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intermediate compounds from sulfonated azo dyes, electro spray ionization (ESI)
source can be employed which causes minimal fragmentation of such dyes (Zhao
et al.
2007
; Lu et al.
2008
; Gomi et al.
2011
).
Apart from monitoring the dye removal process, the morphological changes in
fungal biomass can also be a useful aid in establishing the correlation between dye
removal process and the microbial agent present in the solution. Various micro-
scopic techniques, such as light microscopy, scanning and transmission electron
microscopy, may provide useful insights into the mechanism involved in the dye
removal process. Biosorption or bioaccumulation process by fungal biomass can
conclusively be explained through light microscopy techniques. Figure
2
shows the
phase contrast micrographs of Acid Navy Blue laden pellets of Aspergillus lentulus.
The size variation in the pellet structure, if any, resulting from various cultivation
conditions, such as nutrient sources, can also be visualized through microscopy
(Kaushik and Malik
2010b
).
Chakraborty et al. (
2013
) used light microscopy to show the biosorption of
Congo red dye on the biomass of Alternaria alternate. Also, SEM micrographs
were used by Chakraborty et al. (
2013
) to describe the amorphous nature of the
fungal biomass after dye removal process. Similarly, Transmission electron
microscopy can also be utilized to examine the difference obtained in the mor-
phological structure of the fungi prior to and after the biosorption of dye. Das et al.
(
2006
) demonstrated with the help of TEM micrographs that the cells of Rhizopus
oryzae in presence of Rhodamine B dye exhibit electron dense molecules mainly in
Fig. 2 Microscopic pictures of A. lentulus grown in different initial glucose concentrations: a 0%,
b 0.1 %, c 0.2 %, d 0.5 % and e 1 % on the pellet (Magnication: 10X) (Kaushik and Malik
2010b
)
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