Biodegration of Textile Dyes Using Bacteria



10,000 dyes and pigments are produced annually worldwide amounting to 7x105 tones which are hazardous and pose serious environmental problems. It is estimated that 10-15% of the dye is lost n the effluent during the dying process. The recent high profile of color pollution is mainly the result of increasing public awareness and expectations of the environment; coinciding with rising levels of color discharges. One of the more pressing environmental problems that have been facing the textile industry is the removal of the color from dye bath effluent prior to discharge to local sewerage treatment facilities or adjoining watercourses. Considerable efforts have been made on developing suitable treatment systems for these effluents. Only biotechnological solutions can offer complete destruction of the dyestuff with a co-reduction in the biological oxygen demand (BOD) and chemical oxygen demand (COD).

Wastewaters originating from reactive dye processes have created a particular problem because the dyes can exhibit low levels of fixation with the fiber. The brightly colored unfixed dyes are highly water-soluble and are not removed by conventional treatment systems. This is particularly noticible as the human eye can detect reactive dyes at a concentration as low as 0.005 mg/l in clear waters. Discoloration of textile dye effluent does not occur when treated aerobically by municipal sewerage systems. Though the formation in 1974 of the Ecological and Toxicological Association of the Dye stuff Manufacturing Industry (ETAD), aims were established to minimize environmental damage, protect users and consumers and to cooperate fully with Govt. and public concerns over the toxicological impact of their products. Over 90% of some 4000 dyes tested in an ETAD survey had LD50 values greater than 2x103 mg /kg. The highest rates of toxicity were found amongst basic and diazo direct dyes. Government legislation is becoming more and more stringent, especially in the more developed countries; regarding the removal of dyes from industrial effluents. Environment Policy in UK, since September 1997 has stated that zero synthetic chemicals should be released into the marine environment. Enforcement of this law will continue to ensure that textile industries treat their dye containing effluent to the required standard. European Community (EC) regulations are also becoming more stringent.

Effect Of Dye On DNA And RNA Content

It is known in the case of bacterial population in the activated sludge that the growth rate at the logarithmic phase increases in the proportion to the cellular RNA content. So a similar relationship in between cell growth and RNA synthesis was predicted. The ratio indicated that the growth inhibition strongly depends on the rate of RNA synthesis. The content ratios of the nucleic acids (RNA/DNA); decreased with the increasing dye concentration. These dyes act more preferentially to lower protein synthesis that inhibits cell division. Due to the inhibitive action; cell shape varied, cells growing under ordinary conditions appeared as small rods and those in the presence of dyes, as filaments. Ogawa noted that dye inhibits DNA synthesis by stabilizing the double helix and by inhibiting the enzyme activities.

Effect On Blood And Haemopoetic System

Some dye intermediates like benzene produce changes in the various components of blood either after short exposure or on prolonged exposure. The effects seen are reduction in the numbers of the red blood cells and hemoglobin content of the blood-causing anaemia. The toxic effect may cause bone- marrow depression, epileptic anemia and hemorrhagic diseases of the various organs and leukemia in few cases.

Decolorization By Bacteria

Many organisms are reported to decolorize various triphenlymethane and azo dyes. There are a few reports on the biodegradation of theses dyes by bacteria. In 1981 Yatome reported the biodegradation of triphenylmethane dyes by Pseudomonas pseudomallei 13NA. In general the decolorization of the dyes is not related to their molecular weights and the octanol- water coefficients of the dyes. Yatome again reported the degradation of Crystal violet, Pararosaniline and Victoria growing cells of B.subtilis IFO13719.Biodegradation of triphenylmethane dyes by bacteria, fungi and yeasts.They showed the advantages of using biological processes for degradation of dyemolecules to carbon dioxide and water and with concomitant formation of less sludge andbeing eco-friendly.Decolorization of triphenylmethane dyes and textile and dyestuff effluent by Kurthia sp. They screened a number of soil and water samples and isolated the Kurthia species on the basis of rapid dye decolorization. Under aerobic conditions 98%of the color was removed intracellular by this strain. A number of dyes such as crystalviolet, malachite green. Ethyl violet etc was used for the studies. After the decolorization of most of the dyes, viable cell concentration of Kurthia sp. reduced significantly. Compared to crystal violet higher concentrations of malachite green was decolorized by the same amount of cell mass which may be due to the difference in the structure of boththe dyes.


1. To isolate bacteria from the soil which can degrade triphenylmethane dyes

2. To identify the gram nature of the isolated organism.

3. To identify the three isolated organism by using IMVIC test for each culture.

4. To estimate the percentage of decolorization of triphenlymethane dyes by microorganisms.

5. To find the enzyme activity on tri phenyl methane dyes.

6. To isolate DNA from the microorganisms which can decolorize triphenylmethane dyes.

7. To estimate DNA by di phenyl amine method.

8. To amplify TMR gene from chromosomal DNA isolated from dye degrading organism.


Pseudomonas strain from the textile dye effluent which could decolorize malachite green and crystal violet has been isolated. The activity of triphenylmethane dyes was estimated. The gene for triphenylmethane reductase was amplified. Pseudomonas aeruginosa is the bacterium which is used for the decolorization of the textile dyes malachite green and crystal violet.The activity of Triphenylmethane reductase enzyme responsible for decolorizing triphenylmethane dyes was observed. As the concentration of the dyes increases the activity of the enzyme decreases and as the concentration of the dye decreases, the enzyme activity increases. The gene for triphenylmethane reductase is isolated from the bacteria and that gene is amplified and is visualized on agarose gel.






<< back

Copyright © Dissertationideas.co.uk 2012 through 2014