for our shared future, and for every tenacious life growing on this earth?

Figure 2. Plant trapped by plastic

Motivated by these concerns, we conducted extensive literature research on the topic.

In our daily lives, plastic has become indispensable due to its lightweight, durability, and cost-effectiveness. From plastic bags used in food packaging to essential items like smartphones, plastic and its derivatives are omnipresent. Jyoti Mathur Filipp, Executive Secretary of the Secretariat for the Intergovernmental Negotiating Committee (INC), pointed out that approximately 430 million tons of plastic are produced globally each year1, with two-thirds having a short lifespan and quickly becoming waste. Moreover, according to data released by the United Nations Environment Programme (UNEP)2 and the Organisation for Economic Co-operation and Development (OECD), the total annual production of plastic continues to grow exponentially.

Despite increasing global attention on limiting the use of plastic products and recycling, a large amount of plastic is still directly released into the environment. The massive generation and improper disposal of plastic waste (white pollution) have made it one of the most serious environmental problems. Additionally, discarded plastic products do not biodegrade, leading to the long-term accumulation of plastic waste, which pollutes soil and water sources3. It also poses risks of suffocation, poisoning, and death to marine life that ingests it4. These exposed plastic products undergo physical reactions, photodegradation, and other processes, forming microplastics that ultimately enter ecosystems and food chains, posing potential impacts on the entire ecosystem.

Over the past decade, numerous studies have shown that microplastics can be absorbed by crops, fish, earthworms, chickens, bees, and other marine and terrestrial animals, as well as humans, affecting their growth, development, and reproductive capabilities5. Microplastics can enter the human body through various pathways, including the respiratory system, digestive system, and cardiovascular system6. If they enter the body through the respiratory tract and accumulate in the lungs and airways, they may impact lung function and lead to respiratory health issues, with long-term risks of cancer. If they enter the body through the digestive system via the food chain7, accumulating in the intestines, they may harm the liver and intestines, disrupt normal hormone levels, and affect reproductive and developmental functions. Pathogenic bacteria and antibiotic-resistant bacteria attached to microplastics exacerbate their harmfulness, potentially leading to disease transmission and the spread of antibiotic resistance.

Part 2: Background Investigation

Section 1---Field Investigation

We collected water samples from rivers in Guangdong, Hubei, Shandong, and Jiangsu, China, and used the Nile Red staining method to detect the presence of microplastics in the water. The test results indicated that microplastics were commonly found in the river waters across these regions (the red particles represent microplastics).

Figure 3.
A. Jiangsu water sample test result
B. Hubei water sample test result
C. Shandong water sample test result
D. Guangdong water sample test result

In addition to this, we also tested the presence of microplastics in bottled drinking water in China. The results showed that microplastic particles were present in popular bottled drinking water brands in China, indicating that microplastics may have already entered the human body through water resources.

Figure 4. Bottled drinking water test result

Section 2---Public Survey

  1. To understand public perception of plastic pollution, we created a questionnaire and invited 661 members of the public to participate. The data shows that 79.88% of respondents are concerned about plastic pollution, and 21.48% take it very seriously, indicating a positive public attitude toward addressing plastic pollution.
Figure 5. Survey results on awareness of plastic degradation

We also surveyed the public’s knowledge of common plastic treatment methods, and the results show that most people are familiar with physical methods.

Figure 6. Survey results on understanding of common plastic treatment methods
  1. Additionally, we interviewed professionals involved in plastic waste management.

In an interview with an environmental impact assessor, we learned about the Chinese government’s stance on companies researching plastic degradation. In recent years, Shandong Province has implemented a series of restrictions on plastic products. Under new regulations, Shandong has banned and restricted certain types of plastic products, including non-degradable disposable plastic bags, plastic cutlery, plastic cotton swabs, and cosmetic products containing plastic microbeads. Violations of these rules, including the production, sale, and use of these products, will result in fines. Furthermore, Shandong is encouraging the use of fully degradable agricultural films and alternative materials, such as bamboo products and degradable plastics, to reduce plastic pollution. These measures have initially shown significant results in reducing plastic waste and improving the environment.

In an interview with a recycling station owner, we found that the amount of plastic waste has increased significantly in recent years, with nearly double the amount of plastic waste being recycled compared to previous years. The owner mentioned that if there were technologies that could process plastic and generate economic value, it would encourage more people to participate in recycling efforts, thereby alleviating plastic pollution.

In an interview with a sanitation worker, we learned that plastic bags, water bottles, and beverage bottles, such as milk tea containers, are the most frequently collected items in daily work, with plastic accounting for up to 80%. Collecting plastic waste along riversides is especially challenging. In their work area, residual agricultural films have become entangled in the mud, making them very difficult to clean. The worker expressed hope for future technologies that could naturally degrade plastic, reducing the pressure on waste collection and recycling.

Figure 7. Interview with a Sanitation Worker

Section 3---Exploring Solutions to Plastic Pollution

To explore solutions for plastic pollution in depth, we consulted Professor Leng Yifei from the School of Environment at Hubei University of Technology. Professor Leng’s research focuses on emerging environmental pollutants, ecological health assessments, ecotoxicological effects, and bioremediation technologies in soil and water environments, making significant contributions to environmental protection.

Professor Leng first introduced us to the global plastic market, highlighting that PET plays a key role. PET accounts for around 20% of all plastics, with the global packaging industry being the largest end-user. The production of plastic packaging is expected to increase from 140 million tons in 2023 to approximately 180 million tons by 2029, leading to an urgent need for PET recycling solutions. Professor Leng identified three main approaches to PET recycling: physical, chemical, and biological methods.

The primary physical degradation methods for PET include photodegradation and thermal decomposition. However, photodegradation is highly dependent on environmental conditions; without light or when plastic is buried in soil, degradation cannot occur, limiting the effectiveness of degradable plastics. Chemical degradation methods for PET, such as hydrolysis, glycolysis, and methanolysis, also have limitations due to high energy consumption and the need for extreme temperature and pressure conditions, which increase both energy use and production costs.

Compared to physical and chemical methods, biological degradation is more energy-efficient, time-saving, and environmentally friendly, aligning better with societal development trends. Biological methods include microbial degradation and enzymatic digestion. Despite their advantages, these methods still face several challenges:

  1. Strict Degradation Conditions: Degradation must occur under high temperatures and alkaline conditions. PET’s glass transition temperature is 70-80°C, and only in this amorphous state can PET bind with enzymes for degradation. Additionally, the degradation process requires an alkaline environment (pH 7-11), making the conditions more stringent for enzymatic reactions.

  2. Low Degradation Efficiency: The natural expression of PET-degrading enzymes is generally low, limiting their efficiency and cost-effectiveness in industrial applications.

  3. Inhibition from Intermediate Products: During PET degradation, enzymes release intermediates such as MHET, BHET, TPA, and EG. Accumulation of these intermediates, particularly BHET and MHET, can inhibit enzyme activity and hinder further degradation of PET.

  4. Limited Methods for Recycling Degradation Products: The current recycling methods for PET degradation products are limited, leading to low utilization rates. While some small molecules like protocatechuic acid (PCA) and vanillin can be produced through transgenic and whole-cell catalysis, other products like TPA and EG are often metabolized or mineralized directly, rather than being used to produce high-value compounds. This results in carbon loss, which does not align with the goals of a circular economy for PET.

This consultation provided us with valuable insights, and we plan to address these issues in our project development.

Figure 8. Interview with Professor Leng Yifei

Part 3: Initial Project Design

After gathering sufficient background information, we began the preliminary design of our project, aimed at addressing both plastic degradation efficiency and the recovery of degradation products.

In choosing a chassis cell, we aimed to solve the issue of low degradation efficiency in biological methods. We first considered Pichia pastoris, as literature research showed it to have strong capabilities for expressing foreign proteins. Pichia pastoris has a strong AOX1 promoter, allowing it to produce foreign proteins in quantities that account for 20%–30% of total protein production8. Additionally, Pichia pastoris secretes extracellular enzymes, enabling the application of crude enzyme extracts directly for plastic degradation, thus bypassing the need for cell lysis and protein purification, saving time and costs9. On the other hand, commonly used E. coli expression systems tend to have issues with inclusion bodies and endotoxins. Hence, we selected Pichia pastoris as the chassis cell for our project. After discussing the project design and application background with two executives from Angel Yeast, they approved of our decision to use Pichia pastoris as the chassis cell.

Figure 9. Interview with Angel Yeast Executives

In our work on PET hydrolases, we identified two highly efficient PET-degrading enzymes, IsPETasePA and FAST-PETase-212/277, from literature, both capable of degrading more than 99% of PET10 11 12. However, these enzymes require temperatures of 40–50°C and more alkaline conditions to achieve maximum activity. To address the challenge of modifying enzymes to operate under less stringent conditions, we consulted with Dr. Cheng Li, a research scientist from MIT with significant achievements in synthetic biology. After learning about our project design, Dr. Li endorsed our approach and suggested combining machine learning to improve enzyme activity or thermostability with glycoengineering to enhance enzyme tolerance to acidic and alkaline conditions, thus improving its industrial application and contributing to environmental solutions.

Figure 10. Research scientist Dr. Cheng Li explaining enzyme modification techniques

To mitigate the inhibitory effects and recovery issues of degradation products EG and TPA, we plan, based on literature research, to co-culture _Pichia pastori_s with Komagataeibacter xylinus to convert TPA and EG into bacterial cellulose (BC). It is known that EG and TPA promote the production of bacterial cellulose13. BC, apart from its widespread use in the food industry, possesses high purity (lacking lignin, hemicellulose, pectin, and other biological components), high crystallinity, excellent mechanical strength, water retention capacity, biocompatibility, and biodegradability14. These characteristics make BC highly suitable for emerging fields, such as biomedicine15, cosmetics16, packaging materials17, water treatment18, and functional textiles19.

Part 4 Project Design Improvement

After confirming the significance and feasibility of our project, we visited Lecturer Li Kai from Shanghai Jiao Tong University, who has extensive knowledge of bacterial cellulose. During our visit, we introduced our experimental plan and progress, discussing with him how to balance the growth of the two microorganisms in co-culture. He suggested switching from co-culture to mixed culture, allowing both microorganisms to better exert their effects. We adopted this suggestion and verified its feasibility in wet lab experiments, which produced favorable results(https://2024.igem.wiki/hbut-china/results/). As a result, we replaced co-culture with mixed culture, further refining our project. For more details, please refer to (https://2024.igem.wiki/hbut-china/experiment/).

Figure 11. Interview with Lecturer Li Kai

Part 5 Positive Feedback

(1) To ensure the development potential of our project, the technical director of Angel Yeast, after watching our experimental report, emphasized that plastic degradation is a crucial direction for both food safety and human health in the future. This is a very important research area that requires collective effort and exploration to address.

(2) To ensure that our project has economic viability, we contacted Professor Zhang from the School of Economics and Management at Hubei University of Technology. She mentioned that bacterial cellulose (BC), as an environmentally friendly biomaterial derived from the transformation of microplastic PET, shows broad application prospects in various fields due to its high purity, high water absorption, excellent mechanical strength, and biocompatibility. With the increasing global emphasis on sustainable development, market demand for BC continues to grow, supported by technological advances and policy support. Additionally, the rise in consumer environmental awareness enhances the market appeal of BC, making it a product with significant market advantages and immense potential in the field of sustainable development.

(3) After completing our experiments, we reconnected with Professor Li Kai from Shanghai Jiao Tong University. We provided him with an improved version of our experimental introduction and detailed the design and results of our mixed culture. He then expressed his strong confidence in our project and eagerly anticipated its performance in potential industrial applications.

Figure 12. Email from HBUT-China to Professor Li Kai

Figure 13. Professor Li Kai’s reply email

(4) After completing our experiments, we also reached out to Dr. Li Cheng, a research scientist. We discussed the experimental results regarding enzyme modification with him, and he stated that these results provide important insights for optimizing enzyme performance and improving degradation efficiency. This lays a solid foundation for further exploration in the field of plastic degradation. He looks forward to future research based on these findings, exploring the enzyme’s adaptability under different environmental conditions and its potential for industrial applications, thereby promoting the continuous advancement of plastic waste treatment technologies.

Part 6 Integration of Human Practices

This year, our HBUT-China team is focusing on synthetic biology education for all age groups, with a particular emphasis on children aged 5-12. We have conducted a series of activities to promote synthetic biology and iGEM, aiming to increase awareness and encourage participation in our project, while gathering feedback along the way.(https://2024.igem.wiki/hbut-china/education/)

At the same time, our HBUT-China team is dedicated to developing more efficient, cost-effective, and eco-friendly plastic degradation technologies, with the goal of recycling plastic degradation monomers into bacterial cellulose, which can be used in everyday skincare products. We believe that the concept of our project aligns closely with the United Nations’ Sustainable Development Goals in the area of environmental protection, and we aim to use synthetic biology as a tool to demonstrate its value in plastic degradation, waste recycling, and environmental improvement..(https://2024.igem.wiki/hbut-china/sustainable/)

Additionally, our HBUT-China team has carefully considered how to select target groups and help them access the same educational opportunities. We aim to listen to their needs and understand the barriers they face in participating in synthetic biology. Our goal is to expand the reach of synthetic biology widely and explore how to build an inclusive scientific community.(https://2024.igem.wiki/hbut-china/inclusivity/)

References

Footnotes

  1. A historic treaty to curb plastic pollution is expected to be reached | | 1 United Nations News ↩ ↩

  2. Accumulation ofplastic waste during COVID-19. Science 369(6509), 1314-1315. ↩

  3. Coleby, A.M.and Grist, E.P.M. (2019). Prioritized area mapping for multiple stakeholdersthrough geospatial modelling: A focus on marine plastics pollution in HongKong. Ocean and Coastal Management 171, 131-141. ↩

  4. Alomar, C.,Sureda, A., Capó, X., Guijarro, B., Tejada, S. and Deudero, S. (2017).Microplastic ingestion by Mullus surmuletus Linnaeus, 1758 fish and itspotential for causing oxidative stress. Environmental Research 159, 135- 142.。 ↩

  5. Jing, Nannan, et al. “Research Progress on PET Plastic Degradation and Modification Methods of Its Degrading Enzymes.” Journal of Petrochemical Universities 37.1 (2024). ↩

  6. Prata, J. C. (2018). “Airborne microplastics: Consequences to human health?” Environmental Pollution, 234, 115-126. ↩

  7. Porter, A.,Lyons, B.P., Galloway, T.S. and Lewis, C. (2018). Role of marine snows inmicroplastics fate and bioavailability. Environmental Science and Technology52(12), 7111-7119. ↩

  8. https://baike.baidu.com/item/%E6%AF%95%E8%B5%A4%E9%85%B5%E6%AF%8D/9301649?fr=ge_ala#3 ↩

  9. Chen C C, Li X, Min J, et al. Complete decomposition of poly (ethylene terephthalate) by crude PET hydrolytic enzyme produced in Pichia pastoris[J]. Chemical Engineering Journal, 2024, 481: 148418. ↩

  10. GAO Y, ZHENG Y, QI Z, et al. Enhancing the biodegradation of bis(2‐hydroxyethyl) terephthalate by an IsPETasePA and MHETase dual‐enzyme system [J]. Journal of Chemical Technology & Biotechnology, 2024, 99(8): 1860-70.↩ ↩

  11. CHEN C-C, LI X, MIN J, et al. Complete decomposition of poly(ethylene terephthalate) by crude PET hydrolytic enzyme produced in Pichia pastoris [J]. Chemical Engineering Journal, 2024, 481: 148418.↩ ↩

  12. Shosuke Yoshida et al. A bacterium that degrades and assimilates poly(ethylene terephthalate). Science, 351, 1196-1199 (2016). ↩

  13. Esmail A, Rebocho A T, Marques A C, et al. Bioconversion of terephthalic acid and ethylene glycol into bacterial cellulose by Komagataeibacter xylinus DSM 2004 and DSM 46604[J]. Frontiers in Bioengineering and Biotechnology, 2022, 10: 853322. ↩

  14. Zhong C. Industrial-scale production and applications of bacterial cellulose[J]. Frontiers in Bioengineering and Biotechnology, 2020, 8: 605374. ↩

  15. de Mattos I B, Nischwitz S P, Tuca A C, et al. Delivery of antiseptic solutions by a bacterial cellulose wound dressing: Uptake, release and antibacterial efficacy of octenidine and povidone-iodine[J]. Burns, 2020, 46(4): 918-927. ↩

  16. Morais, Eduarda S ,Silva,et al.Anti-inflammatory and antioxidant nanostructured cellulose membranes loaded with phenolic-based ionic liquids for cutaneous application[J].Carbohydrate Polymers, 2019, 206:187-197. ↩

  17. Shi Z, Zhang Y, Phillips G O, et al. Utilization of bacterial cellulose in food[J]. Food hydrocolloids, 2014, 35: 539-545. ↩

  18. Mautner A , Bismarck A .Bacterial nanocellulose papers with high porosity for optimized permeance and rejection of nm-sized pollutants[J].Carbohydrate polymers, 2021, 251:117130.DOI:10.1016/j.carbpol.2020.117130. ↩

  19. da Silva C J G, de Medeiros A D L M, de Amorim J D P, et al. Bacterial cellulose biotextiles for the future of sustainable fashion: a review[J]. Environmental Chemistry Letters, 2021, 19: 2967-2980. ↩