Decoloration of industrial dye effluents using immobilized lignin degrading enzymes

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Colored effluent into the environment is of growing concern, as color is a visible pollutant which is increasingly being regulated worldwide. It is aesthetically unpleasing, negatively impacts the environment and some synthetic dyes may be carcinogens or mutagens. Such effluents arise from textile and dyestuff manufacturing, and the pulp and paper, and food processing industries. Most current physical and/or chemical decoloration technologies do not achieve total decoloration, have operational difficulties or are too expensive; and traditional biological wastewater treatments have low removal efficiencies. White rot fungi can decolorize a wide range of dyes. Although there are advantages to use immobilized cultures, increase in biofilm growth eventually lead to poor reactor performance. Using their enzymes will avoid this problem but soluble enzymes are not practical in treating effluents as large quantities would be needed and the enzymes could be denatured. Immobilization on a solid matrix could overcome these drawbacks. So far, we have successfully evaluated immobilized laccase but white rot fungi produce other lignin-degrading enzymes such as lignin peroxidase, manganese peroxidise and cellobiose dehydrogenase that also decolorize. To have an effective process, combinations of these enzymes are required. The long-term objectives of this proposal are (i) to develop a cost-effective, biological process (based on immobilized enzymes) to decolorize dye effluents and (ii) to understand the degradation mechanisms. The first objective will be achieved by combining enzymes to target azo and anthraquinone dyes which make up a majority of dyes commercially used. The second objective will focus on the role of surfactants in decolorization as this effluent component causes significant enzyme inhibition. The knowledge from this work can also be applied to the degradation of other xenobiotics and biobleaching of pulp and paper. The outcome of this project may contribute to the Canadian economy by creating jobs in the construction and operation of enzyme reactors for wastewater treatment; and improve the quality of life and the environment by removing a visible and potentially toxic pollutant.