Phoebe the Phoenix | iGEM 2025
Plastic pollution caused by the increasing use of non-biodegradable plastics has become a major global environmental concern, accumulating in landfills, oceans, and ecosystems, posing significant threats to wildlife, marine life, and even human health. Even when traditional recycling methods are applied, non-biodegradable plastics can degrade into microplastics: tiny plastic particles that contaminate water sources, enter food chains, and may carry harmful toxins.
One promising option is the use of biodegradable plastics, such as polyhydroxybutyrate (PHB), which have the advantage of breaking down naturally in the environment without releasing toxic residues. They offer a potential solution to reduce the long-term environmental damage caused by conventional plastics. However, despite their potential, PHB plastics are currently not as biodegradable in natural environments and are classified as biodegradable under industrial composting conditions. This limits their effectiveness as a truly sustainable alternative to conventional plastics, especially considering that plastic waste often ends up in uncontrolled, open environments where ideal decomposition conditions are absent.
As a result, while PHB represents a step toward more sustainable materials, it is not yet a fully effective replacement for conventional plastics. Continued research and innovation are needed to improve both its environmental performance and cost-effectiveness before it can serve as a viable large-scale solution to plastic pollution.
Our project focuses on the genetic engineering of Escherichia coli (E. coli) and Alteromonas macleodii to express novel depolymerase and dehydrogenase genes, to enhance the microbial degradation of PHB plastics. Engineered E.coli would allow degradation of PHB outside of marine environments, and although Alteromonas macleodii contains a natural PHB degradation pathway, we aim to see if this novel pathway provides any optimization. By enabling these organisms to express these key enzymes, we aim to significantly increase the breakdown efficiency of PHB, offering a potential biotechnological solution to mitigate plastic pollution.
Using our novel PHB depolymerase and dehydrogenase genes, we designed Level 1 (L1) plasmids intended for conjugation into Alteromonas macleodii knockout strains. These knockouts lack the native genes responsible for PHB degradation, allowing us to directly assess the efficiency of our newly identified enzymatic pathway in comparison to the wild-type strain.
A key objective of this phase is to demonstrate that the engineered knockout strains, when complemented with either our novel depolymerase or dehydrogenase genes, can grow using PHB as their sole carbon source. Successfully restoring this functionality would provide strong evidence for the activity and viability of our novel pathway, and support its potential for use in PHB recycling applications.
Results