Team:SMS Shenzhen/Human Practices

Before the project was launched, SMS surveyed to determine how many people were aware of gum pollution in the city. The survey results showed that while gum contamination is widespread, most people ignore this common contamination. SMS, therefore, wanted to develop a technique for rapidly degrading gum using synthetic biology and consulted experts to optimize the experimental method. In addition, SMS also conducted interviews with stakeholders in the gum issue. Based on interviews and mutual feedback with stakeholders, we summarized their fundamental needs, and combined with our project; we developed the hardware of the project -- gum cleaner. In the meantime, SMS hopes to raise public awareness of the gum issue and has organized an online and offline art exhibition to arouse general thinking about the subject.

Figure 1 | Mindmap of iHP in SMS_Shenzhen 2021

Defining the Problem

The Field Tests

During the brainstorming process, we came up with the idea of cleaning chewing gum by ourselves using the highest-ranking gum disposal methods. We attempted different methods, including using (a) acetic acid, (b) water, (c) shove and egg white, and (d) acetic acid and egg white.These methods are all the most popular and claimed to be effective ones on the internet.

Our fieldwork discovered that although the methods did work to a certain degree, some gum, especially the part sticking on the ground, was always left uncleaned. And, most importantly, all these methods require a lot of time and physical work. Therefore, a new approach with efficiency, effectiveness and does not require further work is needed.

The Survey

Before everything started, we wanted to figure out whether there was a need for our project during the brainstorming process. We distributed online questionnaires to explore the public's views on chewing gum pollution and their expectations of our product. We published them on multiple public forums and social media sites. To ensure the authenticity and validity of the questionnaires, we set up a question to check whether the answer is valid and protect it by protecting the participant's privacy.

Survey result -- Places and Frequency of Discovering Chewing Gums

"Where do you think chewing gum is usually found?" Only 11.6 percent thought the gum around them was properly disposed of, while more than 87 percent found gum in public that was not properly disposed of. This shows that chewing gum is an issue that has been noticed by the public and our project is needed by society. Fifty-seven percent said they noticed gum contamination only occasionally, while only 8.5 percent said they noticed it regularly in their lives. This result is actually different from Question 3. There is a good explanation for the difference. It's much easier to notice gum being thrown around now, so when we ask about gum contamination, people react differently than when they answer directly about gums being thrown around. Basically, people don't realize the seriousness of environmental pollution caused by gum throwing. So there's a need for a lot of publicity about the environmental risks of chewing gum.

Designing our Solution

Interviews with Experts

After we determined our project and our experiment's main technology roadmap, we've decided to interview several experts in the field of modeling and directed evolution to help make greater progress for our project.


In the early days of modelling, we came up with several ideas about possible models that can help improve our project: the pathogen propagation model that illustrates the harm of residual gums, the degradation model that illustrates the degradation process of our enzymes, the bacterial growth model that illustrates the growth of E. Coli, and the rational design that helps design proper mutants. However, since we weren't confident in our knowledge about the requirements and mathematics in biological modelling, we spoke to two experts in semiconductor simulation and gene circuit designing, who gave us insight into designing and improving our models.

We spoke to Xu Ying, the School of Materials Science and Engineering of Shenzhen University student, the head of modelling for the SZU_China team in the 2020 iGEM competition. Her research direction is semiconductor simulation.

Our team had just started a literature review on the four models that we conceived during our modelling. We did not know much about the mathematical equations and the specific significance of each of our models. For the degradation model, we had not found any proper mathematical models since we did not consider the degradation of the enzyme into parameters in the model. Miss Xu informed us about this problem during our literature review and proposed the Michaelis–Menten equation——it takes an equation describing the rate of enzymatic. For the bacteria growth model, we first considered the variants of population models. After exchanging ideas with Miss Xu, she recommended that rather than building a bacterial growth model, it is better to establish an enzyme expression prediction model, in which the direct experimental measurement of bacterial growth can be done with simple calculations, and the prediction of enzyme expression may be more necessary. For the pathogen propagation model, she inspired us to try the Brownian Motion to simulate pathogen movement. Last but not least, she helped us clarify the ideas of rational design by expounding each step in the sound design.

Using these suggestions, our team investigated these recommended mathematical equations and improved each model accordingly. With Xu's ideas, our team better combined each model into our project. For example, using the Michaelis–Menten equation, we designed a new concept to help demonstrate and visualize the enhancement in enzyme activity in the rational design.

Based on the suggestions provided by Miss Xu, we set up our models through calculation and illation. However, we found errors in plotting the ultimate graph while building the expression model using the Ordinary Differential Equations (ODEs). After debugging by ourselves, we conceived that the inserted parameters were inaccurate, but we haven't found any solutions to this problem. Therefore, we spoke to Mr Sun, a PhD candidate at the Institute of Microbiology, University of Chinese Academy of Sciences; his primary research direction is the principle of robust gene circuit design. He has many years of experience in leading the iGEM team as well.

After discussing our problems with Mr Sun, we realized that our error was mainly caused by solving the ODEs manually instead of using MATLAB. He also noted that we could ignore the impact of the extension process on transcription and translation. With the help of his ideas and his instructions on using MATLAB, we successfully used MATLAB to solve our ODEs and derived an accurate graph that simulates the protein expression in E. Coli.

Directed Evolution

When we were designing the directed evolution experiments, we were confused by numeral plans because none of us had experience in carrying out analogical experiments. To choose a reliable method that can handle the evolution of E.coli expressing Laccase CotA with better enzyme activity, we consulted Shiyuan Li and Ruijuan Xiang about a series of problems. Shiyuan Li used to conduct directed evolution experiments, and he is passionate about educating the public about synthetic biology. Ruijuan Xiang, the PI of an iGEM team in Beijing, is experienced in purifying proteins. With their help, we determined the method of conducting directed evolution experiments and an efficient measure to test the enzyme activity of many protein samples.

Based on the suggestions provided by Miss Xu, we set up our models through calculation and illation. However, we found errors in plotting the ultimate graph while building the expression model using the Ordinary Differential Equations (ODEs). After debugging by ourselves, we conceived that the inserted parameters were inaccurate, but we haven't found any solutions to this problem. Therefore, we spoke to Mr Sun, a PhD candidate at the Institute of Microbiology, University of Chinese Academy of Sciences; his primary research direction is the principle of robust gene circuit design. He has many years of experience in leading the iGEM team as well.

We designed our project with the help of those experts . Click to know more about project design.

Improving our Project

The main goal of our human practices is to build mutually beneficial links between the stakeholders and promote the improvement of our project. Considering the purpose of our project and our products, we found it necessary to listen to different opinions from different stakeholders. We identify the following stakeholders who might be helpful in our project:

Chewing gum manufacturer

Chewing gum seller

City Management Department Director

Manager of Public Place

Street Cleaner

Interviews with Stakeholders

In order to form an intimate relationship with our stakeholders, we conducted a series of investigations with each of them.

We interviewed a chewing gum manufacturer to find some possible and practical methods to produce self-degradable gum.

As soon as we determined the theme of our project, we devised many ideas about ways to alleviate the detrimental environmental effects caused by chewing gum. The highest approbatory scheme was designing self-degradable gums, wrapping papers that could help with gum degradation and an enzyme solution that could degrade gum. To figure out the feasibility of our ideas, we interviewed a specialist in gum production.

According to the data provided by the specialist, their plant produces about 3 billion tones of gum per year, which underscores the importance of mitigating the detrimental effects on the environment caused by gum. At the same time, we learned that it is challenging to design and produce a package that can help with gum degradation through the interviews. In addition to the effectiveness of the product and environmental impacts, we also need to consider security. Therefore, it is more challenging to mitigate the problem by devising a special environmental-friendly package or self-degradable gum. For that consideration, we decided to design a gum-degrade enzyme, which wouldn't contact the human body directly and is therefore much safer. Furthermore, the expert suggests that enveloping enzyme solutions into chewing gum indicates the insecurity of the scheme. So, we abandoned that conception. Also, the expert challenges the safety and effectiveness of reducing the environmental effects of chewing gum by modifying the wrapping paper, which enhances our decision on alleviating the problem in other ways.

Conclusion from manufacturer:

Their suggestions:

1. Producing a package that can help with gum degradation is challenging.

2. SMS needs to consider security when designing the product.

3. Experts challenge the safety and effectiveness of reducing the environmental effects of chewing gum by modifying the wrapping paper.

Our response:

1. We discarded the proposal of inventing a self- degradation enzyme gum due to safety and conductivity problems.

2. We proposed adding more novel details to our gum package to improve safety of our product.

To find the opinion of gum retailers' view of the necessity of gum cleaning solutions, expectations for gum cleansers, and the promotion of the proper disposal of gum by gum producers, we interviewed convenience store owners.

Convenience store owners said they value customers' ideas more than other factors when picking up brands and quantities of gum for supplies. At the same time, convenience store owners said chewing gum makers rarely promote correct disposal to retailers, indicating a certain lack of publicity. The retailer said he felt that the publicity was necessary, reflecting that he believed that spitting chewing gums to the ground is a universal phenomenon and that proper publicity could be an excellent way to reduce the phenomenon's occurrence. In terms of gum cleansers, the retailer thinks that if the cleaning is effective and portable, he is willing to use or even try to buy and sell it.

Conclusion from manufacturer:

Their suggestions:

1. SMS needs to value customers' requirements when considering making our product in commercial fields.

2. Chewing gum makers rarely promote the correct disposal of chewing gum to retailers, which further proved the necessity of our project and a certain lack of publicity for gum disposing.

3. The gum seller believed that if our product was effective and practical, there would be a number of customers.

Our response:

1. Though this interview convinced us of the necessity of our project, the proposal of selling the cleaning potion to sellers is still discarded due to safety reasons.

We found it also necessary to understand the government's views. Therefore, we interviewed the local City Appearance and Environmental Health Management Department. The City Appearance and Environmental Health Management Department of Luohu District City Management and Comprehensive Law Enforcement Bureau, Shenzhen, is the highest executive department of city appearance. They instruct the overall cleaning process of the sanitation workers to ensure that the clean streets offer citizens a sense of the city's cleanliness and promote their happiness. As for the government, they were not allowed to publicize their opinions, so unable to take any pictures or videos; we only had a brief conversation with them.

Starting with the issues of chewing gums, they admitted that they had encountered a substantial number of gums while working, which added difficulty to their cleaning work. These efforts indicated that the public's concept of "don't spit gums anywhere" was not enough, suggesting that we should increase publicity even for the children. Besides, according to them, although their common method - high-pressure water gun - can wash most of the gums, there was still some residue on the ground, forming black stains with dust. The lack of effective ways of eliminating the gums proves the importance and necessity of our project.

They were also kind enough to put forward constructive suggestions to our project, which directly affected our experimental goals and the necessity of our products. Through the conversation, they pointed out that most of the gums can be ideally removed by the current method, so our product needs to focus on removing remaining gums and dust, exposing the clean road rather than degrading the gum itself. If our product did not remove stains effectively, it was not as valuable as a water gun. Therefore, we should clarify the focus of the experiment (degradation of polyisoprene or effective removal of stains) to ensure the practicability of our products. Otherwise, our products cannot meet the needs of society or completely solve the problem of gum residue on the road.

We must consider other factors carefully too. For instance, they suggested that the degradation must be quick to increase productivity. Also, it is better to simulate different materials of bricks in the laboratory for biosecurity concerns.

Conclusion from manufacturer:

Their suggestions:

1. City management department director believed that a substantial number of gums had added difficulty to their work.

2. They suggested that we should increase the range and intensity for education and publicity, especially for children.

3. The high-pressure water gun failed to fully dispose of the gums, still some residue on the ground forming black stains with dust.

4. It is said that most of the gums can be ideally and largely removed by the current method, so our product needs to focus on removing remaining gums and dust.

5. They suggested that degradation must be quick to increase productivity.

6. They suggested us to simulate different materials of bricks in the laboratory for biosecurity concerns.

Our response:

1. We clarify the focus of the experiment (degradation of polyisoprene or effective removal of stains) to ensure the practicability of our products.

2. We proposed the plan of stimulating the effectiveness of our product on different materials in the lab.

3. We wrote instructions for our hardware, clarifying that it is harmless for humans and the environment.

4. We proposed to calculate the degradation time when testing our product in the lab.

To consider the issue from a manager's perspective, we interviewed the manager of a crowded park. We talked to a community director in Guangdong province Luo hu district to obtain some information and suggestions.

He said that in the community, cleaning chewing gum is one of the significant daily jobs for street cleaners, and it is a time-consuming and physically demanding job using the traditional method. After introducing our product to the director, he commented that it should be easy to learn and use, as most users would be the elderly. He also gave some valuable suggestions: we should consider weather and ground temperature when designing our product. When we asked him whether the amount of gum causing environmental pollution in the Wutong district varies with the seasons or some other factors, he claimed that during summer there is usually more gum than usual. During weekends, there is more gum produced than on weekdays.

Conclusion from manufacturer:

Their suggestions:

1. The product should be easy to learn and use.

2. The product should not require further cleaning, just spraying the cleaner.

3. They suggested we need to consider environmental factors in real life, e.g. weather, ground temperature.

4. The quantity of disposed chewing gum varies with the seasons, eg. More in summer than winter; more on vacation and weekends than weekdays.

Our response:

1. We conducted a long-term measurement of ground temperature in Shenzhen, in order to figure out the changing pattern of ground temperature.

2. We added suggestions on how to use the hardware instructions. Exp. We suggested that the product should not be used on rainy days.

As our final product will be used by cleaners, we must interview the street cleaners to understand the needs and suggestions. We also expected to gain some knowledge that actual cleaners can only obtain, for example, the present method of cleaning chewing gum.

We spoke to a couple of cleaners. On hot summer days, they need to squat on the ground to deal with traces of gum. These gum marks are often difficult to scrape off, so they have to squat for a long time to complete, resulting in sore knees and lower back. We learned about their experiences with gum stains and their expectations of gum cleaners. They agreed that chewing gum on the floor was difficult to remove because cleaners had to squat down to remove it, and there was a real lack of targeted solutions. If we plan to make cleaning tools that are small and convenient, we may solve big problems in their daily work.

Conclusion from manufacturer:

Their suggestions:

1. They hope we can design a product that can reduce their frequency of squating on the ground to deal with traces of gum which is very labor requiring.

Our response:

1. In order to invent a labor saving product, we had a brainstorm for our hardware.

2. We decided to add a scrapper with a long handle to our hardware, which is efficient in scapping off the gum and saving labor.

3. We've decided to let the city cleaners save more labor and reduce their frequency of bending down and squanting. So we've thought of pesticide sprayers as a good example.

Through our discussions with these stakeholders, we finalized their suggestions and needs.


challenge the wrapping paper, the current solution to reduce chewing gum poution.


had a limited awareness of the harm of gum pollution.

Management Department

pointed out that we should consider environmental factors, like ground temperature and weather.


have no effective tools to clean sticky gum marks.


Having identified the suggestions and needs from stakeholders, our team began brainstorming the hardware for users. We first discussed the form of our product. A modulated toolbox in which the inner parts are replaceable will be ideal for us. Our team also considers different usage scenarios, indoor and outdoor.

To discover more about the hardware, click the button below.

Investigating Ground Temperature

In our interview with the site manager of Wutong Mountain, the person in charge suggested that the amount of residual gum in tourist attractions varies with the seasons. In summer, as the flow of passengers increases, the number of residual gum increases. We can see that summer is the peak time to clean residual gum. Therefore, we made long-term observations of the summer surface temperature and weather conditions in our city——Shenzhen——to determine whether our enzymes' operating conditions fit the surface temperature in Shenzhen. We recorded the surface temperature for ten periods (one period represents ten days). The following chart is the result of our investigation.

Figure | Investigation of the surface temperature and weather in Shenzhen

According to the chart, the average surface temperature in Shenzhen's summer is about 42 Celsius, indicating the possibility of denaturalization for enzymes. Luckily, the denaturalization temperature for laccase CotA is high enough (about 90 Celsius) to keep its activity on the ground. Notably, the difference between forecasted temperatures and actual surface temperature is about 10 Celsius. Therefore, attention should be paid when predicting the surface temperature using the given temperature in the weather forecast. Besides, the average humidity is about 75% in Shenzhen, a coastal city south of the Northern Regression Line. The humidity condition is relatively friendly to the degradation process that occurs in the aqueous environment.

Consequently, through our investigation, the following conclusion is derived:

- The temperature condition on the ground is possible for our laccase cotA to operate normally.

- The humidity condition is favourable for degradation under an aqueous environment.

- When predicting surface temperature, operators should consider the difference between weather forecast temperature and surface temperature.

- This promoted our experiment, modeling and investigation of directed evolution.

Engaging the Public

From the interviews of City Management Department Director and Chewing Gum Seller, we recognized the importance of raising the public's awareness. Thus, we planned to organize an art exhibition, with eye-catching and impressive exhibits, to let the audience understand the severity of chewing gum issues, and therefore reflect on themselves to stop discarding chewing gum helps protect the environment.

BioArt Exhibition

Why this exhibition

After the research and interviews in the iHP section, we found that the public's understanding and attention to the harm of gum residues is very lacking. Therefore, we hope to draw people's attention to this issue in a novel and exciting way.

Our Aim

Draw people's awareness and provoke deep thinking in an artistic way.

Our Brainstorm Process

We discussed our ideas with Mr Shen from the Central Academy of Fine Arts. He suggested that we could make an art exhibition about our project. We then brainstormed the design of exhibits and how we would make them.

Now, let us introduce this novel exhibition to you.


The management of abandoned chewing gums in the urban environment is a blind spot. The gums that stick on the ground are called "city freckles" and "city peepers". According to our research, the traditional cleaning methods will consume many unnecessary human and material resources. In this regard, SMS_Shenzhen developed a cleaning liquid that can degrade gum base, hoping to contribute to the world's sustainable development.

However, all science and technology can do is degrade discarded gum. It is humans' awareness that could solve the problem. Therefore, we decided to use the exhibition to draw people's attention to gum problems and provoke deep thinking.

City peepers

These are sculptures of chewing gums. We preserved the abandoned chewing gums by making moulds and sculptures of the gum collected from the ground. We then glued the sculptures to the background board which looked like the ground. We hope that people will notice and realise that these easily overlooked black pieces are abandoned chewing gums.

Figure | The black pieces on the board were sculptures of gum.


This is a sandglass with chewing gums and our degrading cleaning liquid inside. The degradation of gum using enzymes is a slow and continuous process. We made this exhibit to show the gums gradually being degraded into liquid and reflect the sense of time.

Figure | BioArt---Time.


This is a team photo made from screen printing technology, using gums degraded to liquid form as ink.

Screen printing technology was originated in China more than 2000 years ago, and it is characterized by easy production and unlimited reproduction. Although raw materials have been improving over the past 2,000 years, the nature of this ancient printing process has not changed. We wanted to make people think about how the nearly 200-year-old gum can continue to play its original role, like screen printing, and improve itself, rather than becoming a forgotten voyeur in a fast-paced city.

Figure | BioArt---US.


These are two photos synthesised by photoshop. We took pictures of the gum in the corners of the city and used Photoshop to stitch them together on the gum residue and floor tiles. This kind of presentation brings a strong sense of visual impact and contrast to the viewers and makes the viewers aware of the prevalence of gum residue on the ground.

Figure | BioArt---Microcosm.

Looking into the Future

Gum pollution is still a serious and widespread problem among many different countries. Numerous organizations and companies are dedicating themselves to solving it. Through integrated human practice, our team realized the ponderance of gum pollution all over the globe. Moreover, we figured out that this pollution problem is still not paid enough attention to in the community. It is our duty to make more people realize the seriousness of gum pollution. In the future, we will keep popularizing our attitude towards gum pollution, especially in the young. Increasing publicity will be the main goal of our project in the future.