SECTION 1
Enzymatic Processing of textiles.
Enzymes for cotton textile processing.
Properties of Various Enzymes

SECTION 2
New Trends in Enzymatic Processing
Use of Enzymes in Textile Effluent Treatment.

Enzymes in treating Textile Effluents:

ENZYMATIC DECOLORIZATION

In textile dyeing as well as other industrial applications, large amounts of dyestuffs are used. As a characteristic of the textile processing industry, a wide range of structurally diverse dyes can be used in a single factory, and therefore effluents from the industry are extremely variable in composition. This underlines the need for a largely unspecific process for treating textile waster water. It is known that 90% of reactive dyes entering activated sludge sewage treatment plants will through unchanged and be discharged in to rivers.

High COD and BOD, suspended solids and intense colour due to the extensive use of dyes characterize wastewater from textile industry, especially process houses. This type of water must be treated before discharging it into the environment. The water must be decolorized; harmful chemicals must be converted into harmless chemicals.

Biological treatments have been used to reduce the COD of textile effluents. Physical and chemical treatments are effective for colour removal but use more energy and chemicals than biological processes. They also concentrate the pollution into solid or liquid side streams that require additional treatments or disposal, on the contrary biological processes completely mineralize pollutants and are cheaper. Instead of using the chemical treatments, various biological methods can be used to treat the water from the textile industry. These methods include, Biosorption, use of Enzymes, Aerobic and anaerobic treatments etc. Only biotechnological solutions can offer complete destruction of the dyestuff, with a co-reduction in BOD and COD. In addition, the biotechnological approach makes efficient use of the limited development space available in many traditional dye house sites.

Decolorization of dyes by using biotechnology

The synthetic dyes are designed in such a way that they become resistant to microbial degradation under the aerobic conditions. Also the water solubility and the high molecular weight inhibit the permeation through biological cell membranes. Anaerobic processes convert the organic contaminants principally occupy less space; treat wastes containing up to 30,000 mg/l of COD, have lower running costs and produce less sludge. Azo dyes are susceptible to anaerobic biodegradation but reduction of azo compounds can result in odor problems. Biological systems, such as biofilters and bioscrubbers, are now available for the removal of odor and other volatile compounds.

The dyes can be removed by biosorption on apple pomace and wheat straw. The experimental results showed that 1 gm of apple pomace and 1 gm of wheat straw, with a particle size of 600 m, where suitable adsorbents for the removal of dyes from effluents. Apple pomace had a greater capacity to adsorb the reactive dyes taken for the study compared to wheat straw.

Decolorization of the dye house effluent using enzymes

The use of lignin degrading white-rot fungi has attracted increasing scienrific attention as these organisms are able to degrade a wide range of recalcitrant organic compounds such as polycyclic aromatic hydrocarbons, chlorophenol, and various azo, heterocyclic and polymeric dyes. The major enzymes associated with the lignin degradation are laccase, lignin peroxidase, and manganese peroxidase. The lacasses are the multicopper enzymes which catalyzes the oxidation of phenolic and non-phenolic compounds. However, the substrate of the laccases can be extended by using mediators such as 2,2-azoinobis-(3-ethylthiazoline-6-sulfonate)m 1-hydroxy benzotriazole. The following fungi have been used for laccase production and for the decolorization of synthetic dyes. Trametes modesta, trametes versicolor, trametes Hirsuta, and Sclerotium Rolfsii

From the results obtained it was clear that Trametes Modesta laccase showed the highest potential to transform the textile dyes into colorless products. The rate of the laccase catalyzed decolorization of the dyes increase with the increase in temperature up to certain degree above which the dye decolorization decreases or does not take place at all. The optimum pH for laccase-catalyzed decolorization depends on the type of the dye used. Dyes with different structures were decolorized at different rates. From these results it can be concluded that the structure of the dye as well as the enzymes play major role in the decolorization of dyes and it is evident that the laccase of trametes modesta, may be used for decolorization of textile dyestuffs, effluent treatments, and bioremediation or as a bleaching agent.

Activated sludge systems can also be used to treat the dye house effluents. But the main difficulty with activated sludge systems is the lack of true contact time between the bacteria of the system and the suspended and dissolved waste present. Immobilized microbe bioreactors (IMBRs) address the need of increased microbial/waste contact, without concomitant production of excessive biosolids, through the use of solid but porous matrix to which a tailored microbial consortium of organisms has been attached. This allowed greater number of organisms to be available for waste degradation without the need of a suspended population and greater increased contact between the organisms and the waste in question.