Decolorization of a dye solution by bacteria could be
due to adsorption to microbial cells or to biodegradation.
In adsorption, examination of the absorption
spectrum would reveal that all peaks decreased approximately
in proportion to each other. If dye removal is
attributed to biodegradation either the major visible
light absorbance peak would completely disappear or a
new peak would appear. Dye absorption would result in
cell materials, which are deeply coloured because of
adsorbed dye, whereas those retaining their original
colours are accompanied by the occurrence of biodegradation
[20]. In this study the abiotic decolorization
studies with autoclaved, dead E. coli cells showed that
no significant colour removal were observed under
anaerobic conditions for DB 38 and CR dyes. In
addition, as the DB 38 and CR levels were reduced,
the broth media returned to its original yellow/white
colour. The absorbance peak at 520 nm completely
disappeared after cultivation for decolorization of DB
38. In other words, when comparing the UV/VIS scans
of dye and incubated dye samples it was observed that
the aforementioned spectra were different, suggesting