Microbial Decolorization of Triphenylmethane Dyes - Microbial Degradation of Synthetic Dyes in Wastewaters - page 168

particular dyes, the speci c chemistry and dosage of sorbents as well as some

physicochemical parameters such as pH, temperature and agitation. Biosorption is
effective, especially when the dye-containing ef

uent is very toxic and when
conditions are not favorable for the growth and maintenance of organisms. It tends
to occur reasonably fast and various waste materials including spent microbial
biomass can be employed as dyes adsorbents (Sharma et al. 2011 ). By developing
the methods of adsorbents regeneration, dyes recovery makes these processes more
economical (Won et al. 2006 ; Jasi ska et al. 2013 ). However, biosorption and sole

bioaccumulation do not eradicate the problem of dye pollution, because removed
compounds are not destroyed, but only entrapped by the adsorbent. Thus, bio-
degradation (biologically mediated breakdown of the chemical structure) seems to
be more suitable for dye removal (Kaushik and Malik 2009 ). Biodegradation
processes cause not only visible decolorization, but also result in the production of
intermediates usually not or less harmful as compared to parent compounds.
Sometimes, complete mineralization of dyes (conversion into CO 2 ,H 2 O, and/or any
other inorganic end products) can be achieved. Dyes biodegradation may be
mediated both by extracellular and intracellular enzymes. In the case of intracellular
biodegradation, the bioaccumulation is a primary mechanism of decolorization.
Recent

ń

ndings also indicate that in the TPM dyes elimination, non enzymatic, low
molecular weight compounds resistant to high temperature may also participate
(Gomaa et al. 2008 , Yan et al. 2009 ; Wang et al. 2011 ; Gomaa 2012 ). Also,
hydroxyl radicals produced by white and brown rot fungi during the Fenton-like
reaction Fe 2 þ þ þ OH are indicated as potential factors

involved in TPM dyes decolorization (Karimi et al. 2012 ; Moldes et al. 2012 ).
In recent years, a lot of studies have been focused on various organisms
(especially bacteria and fungi) capable of dyes degradation (Forgacs et al. 2004 ;
Kaushik and Malik 2009 ; Rodr

Fe 3 þ þ OH

H 2 O 2 !

guez-Couto 2009 ). The most widely studied TPM
dye-decolorizing microorganisms are white-rot fungi belonging to Basidomycota
(Levin et al. 2004 ). The strains of Phanerochaete chrysosporium are the most
popular basidiomycete models in the studies of synthetic dyes degradation.
Members of this genus are also known as good decolorizers of various TPM dyes,
such as Crystal violet, Pararosaniline, Cresol red, Bromophenol blue, Ethyl violet,
Malachite green, and Brilliant green (Radha et al. 2005 ; Gomaa et al. 2008 ; Gomaa
2012 ). However, members of other basidiomycete fungi have been also found to
remove TPM dyes. For example, Dichomitus squalens CCBAS 750 was proved to
be a good decolorizer of several chemically different synthetic dyes, including
Malachite green and Crystal violet (Eichlerov

í

et al. 2006a ). Casas et al. ( 2009 )
described effective elimination of Acid fuchsin, Brilliant green 1, Basic fuchsin,
Methyl green and Acid green 16 by Trametes versicolor ATCC 42530. Saparrat
et al. ( 2008 ) reported effective azo, heterocyclic and TPM dyes elimination by
Grammothele subargentea LPSC no. 436, a white-rot fungus from temperate and
tropical regions of America and East Africa. Despite a strong inhibition of growth
caused by TPM dyes, this strain eliminated Brilliant green, Crystal violet and
Fuchsin with high ef

á

ciency. According to Vasdev ( 2011 ), effective decolorization