Microbial Degradation of Basic Dyes in Wastewaters - Microbial Degradation of Synthetic Dyes in Wastewaters - page 84

LPSC no. 436 (Saparrat et al. 2008 ), Trametes trogii and Trametes versicolor
(Levin et al. 2004 ; Casas et al. 2009 ) have been reported to degrade Brilliant green.
In addition to white rot fungi, other fungi, which were reported to decolorize and/or
adsorb basic dyes are Cunninghamella elegans (Cha et al. 2001 ), Aspergillus niger
(Fu and Viraraghavan 2002a ), Acremonium kiliense (Youssef et al. 2008 ) and
Rhizopus arrhizus (G l 2013 ). Apart from fungi, different bacteria, such as Bacillus

subtilis IFO 13719 (Yatome et al. 1991 ), Enterobacter cloacae MG82 (Jeong et al.
1998 ), Pseudomonas mendocina MCM B-402 (Sarnaik and Kanekar 1999 ),
Stenotrophomonas maltophila LK-24 (Kim et al. 2002a ), Sphingomonas paucim-
obilis (Cheriaa and Bakhrouf 2009 ), Rhizobium radiobacter (Parshetti et al. 2009 )
and Agrobacterium radiobacter (Parshetti et al. 2011 ) were also reported to degrade
Crystal violet, while Kurthia sp. (Sani and Banerjee 1999 ), Citrobacter sp. strain
KCTC 18061P (An et al. 2002 ) and Sphingomonas paucimobilis (Cheriaa and
Bakhrouf 2009 ) degraded Brilliant green (Table 1 ).
Algae are photosynthetic organisms, which grow in both fresh and salt water
habitats, and also identi

ü

ed as promising and potential biosorbent materials for
wastewater treatment, can very well compete with commercial biosorbents due to
their low cost, easy to culture, ready availability in large quantities and also display
a high adsorption capacity. The biosorption ability of algae is mainly attributed to
their high surface area and high binding af

ö

nmez and Aksu 2002 ). The
algal cell wall properties contribute to the biosorption process mainly due to
electrostatic attraction and complexation (Aksu and Tezer 2005 ). The biosorption
process is in

nity (D

uenced by various factors, such as initial pH, temperature, contact
time, initial dye concentration, biosorbent dosage, biosorbent particle size, bio-
sorption kinetics and isotherms. The initial pH in uences the biosorption process,

since it affects the adsorbate solubility and ionizing functional groups of algal cell
walls. It has been reported that alkaline pH is suitable for Malachite green removal
by microalga, Cosmarium sp. (Daneshvar et al. 2007 ). The isoelectric point (pI) of
the cell wall surface determines the adsorption ability. If the pH value is lower than
the pI value, the algal cell wall functional groups get protonated favoring anionic
dye removal and when the pI value becomes more negatively charged, it favors
adsorption of cationic dyes, due to electrostatic forces of attraction (Khataee et al.
2013 ). The algal cell wall matrix contains different functional groups, such as
hydroxyl, carboxyl, sulphate and other charged groups, which are generated by
complex heteropolysaccharides and lipid components which favor sequestration of
positively charged molecules, such as cationic dyes from wastewater (Mohan et al.
2002 ; Daneshvar et al. 2012 ). The dye removal by algae is due to the accumulation
of dye ions on the surface of algal biopolymers and further diffusion of the dye
molecules from aqueous phase onto the solid phase of the biopolymer (

zer et al.
2006 ). Extracellular polymers consist of surface functional groups, which enhance
sorption of the dye molecules onto the surface of the polymer (

Ö

oc) and settle
during the dye removal process. This phenomenon is known as biocoagulation
which is mainly due to the release of metabolic intermediates (long chain bio-
polymers) by algae having good coagulation ability towards the dye remaining in
the wastewater (Mohan et al. 2002 ) (Table 2 ).