dye degrading bacteria isolation from textile industry soil

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