Team:NTHU Taiwan/Description
Introduction
What’s the problem?Perfluorinated chemicals (PFCs), including PFOA (perfluorooctanoic acid) and PFOS (perfluorooactanesulfonic acid), are hazardous man-made chemicals produced or used in industry and daily necessities. Due to strong binding energy of carbon-fluorine bond, these compounds are very difficult to be degraded in nature and they also accumulate in organism, causing harm to the environment and human.
Since there’s no regulation for banning PFCs usage and emission in most countries all over the world nowadays, environmental organizations, government and scientists have discovered liquid and volatile PFCs distribution in waters, in snow, in the air, and even in drinking water. Besides, tons of researches show that PFCs potentially cause diseases to animals and human.
High concentration of PFCs have been detected in Pearl River and Yangtze River in China and some lakes in USA since 2007.[1] In 2010, southern catfishes and carps in the Yangtze River were found with exceed concentration of PFCs in the liver.[2] In USA, Environmental Working Group (EWG) even showed statistics of PFCs pollution levels in every state.[3]
PFOA, one of the most studied PFCs, has been detected in adults' bodies around the world.[4] Because of its hydrophobicity, PFOA can stay in human body for a long time.
Groups of Scientists conducted researches on animals and found that animals which were fed with PFOA, end up with their thymus, spleens, and livers enlarged, possibly tumorous.[6] From several epidemiological studies conducted on population that is exposed to PFOA, researchers discovered that PFOA has probable link to high cholesterol, ulcerative colitis, thyroid disease, testicular cancer and kidney cancer.[7]
How do we solve the problem?In our project, we focus on degrading a class of PFCs, PFOA (perfluorooctanoic acid). Traditionally, electro-thermal and burning processes are used to decompose PFCs; However, these processes are not sustainable. Therefore, we hope to develop an efficient and eco-friendly method to keep the world from PFCs disaster.
Our goal is to break carbon-fluorine bonds in PFOA.
Fac-dex, which is under the category of Fluoroacetate Dehalogenase, has the ability to cause C-F bond cleavage. The predicted reaction mechanism of Fluoroacetate Dehalogenase is shown below.[8]
On the other hand, some papers show that Burkholderia sp. FA1 and Pseudomonas fluorescens are able to degrade PFOA producing fluoride. Additionally, both kinds of bacteria contain fac-dex gene. Hence, we assumed that fac-dex is the key to degrading PFOA.
In the process breaking C-F bond, fluoride will be released. We also insert a fluoride transporter gene, CRCB[9], to help our modified E.coli survive.
There are two goals in our experiment: Degradation of PFOA and transportation of fluoride. We design a series of experiments for these targets.
We showed the details of experiment in Experiment.
Reference[1] River, Y. (2010). Swimming in Chemicals.
[2] Thorup, K., Raaschou-nielsen, O., Sørensen, M., Roursgaard, M., Loft, S., & Møller, P. (2010). Mutation Research / Genetic Toxicology and Environmental Mutagenesis Genotoxic potential of the perfluorinated chemicals PFOA , PFOS , PFBS , PFNA and PFHxA in human HepG2 cells. Mutation Research - Genetic Toxicology and Environmental Mutagenesis, 700(1-2), 39–43.
[3] Environmental Working Group (EWG)
[4] http://toxsci.oxfordjournals.org/content/99/2/366.full.pdf Table 3
[5] http://toxsci.oxfordjournals.org/content/99/2/366.full.pdf Table 5
[6] 3M Company. (2003). Environmental and health assessment of perfluorooctanesulfonate and its salts.
[7] Perfluorooctanoic Acid (PFOA) Exposures and Incident Cancers among Adults Living Near a Chemical Plant (author: Vaughn Barry, Andrea Winquist, and Kyle Steenland)
PFOA probable link with cancer
PFOA probable link with thyroid disease
PFOA probable link with heart disease
PFOA probable link with autoimmune disease
[8] Ji-Quan Liu, Tatsuo Kurihara, Susumu Ichiyama, Masaru Miyagi, Susumu Tsunasawa, Haruhiko Kawasaki, Kenji Soda, and Nobuyoshi Esaki (June 22, 1998) THE JOURNAL OF BIOLOGICAL CHEMISTRY Vol. 273, No. 47, Issue of November 20, pp. 30897–30902, 1998
[9] Sequence source
Genome sequence of MG1655
Sequence on NCBI
