Microbial Degradation of Basic Dyes in Wastewaters - Microbial Degradation of Synthetic Dyes in Wastewaters - page 83

penetration (Walsh et al. 1980 ). Some of the basic dyes, such as crystal violet,
brilliant green, etc. are potent clastogens, which may promote tumor growth in
some species of

shes (Cho et al. 2003 ). In view of the recalcitrant nature of the
modern synthetic dyes there has been imposition of strict environmental legislation
in many countries. Conventionally, various physical and chemical treatment
methods are used for color removal from wastewater which includes chemical
coagulation, otation, precipitation, adsorption, ozonation,

photooxidation, irradiation, reverse osmosis, ion exchange and membrane

occulation, froth

ltration
(Banat et al. 1996 ; Srinivasan and Viraraghavan 2010 ). However, these methods
have limited use since they are very cost-intensive, face operational problems and
generate a large amount of solid waste, resulting in higher pollution load than the
ef nmez and Aksu 2002 ). On the other

hand, biological decolorization and degradation are environmentally friendly and
cost-competitive alternative to chemical decomposition (Robinson et al. 2001a ).
One key step to ef

uents and produce toxic by-products (D ö

cient dye degradation is to use broad-spectrum and highly

ef cient dye-decolorizing microorganisms. Further, the effectiveness of these

treatment systems depends on the survival and adaptability of microorganisms
during the treatment processes. Over the past decade, many microorganisms
capable of decolorizing basic dyes at laboratory scale level have been reported
(McMullan et al. 2001 ; Srinivasan and Viraraghavan 2010 ), but only a few reports
are available on their exploitation at treatment process level (Fu and Viraraghavan
2001 ; Kaushik and Malik 2009 ). Further, some studies also reveal that processes
using immobilized cells are more promising than free cells, as immobilization
allows repeated and continuous use of the microbial cells (Cassidy et al. 1996 ).

2 Microbial Treatment of Waste Water Containing Dyes

Phanerochaete chrysosporium is the most versatile, robust and model white-rot
fungus reported in the literature for decolorizing various basic dye-based waste-
waters (Knapp et al. 1995 ; Tatarko and Bumpus 1998 ; Gomaa et al. 2008 ; Faraco
et al. 2009 ). Earlier studies indicated that a few white rot fungi, like Phanerochaete
chrysosporium (Bumpus and Brock 1988 ) and Cyathus bulleri 195062 (Vasdev
et al. 1995 ), degraded Methyl violet, while Trametes hirsuta, Trametes gibbosa and
Trichaptum biforme (Eshghi et al. 2011 ) metabolized Methylene blue and Irpex
lacteus (Novotny et al. 2001 ) degraded Victoria blue. Jayasinghe et al. ( 2008 )
reported that white rot fungi, like P. cinnabarinus and G. lucidum, had the ability to
degrade approximately 80 % of the Methylene blue within 20 days, while C.
versicolor, F. fomentarius, T. suaveolens, S. ostrea and P. coccineus were able to
degrade only 40 % of the Methylene blue during same incubation period. Some
white rot fungi, like Phanerochaete chrysosporium, Pleurotus ostreatus, Coriolus
versicolor (Knapp et al. 1995 ), Pycnoporus sanguineus (Pointing and Vrijmoed
2000 ), Dichomitus squalens, Phlebia fascicularia, Phlebia

oridensis (Gill et al.
2002 ), Fomes sclerodermeus (Papinutti et al. 2006 ), Grammothele subargentea