MICROBIAL DEGRADATION OF TEXTILE
DYES
AIM:
To
demonstrate the microbial degradation of textile dyes
PRINCIPLE:
Pollution
due to textile industry effluent has increased during recent years. Moreover,
it is very difficult to treat textile industry effluents, because of their high
Biological Oxidation Demand (BOD), Chemical Oxygen Demand (COD), heat, color,
pH and the presence of metal ions. The traditional textile finishing industry
consumes about 100 liters of water to process about 1 Kg of textile material.
The new closed-loop technologies such as the reuse of microbial or enzymatic
treatment of dyeing effluents could help reducing this enormous water pollution.
Azo dyes have been used increasingly in industries because of their ease and
cost effectiveness in synthesis compared to natural dyes. However, most azo
dyes are toxic, carcinogenic and mutagenic. Azo bonds present in these
compounds are resistant to breakdown, with the potential for the persistence
and accumulation in the environment. However, they can be degraded by bacteria
under aerobic and anaerobic conditions. Bioremediation through microorganisms
has been identified as a cost effective and environment friendly alternative
for disposal of textile effluent. A wide variety of microorganisms are reported
to be capable of decolonization of dyes. The current study has conducted the
potential of isolated bacterial strain from textile effluent for their
decolorization efficiency of the textile dyes, under in vitro conditions and
optimization of the factors influencing the process.
MATERIALS REQUIRED:
Nutrient
agar, textile dyes, inoculation loop, Petri dishes, conical flasks, pipettes,
Incubators.
PROCEDURE:
1.
The
textile effluent was collected in sterile collection tubes from the sludge and
wastewater of the ditches at industrial site.
2.
The sample collected from the textile mill was screened for dye decolorizing
bacterial strains by inoculating 10 ml of sludge solution into 250 ml
Erlenmeyer flask containing 100 ml nutrient broth.
3.
The flasks were incubated at 37°C under shaking conditions (120 rpm). After 48
h of incubation, 1.0 ml of the culture broth was appropriately diluted and
plated on Nutrient Agar containing 100 mg L–1textile dye.
4.
The Morphologically distinct bacterial isolates showing clear zones around
their colonies due to decolorization of dye were selected for further studies.
5.
The Screening process in liquid media was carried out by inoculating a loop
full of cultures exhibiting clear zones into Nutrient broth containing textile
dye under static conditions.
6.
After 24 h of incubation, 1ml. of cell suspension was transferred to fresh
nutrient broth containing textile dye to screen the strains with color removing
ability.
7.
The Screening procedure in liquid medium was continued until complete
decolorization of broth.
8.
The bacterial isolate which tolerated higher concentration of the azo dye was
isolated by streak plate method. The azo dye decolorizing bacteria was
identified from several aspects including morphology characters, biochemical
tests as described in Bergey’s manual of determinative bacteriology.
RESULT:
Colonies
surrounded by a nearly decolorized zone were isolated as positive and those
organisms not able to form zone were considered as negative.
 |
| clear zone formation around the bacterial colonies |
