144
M. Dexilin et al.
only because of their colour but due to the lethal and carcinogenic properties of dye
compounds and their end products (Weisburger 2002).
Different approaches are available for the remediation of dye effluents which
include a number of physical, chemical and biological methods namely, oxidation and
reduction, adhesion, photocatalysis, coagulation, microbial degradation methods,
etc., (Fu and Viraraghavan 2001). Nevertheless, these technologies are usually ineffectual in the removal of color, costly and less adaptable to an extensive range of
dye waste waters (Banat et al. 1996). Biological methods are generally considered
environmentally approachable as they can lead to complete mineralization of organic
pollutants at low cost (Pandey et al. 2007).
Among the biological methods, bioremediation is promising tool for the elimination of toxic pollutants and it is the application of microorganisms (fungi, bacteria,
actinomycetes, yeasts and algae). Microorganisms which are naturally having the
tolerant ability to utilise dye compounds as their sole energy source are of extraordinary interest for scientific community to eliminate the environmental contaminants
that results from the industrial sources (Ali et al. 2010). Dye degradation by bacteria
predominantly depends on the enzymatic transformation where the azo dyes are
cleaved with the enzyme azo-reductase along with its coenzyme (Zimmermann et al.
1982; Moutaouakkil et al. 2003; Saroj et al. 2015), whereas fungal degradation of
azo dyes are catalyzed by extracellular enzymes ie., ligninolytic peroxidases (Young
and Yu 1997; Selvam et al. 2003; Máximo et al. 2003). Although bacterial dye degradation have been widely studied, in recent days fungal have gained importance in
dye degradation due to their unique extra cellular enzyme systems. Fungi are capable
of degrading the complex dye structures when compared with bacteria (Forss and
Welander 2009). Fungal mycelia have an additive advantage over single cell organism
by solubilizing the insoluble substrates by producing extracellular enzymes (Gajera
et al. 2015). Higher concentration of dye toxicants can be easily degraded by fungi
due to their advantageous enzyme arrangements and improved cell to surface ratio.
Various studies have reported that fungi like white rot decolorize the synthetic dyes
and the processes are mediated by lignin peroxidase (Ollikka et al. 1993), manganese
peroxidase (Heinfling et al. 1998) and laccase (Abadulla et al. 2000; Soares et al.
2001; Murugesan and Kalaichelvan 2003). Based on the fact that the fungi have the
capacity of degrading wide variety of organic and inorganic dye components, the
present study was carried out to isolate and screen fungal strains for decolorization
of azo dyes (AB 193 and AV 90) and optimize the pH and temperature for better
understanding the process.
M. Dexilin et al.
only because of their colour but due to the lethal and carcinogenic properties of dye
compounds and their end products (Weisburger 2002).
Different approaches are available for the remediation of dye effluents which
include a number of physical, chemical and biological methods namely, oxidation and
reduction, adhesion, photocatalysis, coagulation, microbial degradation methods,
etc., (Fu and Viraraghavan 2001). Nevertheless, these technologies are usually ineffectual in the removal of color, costly and less adaptable to an extensive range of
dye waste waters (Banat et al. 1996). Biological methods are generally considered
environmentally approachable as they can lead to complete mineralization of organic
pollutants at low cost (Pandey et al. 2007).
Among the biological methods, bioremediation is promising tool for the elimination of toxic pollutants and it is the application of microorganisms (fungi, bacteria,
actinomycetes, yeasts and algae). Microorganisms which are naturally having the
tolerant ability to utilise dye compounds as their sole energy source are of extraordinary interest for scientific community to eliminate the environmental contaminants
that results from the industrial sources (Ali et al. 2010). Dye degradation by bacteria
predominantly depends on the enzymatic transformation where the azo dyes are
cleaved with the enzyme azo-reductase along with its coenzyme (Zimmermann et al.
1982; Moutaouakkil et al. 2003; Saroj et al. 2015), whereas fungal degradation of
azo dyes are catalyzed by extracellular enzymes ie., ligninolytic peroxidases (Young
and Yu 1997; Selvam et al. 2003; Máximo et al. 2003). Although bacterial dye degradation have been widely studied, in recent days fungal have gained importance in
dye degradation due to their unique extra cellular enzyme systems. Fungi are capable
of degrading the complex dye structures when compared with bacteria (Forss and
Welander 2009). Fungal mycelia have an additive advantage over single cell organism
by solubilizing the insoluble substrates by producing extracellular enzymes (Gajera
et al. 2015). Higher concentration of dye toxicants can be easily degraded by fungi
due to their advantageous enzyme arrangements and improved cell to surface ratio.
Various studies have reported that fungi like white rot decolorize the synthetic dyes
and the processes are mediated by lignin peroxidase (Ollikka et al. 1993), manganese
peroxidase (Heinfling et al. 1998) and laccase (Abadulla et al. 2000; Soares et al.
2001; Murugesan and Kalaichelvan 2003). Based on the fact that the fungi have the
capacity of degrading wide variety of organic and inorganic dye components, the
present study was carried out to isolate and screen fungal strains for decolorization
of azo dyes (AB 193 and AV 90) and optimize the pH and temperature for better
understanding the process.