Authors Maithri S. Rai, P.Rama Bhat, P.S.Prajna, K.Jayadev and P.S.Venkatakrishna Rao
Colors gives delightful pleasure to eyesight but at the same time they may act as serious pollutants when their origin is dyes and dyestuffs. Textile industries have been using dyes intensively because of their ease and cost effectiveness in synthesis most widely used in textile, rubber, and enamel, plastic, cosmetic and many other industries, dyes are chemically diverse and divided into azo, anthraquinone, heterocyclic polymers and triphenylmethane dyes. Most of these are stable against light, temperature and biodegradation and have therefore accumulated in the environment as recalcitrant compounds. Conventional waste-water treatment is not efficient to remove recalcitrant dyestuffs from effluents. Approximately 10,000 different dyes and pigments are produced worldwide and used extensively in the dye and printing industries. It is estimated that about 10-14% of the total dye used in the dyeing process may be found in wastewater. These dyes are recalcitrant, and toxic. They resist microbial biodegradation and are therefore not easily degraded in wastewater treatment plant. Thus, treatment of dye is yet one of the challenging tasks in environment field. Currently available methods such as chemical oxidation, reverse osmosis, adsorption, etc., suffer from disadvantages such as high cost, regeneration problems and secondary pollutants/sludge generation. Recently, Researchers have been focusing their attention to enzymatic treatment . A major class of synthetic dyes includes the azo, anthraquinones and triphenylmethane dyes. Dyes are difficult to degrade biologically, so that degradation of dyes has received considerable attention. About 10-15% of all dyes are directly lost to wastewater in the dyeing process.1-2 Thus, the wastewater must be treated before releasing into the natural environment. The Food and Drug Administration nominated MG as a priority chemical for carcinogenicity testing by the National Toxicology Program 1993. MG and its reduced form, leucomalachite green, may persist in edible fish tissues for extended periods of time. Therefore, there are both environmental and human health concerns about bioaccumulation of MG and leucomalachite green in terrestrial and aquatic ecosystems, The popularity and widespread use of azo dyes is due to several factors. As a group, they are color-fast and encompass the entire visible spectrum, and many are easily synthesized from inexpensive and easily obtained starting materials. Also, azo dyes are typically amenable to structural modification, and can be made to bind to most synthetic and natural textile fibers. Because azo dyes are highly colored, they are readily apparent and can create a significant environmental problem by affecting water transparency as well as aesthetic problems, It is necessary to clarify the concepts of decolorization, degradation, and mineralization of dyes Decolorization is simply the disappearance of the color in wastewater without the actual breaking apart of the dye molecules, which does not necessarily mean degradation of the complex dye molecules. Degradation is the destruction of the large dye molecule to smaller components, along with the breakdown of the chromophores. While chromophore groups of dyes may be destroyed, the intermediate produced may be more toxic than the original compounds and could present significant problems for receiving water bodies. Mineralization means organic compounds are converted to inorganic compounds, i.e., nitrate, carbon dioxide, and water. In this case, a complete detoxification is achieved, and no secondary pollution will be introduced. Aloe gel also contains lignan, salicylic acid, saponins, sterols, and triterpenoids. The fresh gel contains the proteolytic enzyme carboxypeptidase (which breaks down bradykinin), glutathione peroxidase, as well as several isozymes of superoxide dismutase. The gel also contains vitamins A, C, E, B12, thiamine, niacin and folic acid, as well as the minerals sodium, potassium, calcium, magnesium, manganese, copper, zinc, chromium, and iron, (Aloe barbadensis and Aloe arborescens) chemical constituents, A. vera contains amino acids, lipids, sterols, tannins, enzymes flavonoids and mannose 6 phosphate, The percentage decolorization/ degradation was studied at different parameters like maximum part of plant showing degradation, effect of buffers, effect of pH, effect of temperature, effect of dye concentration, effect of enzyme quantity and effect of time period. Use of appropriate buffers, Congo red showed a maximum decoloration with skin extracts of Aloe vera and decoloration was up to 30% whereas Malachite green decoloration was maximum with pulp extract of Aloe barbadensis for each dye A buffer is needed for the activity of enzyme. Three buffers (Acetate buffer, phosphate buffer and citrate buffer) of Ph 7 were used. Effect of pH, pH factor was optimized to obtain maximum decoloration. pH ranges from 4-9, Effect of temperature, temperature plays an important role in the enzyme activity. Temperature range for30 C- 60 C,
