Abstract
Several species of white-rot fungi were investigated for their utility in prolonged decolouration of the recalcitrant sulfonated azo dye, amaranth. Trametes pubescens, T. multicolor, T. meyenii and T. versicolor decoloured amaranth azo-dye best on low-nitrogen agar-solidified media whereas Bjerkandera adusta and Phlebia radiata were most effective in low nitrogen medium supplemented with manganese. Trametes cotonea did not decolour effectively under any condition. The decolouring Trametes species were also effective in liquid culture whereas B. adusta and P. radiata were not. Trametes meyenii, T. pubescens and T. multicolor were equal to or better than commonly employed T. versicolor at decolouring amaranth. This is the first study to show the dye decolouration potential of T. meyenii, T. pubescens, and T. multicolor. Supplementing with Mn(II) increased assayable manganese peroxidase activity, but not long-term decolouration, indicating that laccase is the main decolourizing enzyme in these Trametes species. This appears to be because of inadequate Mn3+ chelation required by manganese peroxidase because adding relatively low amounts of malonate enhanced decolouration rates. The ability of Trametes meyenii to simultaneously decolour dye over prolonged periods of time while growing in relatively nutrient-rich medium appears to be unique amongst white-rot fungi, indicating its potential in wastewater bioremediation.
Highlights
One of the largest sources of environmental pollutants is the textile industry, which can produce over 800 kilo tonnes of dye annually, with 90% of the waste discharged into the environment (Nigam et al 2000; Hessel et al 2007; Martin et al 2012)
In the current study we investigate white-rot fungal species, including five species of Trametes, to determine how well they degrade amaranth and produce Manganese peroxidase (MnP) and laccase in response to different nutritional treatments
This is corroborated by the lack of detectable MnP and laccase activities in these species (Figure 2)
Summary
One of the largest sources of environmental pollutants is the textile industry, which can produce over 800 kilo tonnes of dye annually, with 90% of the waste discharged into the environment (Nigam et al 2000; Hessel et al 2007; Martin et al 2012). They employ relatively non-specific enzymes that are able to Manganese peroxidase (MnP) is the most common ligninolytic peroxidase as it is produced by almost all white-rot basidiomycetes (Morgenstern et al 2008; Tomsovsky et al 2009), and laccase occurs in almost all wood- and littertransforming basidiomycetes (Wesenberg et al 2003) These enzymes play major roles in decolorization processes in the fungal genus Trametes where they can be expressed to some degree under primary as well as secondary metabolism (Libra et al 2003). Because of their common occurence and enzyme efficiencies (Morgenstern et al 2008; Wesenberg et al 2003; Tomsovsky et al 2009) and the fact that normal culture conditions for fungi do not induce lignin peroxidase activity (Swamy and Ramsay 1999b), enzyme investigations were limited to MnP and laccase in this study
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