Congo Red Decolorizing Bacteria from Paper Factory Effluent - Microbial Degradation of Synthetic Dyes in Wastewaters - page 142

as inoculants to degrade the Congo red dyes that are being used in some paper
factories or other factories using this kind of dye.
However, there is a need for further studies to con

rm other aspects of this
investigation. It has to be worked out whether the Congo red was completely
degraded and the degradation products be identi ed. If these microbes are used as

bioremediation inoculants, the amount of glucose utilized while degrading Congo
red should be determined and how its metabolism caused dye degradation in order
to optimize the decolorization process.
The exact location of the dye degrading enzyme inside the cell should be
determined using SDS-PAGE and the gel should be run with Congo red to deter-
mine the ability of the enzyme to degrade the said dye. Further this enzyme should
be puri ed and characterized for potential commercial applications.

Field application of the CRDB and consortia in dye polluted areas should be
conducted to test their ef

ciency as bioremediation inoculants for dye degradation/

decolorization.

8 Conclusion

Congo red is a carcinogenic direct diazo dye used for the coloration of paper
products. It is recalcitrant and usually found in ef uents of paper factories. Bacteria

in consortia and monocultures capable of decolorizing Congo red were also isolated
earlier. The consortia were labeled as IRRI-1 and S22. The monocultures were
labeled as SB13B, SB12D, IRRI-1C and S22B. The rate of decolorization by the
consortia was faster (1 week) than that of the monocultures (2 weeks to 1 month).
The 16S rRNA sequencing revealed identities of SB13B as E. coli, SB12D as
Enterobacter dissolvens and S22B as Pseudomonas citronellolis. API 20E identi-

ed IRRI-1C as Klebsiella oxytoca.
Dye degradation occurred in the supernatant of sonicated cells, indicating that
the dye degrading enzyme was located intracellularly. The enzyme capable of
reducing azo dyes was found to be present inside the cell of the four CRDB and was
released upon cell lyses, thus decreasing the absorbance of Congo red (decolor-
ization) as cell number increased.
The monocultures and consortia were able to decolorize Congo red in polluted
water, while no decolorization of the dye was observed in clean water. The resident
microorganisms together with other organic matter in the polluted water could have
caused dye degradation.
Toxicity tests of consortium- and monoculture-decolorized media and unde-
graded Congo red revealed that the test microorganisms used as bacteria and yeast,
were resistant to the toxic effects of Congo red. Toxicity tests on plants, however,
showed that undegraded Congo red was toxic to both rice and mung bean seedlings
and that the toxic effect on plants was reduced by decolorization. The monocultures
SB13B and S22B decolorized Congo red with concomitant nitrate reduction.