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Textile dyes have highly stable structures, toxic properties and are resistant to the
degradation processes in the environment. The ability o f microorganisms to decolorize a wide
variety o f chemical compounds have been identified and exploited in various biotreatment
processes. The present study was carried out to study decolorization o f Cl Direct Blue 201
textile dye by bacteria which were isolated from wastewater collected near textile factories at
A vissaw ella and Pugoda, Sri Lanka. Wastewater samples were enriched under static
conditions by spiking the dye at a final concentration o f 50 mg L'1 for 14 days. Bacteria were
isolated using the Standard Pour Plate Method. The decolorization ability o f bacteria was
determined by introducing overnight starved equalized bacteria suspensions into filter
sterilized dye solutions at a final concentration o f 75 mg L'1. The flasks were incubated at
(28 ± I) °C under static conditions. Sub sample aliquots each o f 3 mL were removed at 2 day
intervals for a period o f 14 days. Standard spectrophotometric method was used to determine
the decolorization percentage. Among 35 bacteria isolates, five strains showed remarkable
decolorization o f the dye. Bacteria were tentatively identified by biochem ical tests and the
strains belonged to genera Pseudomonas, Bacillus, and Micrococcus. Decolorization
percentage were detected as 58.15 (± 0.92)% , 55.02 (± 0.70)% , 54.73 (± 1.99)%,
5 1.86 (± 0.49)% , and 5 1.55 (± 0.74)% for Pseudomonas sp. 2, Bacillus sp. 2, Pseudomonas sp.
I, Micrococcus sp., and Bacillus sp. 1, respectively. The highest dye decolorization percentage
(58.15% ) was recorded when Pseudomonas sp. 2 cell density was increased from 8 * 10
CFU mL’1 to 2.8 * I04 CFU mL'1. Other bacteria cell densities remained low and low
decolorization percentages were detected. Photolysis experiments revealed that decolorization
o f Cl Direct Blue 201 dye was not affected by sunlight. Thus, isolated bacteria can be used as
better candidates for removal o f Cl Direct Blue 2 0 1 textile dye as a green remedial solution.
