IGEM:Stanford/2009/Plastic Degradation
Project Summary
Can we convert environmentally hazardous phenols and formaldehyde (the primary components of a class of widely used resins) into a carbon source for E. coli?
Original Presentation: Tough Plastic: Degrading Phenol Resins
What We Know
Previous research has focused on characterizing organisms that are shown to degrade phenol or formaldehyde:
Tsai et al. isolated a strain of yeast capable of degrading both phenol (meta-fission) and formaldehyde, but acknowledged that “a microbe with a biodegrading power toward phenol and formaldehyde concurrently has been scarcely reported.”
- Tsai SC, Tsai LD, and Li YK. An isolated Candida albicans TL3 capable of degrading phenol at large concentration. Biosci Biotechnol Biochem. 2005 Dec;69(12):2358-67. DOI:10.1271/bbb.69.2358 |
Gusse et al. isolated white-rot fungus capable of degrading phenolic resins but efficiency uncertain. (Gusse et al. 2006)
Hidalgo et al. showed the ability of Rhodococcus erythropolis UPV-1 to grow on phenol and remove formaldehyde.
However, most research has described organisms that can degrade one or the other. Introducing both pathways into a genetically tractable and well-studied organism like E. coli would not only combine pathways in a useful way from an environmental standpoint but it would also leave ourselves and others more room to alter these pathways to make them more efficient.
What We Don't Know (but need to know)
Experiment Ideas
Potential subprojects:
1. Phenol Degradation: Goal: Engineer E. coli to metabolize phenol as a carbon source, linking it to cellular respiration
To achieve this, we would need to transduce genes (already in the database in PubMed) from some type of fungus or bacteria (such as Pseudomonas aeruginosa AT2, Burkholderia cepacia PW3, or Aspergillus fumigatus ATCC 28282) into E. coli via a plasmid vector. Our choice of genes will depend on whether we decide to introduce enzymes responsible for meta- or ortho- phenol metabolism. The former will result in byproducts that are used in glycolysis; the latter will yield intermediates of the TCA cycle.
2. Formaldehyde Degradation Goal: Engineer E. coli to metabolize formaldehyde as respiration precursor, bypassing the detoxification pathway
This would require introducing genes for two enzymes (3-Hexulose-6-Phosphate Synthase and phospho-3-hexuloisomerase) into the E. coli genome through a plasmid vector to introduce the pathway necessary for formaldehyde assimilation. Also, we would have to control the formaldehyde oxidation pathway in E. coli, which detoxifies formaldehyde but does not assimilate it into biomass as a carbon source, either by knocking out or downregulating expression of the genes involved in this pathway.
Important/Interesting Papers
Phenol (and Formaldehyde) degrading Yeast
White rot fungus degrades phenolic resins This article also describes a way of preparing phenolic resins that might be useful to us. The efficiency of degradation of these white rot fungus is uncertain.
Questions/Discussion
Is it possible to make phenol and formaldehyde the sole carbon source for E. coli? Would there be any way to compartmentalize phenol or formaldehyde degradation, using previous iGEM work on creating a synthesome? Would there be any crosstalk between the pathways for formaldehyde and phenol degradation that would harm the cells?
