Project Overview

The Problem: Azo Dyes in the Environment

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.

The Solution: Goodbye AzoDyes, UCL iGEM Team 2014

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.

Using Synthetic Biology

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.

Implementation in Industry

In the textile industry today, annual production of dyestuff amounts to millions of tons globally. Azo dyes represent two thirds of this value, a majority of which find their way to wastewater.

Our idea is to conceive an integrated end-of-pipe method for detoxifying effluent streams of dye factories. The goal is to achieve a two-stage regimen in sequence to ensure optimal conditions for the degradation of azo dyes within a batch bioreactor system. This would be an attractive and effective approach to dealing with azo dye contamination of the environment. As a financial incentive, we are also looking at maximizing the profitability of various potential breakdown products. As a lucrative continuous-process alternative, we are investigating the application of microbial fuel cell technology to an aerobic bioreactor system, for simultaneously detoxifying azo dyes and generating electricity.

Considering the potential for scalability, this method would present various economic and environmental advantages for industries that generate large amounts of dyestuff. This could also be spinned to become a modular bioprocess method for wastewater treatment of other toxic, normally recalcitrant chemicals.

Recycling Azo Dyes

Depending on the azo dye that is being degraded, different sets of breakdown products can be produced. Once degraded, each of the different compounds will be identified and separated. We have three potential avenues for re-using these products: (1) converting functional groups on the aromatic amines into simple aromatic fragrances; (2) isolating and diverting nitrogenous compounds to algae, which can form, and maintain, a symbiotic relationship with the dye-degrading E. coli hosts; (3) selling more complex compounds to pharmaceutical companies for the production of drugs.

BioArt

Keep an eye on this space as we have lots of fun things in the works coming up soon!