Where our ideas come from: dioxin in our daily life
Dioxins are a group of toxic compounds, also are persistent environmental pollutants (POPs). Exposed in dioxin can lead to serious health damage, such as disrupting immune system, interfering with hormones, and causing cancer.
Burning anything composed of plastics could release dioxins. Dioxins could only be fully break down under the temperature higher than 850°C. Uncontrolled waste incineration and backyard burning give a high amount of dioxins emission. Realizing that dioxins are extremely dangerous, but are close to our lives, it raised our interest. Thus we went to Houli Refuse Incinerator Plant.
We found that the complex components of waste could lead to incomplete combustion and incomplete breaking down dioxins. The ash produced from burning waste might still contain dioxins. Then, the ash will be made into concrete product such as bricks, and eventually be placed back to our land.
Dioxin as a world problem: Vietnam War
When we keep on searching ideas about dioxin contamination in the soil, we found a historical tragedy about dioxin exposure that motivated us to dig into it.
During Vietnam War, the herbicide, Agent Orange was used by the U.S. military as a defoliant. Agent Orange contains TCDD, which is the most toxic of the dioxins. The use of Agent Orange has left serious and long-term health impacts upon the Vietnamese people and their offspring.
We went to Vietnam. We found the amount of contaminated land is very big. Subject to the lack of financial support, most of the land still remain contaminated.
The main problem: dioxin contaminated soil in large area of land
To find out possible solution to clear dioxin in large size of land, we looked into another case of dioxin contamination, China Petrochemical Development Corporation (CPDC) An-Shun site, located in Tainan City, Taiwan.
Before 1994, CPDC was run by the government of Republic of China. At that time, An-Shun site produced a large amount of sodium pentachlorophenol. Dioxins are by-products of sodium pentachlorophenol production. In 1994, after CPDC became a private corporation, the soil in CPDC An-Shun site was found been contaminated with dioxins. From then on, CPBC has been working for years clearing dioxin in the soil.
We visited CPDC An-Shun site. Among all the methods they are using, the “Heat Method” is the only one could be used to break down high concentration of dioxins in soil. The process of Heat Method, include digging out contaminated soil, and heat it up to over 850°C. It is very expensive, time consuming, and not ecofriendly.
Our method: Engineered Endophyte-Assisted Phytoremediation
We want to improve the current methods of clearing dioxin in the soil of large size of land. We aim to come out a more ecofriendly and more cost-efficient method. Accordingly, phytoremediation is our solution.
In former research, an endophyte, Burkholderia cenocepacia strain 869T2, has been isolated from the plant, Vetiver, in the contaminated land in Tainan. It was proved having the ability to break down TCDD.
But Burkholderia cenocepacia strain 869T2 is an opportunistic pathogen. On the other hand, Burkholderia phytofirmans strain PsJN is a plant growth-promoting rhizobacterium (PGPR) and has been thoroughly researched.
Thus, we came out an idea of synthesizing gene related to dioxin degradation to PsJN. So that we can create a better phytoremediation system, to clear dioxins in large size of land.
Future vision: eco-friendly and cost-efficient
From burning waste to Agent Orange, the current methods are either still leaving the contamination in land or being costly. In contrast, the method we introduced, Engineered Endophyte-Assisted Phytoremediation could solve the problem in an ecofriendly way.
We want to keep improving our iGEM project, and make it applicable for clearing large area of dioxin contaminated lands. We have shared our ideas of our project with China Petrochemical Development Corporation. They showed interest and encouraged us to keep working on our project.
Furthermore, the plant we used in phytoremediation has the potential to produce biofuels.
Last but not least, we think there should be many other possible applications for plant-microbe interactions. But, so far, there is not a lot of iGEM team focusing on this topic yet. Thus, we want to build up a model of engineered bacteria which can work together with the plant, especially on remediation of pollution. We hope our work could be benefit to iGEM competition and synthetic biology.