Team:UCL

University College London, iGEM Team 2014 - Goodbye Azo Dye!

The World Problem:

Azo dyes are the main synthetic chemical colourant used in the industrial manufacture of a wide range of products, such as clothing, cosmetics, tattoo ink, food, and more. These compounds are generally considered to produce safe and stable forms of dyes, which is why dye companies predominantly use azo dyes to colour their products. However, in some (textiles/dye) industries, leftover dye effluent is often not adequately disposed or removed during water treatment, which can result in the accumulation of azo dyes in water bodies. It is at this point that azo dyes can be ingested, broken down, and excreted as potentially toxic (mutagenic or carcinogenic) aromatic amine products. Removing azo dyes in a sustainable manner remains a major challenge, both for the developing world and industrialised nationals.

Our Synthetic Biology Solution:

In response to this challenge, the project for the UCL iGEM Team 2014 is to design, model, and construct an engineered Azo-Remediation Chassis (ARC) with BioBrick Parts that are:
a) capable of sensing environmetal levels of azo compounds/dyes;
b) efficent at degrading, and decolourising, these azo compounds;
c) and able to utilise the azo dye breakdown products as substrates to build high-value fine chemicals. Welcome to project, "Goodbye Azo Dye"!

The General Approach:

To validate the above approach, we will first introduce genes encoding three sequentially-acting enzymes (azoreductase, laccase, and lignin peroxidase) into a host E. coli cell. These transformed E. coli cells will then be introduced to a mixture of azo dyes (emulating wastewater).
Stage 1: Azoreductase will cleave the azo bond (N=N) by a double reduction, using NAD(P)H as a cofactor; a series of highly toxic aromatic amines will be produced.
Stage 2: The breakdown products of Stage 1 will then be oxidised by laccase and/or lignin peroxidase, which will complete the azo dye degradation, as well as result in a decolourisation of the azo dye solution.

This sequential degradation process should result in a decreased toxicity level of the azo dye mixture, to the point that the final products of this process are less toxic than the intact dyes themselves. The complementary action of the azoreductase and laccase and/or lignin peroxidase will be studied, both experimentally and through modelling, in order to find the best possible sequential approach.

Finally, this core degradation module will be extrapolated to other areas, such as BioArt projects and work on algal-bacterial symbiosis, to try set up the foundations for synthetic ecology.

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