Team:SMS Shenzhen/Description
I bet you can find CHEWING GUM around you now, whether kept in a bottle, wrapped in paper or stuck on the ground.
Global Issue
Chewing gum is not a modern snack. Ancient people loved chewing gum just as much as we do. People started to enjoy the chewiness of gum since the Neolithic Age, which was proven by the excavation of a piece of 6000-year-old chewed birch pitch in Finland, 2007.[1] Not coincidentally, another part of 5700-year-old ancient birch pitch was found in Denmark, 2019, which was chewed by, after scientists' analysis, a young girl who "had dark skin, dark brown hair, and blue eyes".[2]
Figure 1 | The 5700-year-old "Chewing Gum"[2]
The advanced DNA sequencing technology even found the girl "was lactase non-persistent". Despite the girl's privacy not being protected well, such finding strongly shows that we human DO LOVE chewing gum, and chewing gum is indeed charming.
In modern times, chewing gum has experienced commercialization. John Bacon Curtis, credited as the inventor of chewing gum, turned spruce resin into a chewing gum product and changed it to a flavoured paraffin wax gum a few years later.[3] After that, a range of different chewing gum and chewing gum companies appear. Spherical and cubic shapes are developed for more fun; Lots of flavours are added from classic mint to new blueberry; Some extra components are also added, such as beads containing juice, for a richer texture. It is reported that people all over the world spend 14 billion pounds per year on chewing gum. And a gum manufacturing company said in our interview that they generate approximately 3 billion pieces of chewing gum annually.
Chewing gum has become a part of our lives. We chew gum on exam days to release stress. We chew gum on the metro to work to kill the boring commuting time. We chew gum before dating to create a memorable, mint fragrant night.
However.
Figure 2 | A man cleaning the "chewing gum wall" in Seattle, U.S.[4]
The massive chewing gum has caused severe problems.
Directly and most significantly, chewing gum makes cities around the world dirty.
London, New York, Shenzhen... Almost every metropolis suffers from improperly disposed chewing gum. A statistic in 2005 illustrates that there were 30 thousand pieces of chewing gum on Oxford Street, Britain.[5] And The Wall Street Journal once described chewing gum as the "Black Plague". Around us, the concern does exist as well. By interviewing the public place manager in Shenzhen, we learned that cleaning and disposing of chewing gum have always been critical for the workers.
Moreover, cleaning the chewing gum costs a large amount of money.
The statistic also shows that it costs 10 pens to clean a piece of chewing gum on the Oxford Street, and the UK government spends 50 million pounds every year on cleaning the gum.[5] The situation is similar in China. It takes 1.1 yuan on average to clean a piece of chewing gum on Tian'an Men Square.[6]
The chewing gum also brings loads of work to street cleaners.
Chewing gum is not easy to clean. In most situations, the street cleaners have only a shovel and a bottle of water, so it takes a lot of physical work and time to clean up a piece of chewing gum. Especially in hot summer, such work could be exhausting. Members in SMS_Shenzhen tried cleaning chewing gum and found it annoying to clean even a piece of chewing gum. Cleaning a street of chewing gum, thus, could be incredibly tiring.
There are also other health and environmental effects of chewing gum.
Research shows that chewing gum may be the ideal hotbed for pathogens to grow and reproduce. The current cleaning methods, which include chemical reagents, would bring adverse effects to the environment.
Overall, cleaning chewing gum is a severe global issue.
Define the problem
To solve the problem effectively, we first need to understand why is chewing gum so "sticky".
The component that contributes to the stickiness of the chewing gum is called the "gum base". It is a mixture of several polymers as shown in Table 1. Such chemical components make the chewing gum adhesive, stretchy, hydrophobic, and undegradable.
Table 1 The representative ingredients of gum base[8]
Although centralized incineration can produce toxic gases, it is the best treatment method at present. In addition to centralized burning, today's cleaning methods are primarily physical. The spray is applied to soften the gum base, and cleaners use shovels to remove the gum. However, as a city management director suggested in our interview, the gum base can not be completely cleaned up.
In brief, developing an environmentally friendly and efficient method to remove chewing gum is necessary.
Our Solutions
Cleaning
So we raised a question: are there any biochemical methods to degrade the gum base?
We quickly came up with the idea of enzymes. Enzymes are environmental friendly and efficient biocatalysts. After doing some research, we determine to utilize latex clearing protein (LCP) and laccase CotA to catalyze the degradation of gum base components, polyisoprene and ethyl vinyl acetate(EVA).
As the city management director said, a highly efficient method is needed. Thus we want to optimize the substrate affinity of laccase CotA by rational design, which is one of our modeling projects. The public area manager also reminded us that we should consider the ground temperature, so we want to adjust one characteristic of laccase CotA-the optimum working temperature-by directed evolution. The enzymes, LCP and enhanced laccase CotA, will ultimately be purified and made into a pre-mixed cleanser, which can clean the chewing gum by spraying it onto the gum.
However, a cleaner is not enough. Our project should offer service to those who clean the gum. We learned from the interview with a cleaner that current cleaning tools are not effective enough: the cleaner has to stoop or squat on the ground to clean the gum every time, which is extremely tiring for an aged person. Therefore, we designed hardware for cleaners to finish their job efficiently.
Prevention
Our product might help with cleaning out chewing gum. However, the amount of gum increases every day, so it is equally essential to prevent the gum from sticking on the ground. From preventing aspect, we came up with two objects that we could change: chewing gum itself and people's awareness of protecting the environment.
Thus, we planned to design a method to immobilize our enzymes, in which we embed the enzyme into the gum so that the gum would acquire self-degrading ability.
Moreover, we organized an all-aged science communication to interact with people in different age groups, teaching them basic concepts and knowledge of synthetic biology, raising their awareness of the chewing gum issue, and acquiring different opinions and perspectives from comprehensive audiences. We also carried out an art exhibition, using the language of art to evoke the audience's thoughts and show people the severity of the chewing gum problem aesthetically and creatively.
In summary, our project, focusing on the chewing gum issue, suggests a solution from both synthetic biology and hardware aspects. Our modeling projects have always been closely connected to wetlab work, optimizing the product and proving a success. We also ensure that our project is communicating to the world. Our integrated Human Practice projects help us hear stakeholders' voices, who offered lots of valuable and practical suggestions and ideas, pushing our projects forward. We also provided services to our community, letting people around us understand the charm of synthetic biology and the importance to protect the city environment.
References
[1]https://cul.sohu.com/20070822/n251713408.shtml
[2]Jensen, T.Z.T., Niemann, J., Iversen, K.H. et al. A 5700 year-old human genome and oral microbiome from chewed birch pitch. Nat Commun 10, 5520 (2019). https://doi.org/10.1038/s41467-019-13549-9
[3]https://en.wikipedia.org/wiki/John_B._Curtis
[4]https://m.jiemian.com/article/1551519.html
[5]https://www.bbc.com/zhongwen/simp/business-43303493
[6]http://news.sohu.com/18/95/news203719518.shtml
[7] Xiuli Peng. Research on the removal of urban dirt. Beijing University of Technology,2004.
[8] "CFR – Code of Federal Regulations Title 21". www.accessdata.fda.gov. Retrieved 15 December 2016.