Team:SJTU-BioX-Shanghai/Project/project2.3

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Revision as of 13:03, 22 October 2012

Membrane Accelerator - PAH degradation & DBT desulfurization

  • State of the art

Natural biodegradation is a very slow process but indispensible in environment restoration. Previous scaffold system has been used to accelerate biosynthetic pathway. This year, iGEM team SJTU-BioX-Shanghai is trying for the first time to recruit scaffold system to accelerate biodegradation pathway. It offered a new direction in the application of scaffold system.

  • Aims

To testify the feasibility of Membrane Accelerator in Biodegradation Pathway

To accelerate degradation of Polycyclic Aromatic Hydrocarbon (PAH)

To accelerate degradation of Dibenzothiophene (DBT) desulfurization


  • Achievements

A novel concept is proposed to apply scaffold system to facilitate biodegradation pathway

Two well-studied biodegradation pathways are selected, which could potentially benefit environment restoration


Background

Polycyclic aromatic hydrocarbons (PAHs), which consist of two or more fused aromatic rings, are widespread in the environment and persist for a very long time. Some PAHs are toxic, mutagenic and carcinogenic and therefore are health hazards. Efforts have been made to screen bacteria strains that could degrade PAH. Moreover, many researchers focused on studying the mechanism of PAH biodegradation. But the rate of natural biodegradation is relatively slow. Team SJTU-BioX-Shanghai is trying to build a Membrane Accelerator to speed up biodegradation rate of PAH biodegradation process. Naphthalene degradation pathway in Pseudomonas species is well studied and thus recruited in our project to build Membrane Accelerator for PAH biodegradation.

Degradation Pathway

We recruited naphthalene degradation pathway in Pseudomonas species, which has been well characterized. Six crucial enzymes are involved in naphthalene degradation pathway.

Demonstration of naphthalene degradation pathway in Pseudomonas species

In the first catabolic step, an oxygen molecule is introduced at the 1,2-position of the aromatic nucleus to produce cis-1,2-dihydroxy-1,2-dihydronaphthalene by naphthalene dihydrodiol dioxygenase. cis-1,2-Dihydroxy-1,2-dihydronaphthalene is then dehydrogenated to 1,2-dihydroxynaphthalene by cis-naphthalene dihydrodiol dehydrogenase. 1,2-Dihydroxynaphthalene is cleaved by 1,2-dihydroxynaphthalene dioxygenase, and the resulting ring-cleavage product spontaneously cyclizes to form 2-hydroxy-2H-chromene-2-carboxylic acid. Enzymatic reactions by an isomerase and a hydratase-aldolase result in the production of salicylaldehyde, which is then transformed to salicylate by salicyladehyde dehydrogenase.

Design

To test whether Membrane Accelerator could accelerate naphthalene biodegradation pathway, we are trying to link six enzymes in this pathway to orderly organized membrane anchor and expressed them in E.coli. E.coli expressing the same type and amount of cytoplasmic enzymes is set as control group.

Demonstration of Membrane Accelerator designed for speeding naphthalene biodegradation process


Biodesulfurization of Dibenzothiophene (DBT)

Reference