Team:Hong Kong CityU/Implementation

Proposed Implementation

Purpose of Our Project

The environmental toll of plastic pollution is a sobering reminder for everyone to join concerted efforts to reduce plastic waste through sustainable means. With this intention in mind, our project aims to design and construct a multi-plastic degrading bacterium–the Plastilicious Coli–that could potentially be used to develop an effective technology to help reduce plastic waste and better protect our environment. We see our biosystem approach as a non-polluting process for plastic waste treatment.

Proposed End-users of Our Product

The proposed end-users of our product are industries involved in various plastic waste reduction and management technologies and businesses.

It is our conviction that our product can lead to a more environmentally friendly method for plastic waste treatment as the product will not produce any toxicants unlike the current plastic waste treatment methods such as incineration and landfill disposal which could give rise to bad odor, toxic by-products, leachate, and landfill gases. We intend to share this technique and strategy with companies, scientists, environmentalists, industries, and government bodies with a vested interest in using green and sustainable technologies to tackle the plastic waste problem that is adversely affecting the global environment.

Our Contribution to the Sustainable Development to Future Research

Environmental experts and scientists endeavour to look for an environmentally friendly approach to cope with the excessive accumulation of plastic wastes. Our project has simulated the native structure of polyurethanase esterase A (PueA) and predicted the polyurethane (PU)-binding site of the PueA and papain enzymes. We have also demonstrated the feasibility of employing in silico mutagenesis to increase the binding affinity of these enzymes with PU plastic as substrate. The data can be contributed to the Protein Data Bank for research purposes by future iGEM teams and research groups with interest in the enzymes of this project. Our findings have laid some groundwork for genetic modification of other plastic-degrading enzymes to develop an efficient plastic biodegradation system.

In our project, we have created 3 specific biobricks: part BBa_K3511000, a Papain G23W mutant; part BBa_K3511001, a PueA R329F mutant; and BBa_K3511002, an integrated PET- and PU-degrading enzyme biobrick for the iGEM registry. This information can be used by future iGEM teams to further explore and expand on the potential of using engineered enzymes to facilitate the biodegradation of plastic waste.

Our Proposed Implementation to the Real World

Our multi-plastic degrading bacterium, Plastilicious coli, can be tested to serve as a multi-plastic degrading agent in (1) natural environments and (2) controlled environments in the lab. According to PlasticEurope, agricultural fields are common plastic waste-contaminated areas as plastic materials are widely applied to remove weeds and for maintenance of optimal temperature for seed growth (1). A large amount of microplastic leftovers in the soil can lead to terrestrial and aquatic plastic pollution. Our Plastilicious coli can be directly seeded in agricultural lands for the bioremediation of PET (polyethylene terephthalate) and PU (polyurethane) microplastics as E. coli can survive and thrive in soil [MHCH1].

On the other hand, our team has great potential to cooperate with companies or institutions working on the utilization of plastic-degrading enzymes for bioremediation of plastic waste. Biotechnology companies such as CARBIOS, have been investing in a method to integrate plastic- degrading enzymes with polymers during plastic processing to facilitate degradation of used plastic polymers into base molecules that are assimilable by microorganisms. Our mutant enzymes, papain- G23W and PueA-R329F, may be useful to companies similar to CARBIOS to enhance the biodegradation of plastic waste generated by different manufacturing processes.


Figure1. Schematic drawing demonstrating the concept of enzyme degradable plastic by Carbios. Polymers and enzymes
are mixed together to form biodegradable plastics. The plastics produced will be decomposed after several days from their used dates

Safety Consideration in the Implementation of our Product

Our team has given special attention to the biosecurity risk that can be caused by our design. As our project involves the use of bacteria and genetic engineering technologies, the potential risk of the genetically modified bacterium to humans and its transmissibility in the environment must be assessed. The E. coli strain to be used is an attenuated laboratory strain and carries numerous mutations in its genome that preclude its ability to survive in the natural environment.

Our team has considered including in our design a kill-switch that would activate a toxin gene to kill off the host bacteria if it is transmitted to an undesired environment. The kill-switch will be driven by a gene promoter that is responsive to specific substrates. By doing so, we can control the survival and proliferation of the genetically-modified bug to specific environments such as plastic-infested landfills.

Potential Challenge and Further Studies to Implement our Product

Our Plastilicious coli is still at a very preliminary stage of development. Apart from safety concerns, more elaborate engineering and testing procedures will have to be carried out to improve and verify the plastic-degrading efficiency the Plastilicious coli under different environmental conditions.

Our team is proposing a study to incubate plastic filaments (PET and polyurethane) with the engineered bacteria to investigate the plastic degradation rate and capacity of the Plastilicious coli and its survival status in the environment. The plastic filaments will be visualized by SEM for surface corrosion, folding and fissure, which are the general end points used to assess successful degradation of a plastic substrate (Raaman et al., 2012).


1. Carbios. (n.d.). Biodegradation. Retrieved October 24, 2020, from
2. PlasticEurope. (n.d.). Plastics in Agricultural Applications. Retrieved from
3. Raaman, N., Rajitha, N., Jayshree, A., & Jegadeesh, R. (2012). Biodegradation of plastic by Aspergillus spp. isolated from polythene polluted sites around Chennai. J Acad Indus Res, 1(6), 313-316.

CityU HK IGEM 2020