Degradation of Anthroquinone Dyes Stimulated by Fungi - Microbial Degradation of Synthetic Dyes in Wastewaters - page 340

strains. To be used as a carbon source, certain bonds in the dye molecule are
cleaved, but the chromophore is not affected. This mechanism occurs generally in
the case of consortium of microorganisms (Knapp et al. 2001 ; Singh 2006 ).

5 Factors Affecting Fungal Decolorization
and Degradation of Dyes

There are various factors, such as media composition, pH value, agitation and
aeration, temperature and initial dye concentration, which can impact the growth of
fungal strains and also regulate decolorization and degradation of synthetic dyes.

5.1 Media Composition

The media composition plays a very important role in facilitating the fungal growth
and decolorization process. The media usually contain carbon and nitrogen sources
along with mineral nutrients and other additives (Singh 2006 ).

5.2 Carbon Source

There is an essential requirement of carbon source for the fungal growth, as it
supplies the oxidants which mediate the decolorization of dyes. Generally glucose
has been widely used by many workers as a carbon source in their studies for the
fungal culture. Besides, sucrose, maltose, xylose and glycerol, starch and xylan
were also found to be useful as a carbon source. But cellulose and its derivatives
were not found effective as a source of carbon. For initial experiments, glucose at
concentration of 5

10 g l − 1 is a good choice. A wide difference in the nature of
carbon substrates used for the ef

-

uent treatment of the dyes was observed. It was

found that ef uents from dyeing or chemical dye production usually do not contain

usable carbon substrates, while others from distilling or paper pulping contain a
range of carbohydrates which are useful substrates for certain white-rot fungi. So,
the addition of carbon source largely depends on the organism and type of the dye
to be treated for decolorization/degradation.
Swamy and Ramsay ( 1999b ) observed that glucose was an essential carbon
source and a minimum of 0.34 g glucose l − 1 was required for the decolorization of
dyes. In addition to being a potential carbon and energy source, glucose is also a
substrate for pyranose oxidase which can generate H 2 O 2 (Giffhorn 2000 ) for per-
oxidase activity and oxygen radicals.