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Project Overview

Azo dyes are the main synthetic colourant used in the industrial manufacture of a wide range of products such as clothing, upholstery, cosmetics, tattoo ink and more. These dyes are widely known to be safe and stable forms of synthetic colourants, however, when they are broken down in the guts of organisms they take on dangerous properties. In industry, leftover dye effluent is often not properly disposed of, or removed, during water treatment, which results in the accumulation of azo dyes in water bodies. It is at this point that these excess dyes are ingested, broken down, and excreted as products that have been found to be mutagenic and carcinogenic. Despite such toxicity, little to no effort has been made to dispose of these leftover azo dyes more responsibly.

Our iGEM project 2014 will work towards controllably degrading and detoxifying the excess azo dye effluent at the source - the textile factories - and filtering the different toxic breakdown products elsewhere, before they ever reach the water systems. Our aim is to then convert these products into innoculous, and potentially useful, chemicals that can be used in other processes. In effect, we want to recycle and re-use the excess azo dyes.

To do this will involve creating an enhanced azo dye decolourising organism by introducing the genes for three enzymes related to the degradation of these dyes: azoreductase, laccase, and lignin peroxidase into a host E.coli cell. In an industrial context, these three enzymes would work sequentially in a bioreactor of changing conditions. First, azoreductase will cleave the azo bond (N=N) by a double reduction using NADPH as a cofactor; this will produce a series of highly toxic aromatic amines. These compounds will be then oxidised by incorporation of lignin peroxidase and laccase, completing decolourisation and decreasing toxicity levels to the point that the final products of the process are less toxic than the intact dyes themselves. The complementary action of azoreductase and lignin peroxidase will be studied in order to find out the best possible approach of sequential reaction, and this core degradation module will be extrapolated to other areas such as BioArt projects and work on algal-bacterial symbiosis, trying to set up the foundations for a synthetic ecology.