Microbial decolourisation and degradation of textile dyes Abstract: Dyes and dyestuffs are widely used in various industries, with particular importance in textile manufacturing. Textile industry wastewater contains various pollutants, including dyes. Environmental legislation is increasingly being imposed to control the release of dyes, especially azo-based compounds. Microorganisms have long been known for their ability to decolourise and metabolise dyes, and bioremediation technologies for treating textile wastewater have attracted interest. This review investigates the mechanisms by which diverse microorganisms, such as white-rot fungi and anaerobic bacterial consortia, degrade dyestuffs. Introduction: Dyes and dyestuffs are widely used in the food, pharmaceutical, cosmetic, textile and leather industries. Over 100,000 commercially available dyes exist, with more than 7×10^5 tonnes of dyestuff produced annually. The health impact of dyes used in the food industry, especially azo dyes and their degradation products, has caused concern. Environmental and health effects of dyes released in textile industry wastewater are becoming subject to scientific scrutiny. Textile industry wastewater is a complex mixture of many pollutants, including organochlorine-based pesticides and heavy metals. During textile processing, inefficiencies in dyeing result in large amounts of dyestuff being lost to wastewater. The amount of dye lost depends on the type of dye used. Due to increasingly stringent environmental legislation, the textile industry is seeking effective wastewater remediation technologies, especially those that allow colour removal unaffected by conventional treatment systems. Despite the existence of various chemical and physical treatment processes, bioremediation is still seen as an attractive solution due to its low cost, environmental friendliness, and public acceptability. Actinomycetes, particularly Streptomyces species, are known to produce extracellular peroxidases involved in the biodegradation of lignin. These peroxidases are involved in the initial oxidation of lignin to produce various water-soluble polymeric compounds. Actinomycetes have also been shown to catalyse hydroxylation, oxidation, and dealkylation reactions against various xenobiotic compounds. The ability of actinomycetes to decolourise and mineralise textile dyes was initially investigated by three groups. Ball et al. screened 20 strains of actinomycetes for their ability to decolourise the polymeric dye Poly R. Only three of the 20 strains were observed to significantly decolourise the dye. Zhou and Zimmermann investigated the decolourising capabilities of 159 actinomycetes, with 83 isolates showing positive results. The finding that actinomycetes are capable of the aerobic decolourisation and degradation of azo dyes was significant given the recalcitrance of the compounds to degradation by other bacteria under such conditions.Microbial decolourisation and degradation of textile dyes Abstract: Dyes and dyestuffs are widely used in various industries, with particular importance in textile manufacturing. Textile industry wastewater contains various pollutants, including dyes. Environmental legislation is increasingly being imposed to control the release of dyes, especially azo-based compounds. Microorganisms have long been known for their ability to decolourise and metabolise dyes, and bioremediation technologies for treating textile wastewater have attracted interest. This review investigates the mechanisms by which diverse microorganisms, such as white-rot fungi and anaerobic bacterial consortia, degrade dyestuffs. Introduction: Dyes and dyestuffs are widely used in the food, pharmaceutical, cosmetic, textile and leather industries. Over 100,000 commercially available dyes exist, with more than 7×10^5 tonnes of dyestuff produced annually. The health impact of dyes used in the food industry, especially azo dyes and their degradation products, has caused concern. Environmental and health effects of dyes released in textile industry wastewater are becoming subject to scientific scrutiny. Textile industry wastewater is a complex mixture of many pollutants, including organochlorine-based pesticides and heavy metals. During textile processing, inefficiencies in dyeing result in large amounts of dyestuff being lost to wastewater. The amount of dye lost depends on the type of dye used. Due to increasingly stringent environmental legislation, the textile industry is seeking effective wastewater remediation technologies, especially those that allow colour removal unaffected by conventional treatment systems. Despite the existence of various chemical and physical treatment processes, bioremediation is still seen as an attractive solution due to its low cost, environmental friendliness, and public acceptability. Actinomycetes, particularly Streptomyces species, are known to produce extracellular peroxidases involved in the biodegradation of lignin. These peroxidases are involved in the initial oxidation of lignin to produce various water-soluble polymeric compounds. Actinomycetes have also been shown to catalyse hydroxylation, oxidation, and dealkylation reactions against various xenobiotic compounds. The ability of actinomycetes to decolourise and mineralise textile dyes was initially investigated by three groups. Ball et al. screened 20 strains of actinomycetes for their ability to decolourise the polymeric dye Poly R. Only three of the 20 strains were observed to significantly decolourise the dye. Zhou and Zimmermann investigated the decolourising capabilities of 159 actinomycetes, with 83 isolates showing positive results. The finding that actinomycetes are capable of the aerobic decolourisation and degradation of azo dyes was significant given the recalcitrance of the compounds to degradation by other bacteria under such conditions.