Degradation of Anthroquinone Dyes Stimulated by Fungi - Microbial Degradation of Synthetic Dyes in Wastewaters - page 341

Radha et al. ( 2005 ) have also investigated the role of glucose in the decolorization
of dyes. It was noted that when the initial concentration of glucose was enhanced
from 1 to 5.0 g l − 1 in the basal medium, the decolorization of dyes was signi

cantly
enhanced. This clearly indicates that glucose enhances the decolorization of dyes
and a concentration of 5.0 g l − 1 glucose was found to be suf cient to achieve the

maximum decolorization. It was also noted that as the glucose concentration was
increased from the optimal level, it caused a decrease in dye decolorization rate due
to change in the metabolic pathways. In such situation, glucose was more utilized for
the growth of fungus than for decolorization of dyes.

5.3 Nitrogen Source

Nitrogen is a second essential component of media required for the growth and
enzyme production in fungal species. Therefore, the demand of nitrogen varies
widely among fungal species. For example, in P. chrysosporium, the ligninolytic
enzymes are produced under nitrogen-limited conditions, while in B. adusta, more
LiP and MnP are produced in nitrogen-suf

cient media. However, white-rot fungi
have the ability to use both inorganic and organic nitrogen sources. Ammonium
salts in the form of inorganic nitrogen are generally used for the fungal growth and
enzyme production, while organic nitrogen is not found suitable. Therefore, the
presence of usable nitrogen source in the case of ef uent treatment should be

considered from the angle of dye decolorization.
Radha et al. ( 2005 ) studied the effect of nitrogen source on decolorization of
dyes. In their study, the ammonium chloride was chosen as nitrogen source (0

0.2
gl − 1 ) Without nitrogen source, the decolorization of dyes was found to be 45 %,
but when medium was supplemented with 0.05 g l − 1 of ammonium chloride, the
dye decolorization was attained to 96 %. However, when the amount of nitrogen
source was increased from its optimum level, the decolorization processwas
adversely affected. However, Swamy and Ramsay ( 1999a ) have reported that
production of manganese peroxidase (MnP) and laccase enzyme was enhanced in
nitrogen-limited conditions duringdye decolorization.

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5.4 Mineral Nutrients

In addition to carbon and nitrogen sources, certain mineral nutrients are also required
by microbes, for example, white-rot fungi need iron, copper and manganese for the
decolorization of dyes. These mineral nutrients can be either a part of ef

uent or
must be added to the media. In addition, fungal lignin peroxidase requires a variety
of other materials, like veratryl alcohol, tryptophan and aromatics (phenol and
aniline) for its activity, as these serve a low molecular mass redox mediators and
therefore, facilitate the decolorization process (Knapp et al. 2001 ; Singh 2006 ).