Plastics are in high demand in several industrial sectors, such as packaging, healthcare, fisheries, and agriculture, due to their enhanced physicochemical properties (Geyer et al., 2017). Recent plastic waste disposal solutions involve landfill, incineration, and recycling. However, landfill and incineration are undesirable as they result in environmental pollution and harmful effects on wildlife, damaging the environment and releasing toxicants (Oehlmann et al., 2009). On the other hand, recycled plastics are generally of inferior quality compared to the original, and some plastic recycling methods (waste-to-energy plants) involve incineration of plastic wastes to release energy, which could potentially emit toxic pollutants such as dioxins, acid gases, and heavy metals (Subramanian, 2019). Therefore, many of the current waste treatment practices are still far from ideal due to their harmful effects on the environment.
Along with the inadequacies in plastic waste management, the enormous increase in plastic waste production in recent decades is a problem of global concern. In 2018, the plastic waste generated reached 6.9 million metric tons (Mt) (Silva et al., 2020) and according to Geyer et al. (2017), approximately 24,000 Mt of plastic waste will be discarded in landfills by 2050. Moreover, small plastic fragments formed from plastic wastes (e.g., microplastics, nanoplastics) have accumulated in terrestrial and aquatic environments, which adversely affect the natural biota, agriculture, and fisheries, and posing serious health risks to humans.
Based on the serious threats that increasing plastic pollution is causing to the environment and human health, our iGEM project this year aims to design and construct an enhanced multi-plastic degrading bacterium that could potentially be used to reduce plastic waste to better protect our environment and human health. This project involves using computational modeling and in silico site-directed mutagenesis to change specific amino acid residues in two plastic-degrading enzymes - papain and polyurethane esterase (PueA) - to increase their binding affinity to plastic substrates. Based on the computational data obtained, we will design a bio-brick that contains genes encoding the mutant papain and PueA enzymes, and wild-type PETase, which will be used to construct an Escherichia coli clone (Plastilicious Coli) to develop an efficient multi-plastic bio-degradation system.
1. Geyer, R., Jambeck, J., & Law, K. (2017). Production, use, and fate of all plastics ever made. Science Advances 3 (7), e1700782.
2. Oehlmann J., et al. 2009A critical analysis of the biological impacts of plasticizers on wildlife. Phil. Trans. R. Soc. B 364, 2047–2062.
3. Silva, A., Prata, J., Walker, T., Campos, D., Duarte, A., Soares, A., . . . Rocha-Santos, T. (2020). Rethinking and optimizing plastic waste management under COVID-19 pandemic: Policy solutions based on redesign and reduction of single-use plastics and personal protective equipment. Science of the Total Environment 742, 140565.
4. Subramanian, M. N. (2019). Plastics Waste Management. Newark: John Wiley & Sons, Incorporated.