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PROJECT TOPIC AND MATERIAL ON ISOLATION, CHARACTERIZATION AND DECOLOURIZATION OF SYNTHETIC TEXTILES DYES BY THERMOPHILICHALOPHILICACTINOMYCETES SPECIES
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Anthropogenic influence of water resource is a global problem. The major pollutants such as dye stuffsfrom the textile industries affect the aquatic ecosystem. Due its toxicity it increases the Biological Oxygen Demand(BOD) and also depletes the oxygen in water. The conventional methods such as extraction, steam distillation,absorption, filtration etc., will have drawbacks of incomplete removal of dye stuffs.Enzymes reduces their adverse impact on the environment thereby making enzymatic wastewater treatment an ecologically sustainable technique.Two hundred and forty isolates were isolated from the cow dung, compost, soils where the hides and skin of animals were burnt. Three isolates displayed clear zones of inhibition characteristic of Actinomycetes. The isolates were further characterized by examining their colony morphology, cover slip culture techniques, gram staining reaction and amylase activity. The α-amylase activity was determined on solid medium supplemented with starch. The detection α-amylase activity of the isolates was based on the formation of clear zones around the colonies when flooded with iodine. The decolourization abilities of the isolates were also determined. The isolates showed good absorption characteristics and degrading capacity on the dye Congo red and brilliant green. It showed that Actinomycetes are potential decolorizer of dye stuffs and are good biosorbent.
Environmental pollution is one of the serious issues of concern in developing countries such as Nigeria. This could be due to industrial activities. Industrialization being a welcomed development has its negative side effects.The major pollutants such as dye stuffs from the textile industries affect the aquatic ecosystem. Due to its toxicity it increases the Biological Oxygen Demand(BOD) and also depletes the oxygen in water. The effluent discharge lead to pollution of the ground water. (Bello et al.,2013). Textile effluents have been found to contain a higher amount of metals especially chromium,copper,lead and cadmium.The metals are used in the production of color pigments of textile dyes. The toxic effect of dye stuffs and other organic compounds as well as acidic and alkaline contaminants from industrial establishments are widely unacceptable due to increased awareness of environmental issue.
Textile industry is one of the oldest and largest industries of. Synthetic dyes are coloring agents mainly used in textile industries which generate a huge amount of wastewater in the process of dyeing. It is estimated that these industries discharge around 280,000 tons of dyes every year into the environment. Discharge of these colored effluents into rivers and lakes results in the reduction of dissolved oxygen concentration, thus creating anoxic condition and leading to the acute toxic effects on the flora and fauna of the ecosystem. Azo dyes constitute the largest and most versatile class of synthetic dyes used in the textile industry due to their ease in production and variety in color compared to natural dyes (Pandey et al., 2007).Organisms such as Actinomycetes have been shown to specifically degradeazo dyes.
A dye can generally be described as a colored substance with an affinity to the substrate to which it is applied. Two percent of dyes produced are discharged into aqueous effluents while ten percent is subsequently lost during textile coloration process. (Easton 1995). Apart from the toxicological properties of dyes, their color is one of the first signs of contamination in a waste water.
It is therefore of great necessity to isolate thermophilicActinomycetes from natural sources like cow dung, compost and soil when the hides and skins of cows were burnt to isolate, characterize thermophilichalophilicActinomycetes and their ability to degrade and absorb dyes.
Effluents released from the textile industry are usually discharged into water bodies half treated or untreated (Bello et al.,2009). These dyes and other allied chemicals contribute to a major pollution load of the receiving water bodies .The major constituents of effluent discharged by dye is the color. It is the contaminant to be recognized in waste water and the presence of its very small amount in waste water is highly visible and undesirable. Synthetic dyes are used alongside with other toxic metals and the discharge of their effluents could have a very hazardous effect on the environment
Actinomycetes belong to the phylum Actinobacteria, which represents one of the largest taxonomic units currently recognized within the Domain Bacteria (Ventura et al., 2007). They are commonly believed to have a role in the recycling of nutrient and some exists as aerobes and some are anaerobes and are rich source of secondary metabolites with diverse biological activity.
Actinomycetes are a group of prokaryotic organisms belonging to subdivision of the gram- positive bacteria phylum. The Actinomycetes (order Actinomycetales) are bacteria that tend to form branching filaments which in some families develop into mycelium. They are regarded as higher bacteria because of this mycelia character. These bacteria closely resemble fungi in overall morphology. They are distinguished from other bacteria by their morphology DNA rich in guanine plus cytosine and on the basis of nucleic acid sequencing and pairing studies. The soil Actinomycetes produce a volatile compound called geosmin, which literally translates to “earth smell”. This organic substance contributes to the typical odour one gets when rain falls on soil (Uzel et al., 2011). Actinomyctes may be aerobic or anaerobic, although the thermophilic forms are primarily aerobic.
Actinomycetes are grouped as mesophilic, thermophilic and psychrophilic. The majority of them are mesophilic, growing at temperatures ranging from 18oC to 40oC. A few are thermophilic, which means that they have an optimum temperature for growth at 55oC and above. These thermophilicActinomycetes exist in soil, compost heaps, heating hays. The group of Actinomycetes areThermoactinomyces, Streptomyces and Thermomonospora species(Gousterovac et al., 2014). Thermophiles are the most primitive organisms which are important biotechnologically for thermostability, less incubation time, early sporulation and immense industrial feasibility. Many mesophilicActinomycetes are active in compost in the initial stage of decomposition.
With respect to dye biosorption,microbial biomass(bacteria,fungi, microalgae.)outperformed macroscopic materials(sea weed, crab shell).Many bacteria, fungi and microalgae have been found to bind a variety of dye classes.Research has revealed that inactive/dead microbial biomass can passively bind metal ions through various physiochemical mechanisms.
The bacterial cell wall provides structural integrity to the cell,but differs from that of all other organisms due to the presence of peptidoglycan which is responsible for the rigidity of the bacterial cell wall and determines the cell shape.It is also relatively porous and considered as an impermeability barrier to small substrates. Gram-positive bacteria are comprised of a thick peptidoglycan layer.
The bacterial cell wall is the first component that comes in contact with the dyes/ions, where all solutes can be deposited on the surface or within the cell wall structure (Beveridge and Murray, 1976;Doyle et al., 1980). Since the mode of solute uptake by dead/inactive cells play vital roles in biosorption.
Several biosorbents displaying metal-binding peptides on the cell surface have been successfully engineered.Genetic engineering has the potential to improve microorganisms, where biological metal-sequestering systems will have a higher intrinsic capability as well as specificity and greater resistance to ambient conditions(Baeet al.,2000;Majare and Bulow, 2001). A review of literature relating to biosorption revealed that several microbial biomass have been cultivated and explored for their biosorption potential.The cost of producing biomass for the sole purpose of its transformation into biosorbents has been shown to be too expensive(Tsezos,2001). Furthermore,the continous supply of biomass cannot be assured, which will have a huge impact on its successful application in industrial biosorption applications.
Actinomycetes are filamentous, branching gram positive bacteria witha fungal type morphology which are potent source for the production of novel antibiotics accounts for more than 50% of the known antibiotics discovered till date and date important in the field of pharmaceutical industries as well as in agriculture. ThermophilicActinomycetes are one of the most widely widelydistributed group of gram positive , mainly aerobic filamentous bacteria present in compost, peat, hot spring etc. Actinobacteria are widely distributed in both terrestrial and aquatic ecosystems, mainly in oil, where they plant an essential role in recycling refractory biomaterials by decompositing complex mixtures of polymer in dead plants, animals and fungal materials.
They are also very important in soil biodegradation and humus formation as they recycle the nutrients associated with recalcitrant polymers such as chitin, keratin and lignocellulose, this produces several volatile substances like geosmin responsible or the characteristic wet earth odour and exhibit diverse physiological and metabolic properties for example the manufacture of extracellular enzymes (StachandBull 2005).Antibiotics are the best known products of Actinomycetesfor their virtual success against pathogenic Microorganisnms antibiotics can truly be referred as the ‘wonder drugs’ (Demian, 1999)
Actinomycetes are widely distributed in both terrestrial and aquatic ecosystems mainly in soil, where they play an essential role in recycling refractory biomaterials by decomposing complex mixtures of polymers in dead plants, animals and fungal materials. They are also important in soil biodegradation and humus formation as they recycle the nutrients associated with recalcitrant polymers such as chitin, keratin and lignocelluloses (Stach and Bull 2005).This produces several volatile substances like geosmin responsible for the characteristic wet earth odour and exhibit diverse physiological and metabolic properties, for example the manufacture of extracellular enzymes.
Actinomyces contribute to around 70% of the source of antibiotics and also produce numerous non-antibiotics bioactive metabolites, such as enzymes, enzyme inhibitors, immunological regulators, anti-oxidation reagents. They are very hardy with respect to their moisture nutritional requirement but cannot withstand lower moisture dampness (Chavan et al., 2013). Streptomyces is the largest genus of Actinobacteria and the type genus of the family Streptomyceace. Found predominantly in soil and decaying vegetation, mainly Streptomyces produce spores and are noted for their distinct earthly odor which results from production of a volatile metabolites, geosmin. Streptomyces are characterized by a complex secondary metabolism. Actinomyces are considered to be microbiological curiosities of no great economic importance, have become the subjects of intensive searches for sources of new, biologically active compounds. Actinomycetes are dominantly present in soil but also ubiquitous in the natural habitats which facilitates a new hope that diverse group of Actinomycetes can be isolated in search of novel metabolites. Marine environments were recently found to be one of the important sources for the isolation of new Actinomyctes with potentiality to produce chemically diverse compounds with a wide range of biological activities (Bredholt et al., 2008).
Habitat of Actinomycetes
Actinomycetes constitute a significant component of the microbial population in most soils. It has been estimated that counts of Actinomycetes over 1 million per gram are commonly obtained. Over twenty genera have been isolated from soil, 95% isolates belonged to Streptomyces. Environmental factors influence the type and population of Actinomycetes in soil. Most Actinomycetes isolates behave as neutrophiles in culture, with a growth range from pH 5.0 to 9.0 and an optimium pH around 7.0. The pH is a major environmental factor determining the distribution and activity of soil Actinomycetes. Neutrophiles occur in less number in acidic soils below pH 5.0, whereas acidophilic and acidoduricStreptomycetes are numerous in acidic soils. However, there are few reports of to 9.5 was isolated from soil near a salt lake. Most Actinomycetes behave as mesophiles in the laboratory, with optimum growth temperatures at temperature at 25 to 30o. Many mesophilicactinomycetes are active in compost (Chavan et al., 2013).
Actinomycetes, particularly Streptomyces play a major role in antagonistic interactions in soil. Rhizosphere Streptomyces have been known as agents for control of fungal root pathogens.Many antagonistic interactions other than antibiotics may occur between Streptomyces and fungi. Reduced incidence of root infection has been correlated with an increase in number of Streptomyces in the rhizosphere which inhibits the pathogen by production of antifungal antibiotics. Actinoplanes can act as biological control agents of plant diseases (Chavan et al., 2013). Many mesophilicActinomycetes are active in compost in the initial stages of decomposition. However, the capacity for self-heating during decomposition provides ideal conditions for obligate or facultative thermophilicActinomycetes. Some genera like Thermo-ActinomycetesandSaccharomonospora are strictly thermophilic. ThermophilicActinomycetes grow well on animal manure. They have been active in fermentation of pig faeces, straw and deodorization of pig faeces.
Actinomycetes were mentioned incidentally in early studies on the microbial community of marine habitats. The selective isolation procedures and reliable diagnostic tests were not used in such pioneering surveys. There is evidence that Actinomycetes usually form a small fraction of the bacterial flora in marine habitats and counts are low compared with those from terrestrial and freshwater sites. Some workers considered Actinomycetes to be part of an indigenous marine microflora , whereas others saw them primarily as wash-in components that merely survived in marine and littoral sediments as spores. This latter view is supported by the observation that the numbers of Actinomycetes in marine habitats decrease with increasing distance from land (Cross,1981).
Characteristics and nutrition of Actinomycetes
Actinomycetes are heterotrophic in nature. Most of them are strict saprophytes, while some from parasitic or mutualistic associations with plants and animals. Actinomycetes are commonly believed to have a role in the recycling of nutrients. They are aerobic and some like Actinomycetes are anaerobic. The species like Frankia require very specialized growth media and incubation conditions. Many Actinomycetes are growing on the common bacteriological media used in the laboratory such as nutrient agar, trypticase agar, blood agar, brain heart infusion agar and starch casein agar. Sporo-Actinomycetes require special media to allow differentiation and the development of characteristic spores and pigments (Chavan et al., 2013).
Some of these media are not available commercially and must be prepared in the laboratory using colloidal chitin, soil extract and decoctions of plant materials. Pale, shiny, hard colonies of Streptomyces species on nutrient agar can be transformed into bright yellow colonies with a powdery white aerial mycelium and spirals of arthrospores when the organism is subcultured on a more suitable growth medium, such as oatmeal or inorganic salts starch agar. Outgrowths from a spore or fragments of mycelium develop into hyphae that penetrate the agar (substrate mycelium) and hyphae that branch repeatedly and become cemented together on the surface of the agar to form a tough, leathery colony. The density and consistency of the colony is depending on the composition (Chavan et al., 2013)
Actinomycetes secrete amylases to the outside of the cells to carry out extracellular digestion. Amylase starch degrading amylolytic enzymes is of great importance in biotechnological applications such as food industry, fermentation and textile to paper industries (Pandey et al., 2000).Actinomycetes are one of the known cellulose producers (Arunachalam et al., 2010).Cellulases are a collection of hydrolytic enzymes which hydrolyze the glucosidic bonds of cellulose and related cello-disaccharide derivatives. Lipase is produced from a variety of Actinomyces , bacteria and fungi ( Kulkarni and Gadre, 2002). Lipases have broad applications in the detergent industries, foodstuff, oleochemical, diagnostic settings and also in industries of pharmaceutical fields(Schmid et al., 1998).
Obi and Odibo (1984) reported that the isolation of species of thermoActinomycetes producing thermostable beta –amylase and their nutritional requirement for enzymes production.
Amylase are enzymes that hydrolysis starch to reducing sugars such as maltose and glucose (Forgarty and Griffin, 1975). Amylases have been widely reported to occur in microorganism as well as plants and animals. α – amylase and β –amylase are the major divisions of amylase.
Actinomycetes are of enormous importance since they possess a capacity to produce and secrete a variety of extracellular hydrolytic enzymes. Amylases have been widely reported to occur in microorganisms as well as plants and animals. α –amylase and β -amylase are the major divisions of amylases. Actinomycetes have more ability to bear not only at high salt concentration but also at high pH than bacteria and fungi. The soil is the main hub for microbial population, especially the Actinomycetes. Actinomycetes constitute a formidable group of industrially important microorganisms that have been explored for the production of thermostable enzymes. -amylase is been derived from several fungi, yeast, bacteria and Actinomycetes. It is used in food, textile, baking, pharmaceutical and detergent industries. It is also used in starch processing industry to convert starch to high fructose (Pandey et al., 2000; Asgher et al., 2007).Several species of Actinomycetes such as Streptomyces limosus and Thermomonosporacurvata have been found to be potent source of α – amylase enzymes. Other microorganisms such as Bacillus coagulans, Bacillus licheniformis, and Bacillusamyloliquefaciens are great sources of α – amylase enzymes. Several fungi have been reported to synthesize amylase (Cherry et al., 2004). Starch digestion is mainly done through the enzymatic method. Degradation of starch is carried out mainly and commonly by the action of amylolytic enzyme of bacterial origin ( Sohail et al.,2005).microbial amylases are mostly used in industries due to their high enzyme activity and thermostability ( Burhan et al., 2003). Their thermostability can be increased by pH, temperature or substrates. Enzymes involved in hydrolyses of starch are categorized into the following four groups based on their mode of action: α- amylase,β – amylase, glucoamylase and disbranching enzymes. α – amylase (α – 1,4glucan, 4 glucanohydrolase, is an extracellular enzyme which randomly hydrolyses α – 1,4 glucosidic linkage situated anywhere in either amylase or amylopectin chains.
Petroleum hydrocarbons are widely used in our daily life as chemical compounds and fuel. Greater use of result, petroleum has become one of the most common contaminants of large soil surfaces and eventually is considered as a major environmental problem (Sanscartier et al., 2009). There are several ways in which hydrocarbons degraded in the environment. One mechanism through which they can be removed from the environment is bioremediation. One mechanism through which they can be removed from the environment is bioremediation. Bioremediation is the use of soil microbes to degrade pollutants to harmless substances. Many strains have the ability to solubilize lignin and degrade lignin- related compounds by producing cellulose and hemicelluloses degrading enzymes and extracellular peroxidase (Mason et al., 2001). In some contaminated sites Actinomycetes represent the dominant group among the degraders (Johnsen et al., 2002).Actinomycetes species have the capability to live in an oily environment. So we can apply these microorganisms in bioremediation to deduct oil pollutants. Around 23,000 bioactive secondary metabolites produced by microorganisms have been reported and over 10,000 of these compounds are produced by Actinomycetes. Several pharmaceutical companies used microbial natural products as one of the major source of novel drugs. Researchers have been going on to discover more novel molecules with potential therapeutic application especially from Actinomycetes. A wide range of antibiotics in the market are obtainedfrom Actinomycetes. They are capable to degrade a wide range of hydrocarbons, pesticides and aliphatic and aromatic and also have a property to perform microbial transformations of organic compounds which are of great commercial value. They are a promising tool used in bioconversion of agriculture and urban waste into chemically vital products. Their metabolic potential offers a strong area for research. For novel drug delivery, scientists still exploit the chemical and biological diversity from diverse Actinomycetes group to maximize the possibility of successful discovery of novel strain in cost effective manner (Mukesh,2014)
Unlike most organic compounds, dyes have colour because they absorb light in the visible spectrum, have at least one chromophore, have a conjugated system, that is a structure with alternating double and single bonds and exhibit resonance of electrons, which is a stabilizing force in organic compounds (Shyamalaet al., 2014).Dyes contain one or moreazo groups ( azo dyes ) include by far the largest family of organic dyes. Distinguished types of dyes are acid dyes for protein and polyamide substance such as nylon, wool and silk. Dispense dyes for polyesters and acetate and direct and reactive dyes for cellulosic materials such as cotton, rayon, linen and paper. Dyes are used in many industries such as textile, food and pharmaceutical industries.
Many dyes are poisonous and since many are water soluble they can be hard to remove from industrial waste water. If these dyes are not removed from wastewaters, this could lead to damage of ecosystem and become poisonous for humans and animals. To be able to remove unwanted dye surplus from wastewater, immobilized bacteria can be utilized (Chen et al.,2003) in addition to aesthetically displeasing, the release of colloid effluent in water bodies reduces the photosynthesis as it impedes penetration of light in water. Interaction between dyes and biosorbent depends on the nature of dye, specific surface properties of biomass and environmental condition. The binding mechanisms of dye to biosorbent vary from physical to chemical.
Azo dyes are synthetically made compounds containing a double bound nitrogen group and are the most commonly used dyes in industries. There are about 3000 different kinds of azo dyes and they have a wide variety of colors and shapes and are easy to use for industrial purposes. Unfortunately, many of them are known to be toxic and even carcinogenic (Chen et al., 2003).Azo dyes are often highly water soluble and are therefore hard to remove from waste water. Because of this it is important to investigate possible treatment methods to minimize the amount released into ecosystems. Since many azo dyes have similar chemical structures one could assume that the degrading effects would be somewhat similar for other types of azo dyes.
Reactive dyes have intricate chemical structures which form covalent bonds between the reactive groups of cellulose and agiled functional groups of dye molecules. Reactive dyes are the most common dyes because of many advantages such as operating at mild conditions, give bright colors and stable structures (Wang and Lewis, 2002; Xie et al., 2008). Reactive dyes are nitrogen containing heterocyclic rings carrying halogen substituents, therefore undergo nucleophilic substation reaction with the cellulose fiber. The heteroatom activates the system for nucleophilic attack due to its electronegativity. The attacking nucleophile can be either a cellulose anion or a hydroxyl ion. This conducts fixation on the fabric, after hydrolysis occurs on the reactive dye and it is also important for a dye molecule to have a high dye fabric covalent fixation value.
Effluent from the industries containing reactive dyes causes serious environment pollution because, the presence of dyes in water is highly visible and affects their transparency and aesthetic even if the concentration of the dyes is low (Haoet al., 2000). Reactive dyes cause respiratory and nasal symptoms; asthma rhinitis and dermatitis; allergic contact dermatitis, mutagenicity (Mathur et al., 2005)genotoxicity, carcinogenicity and terraogenicity. Enzymes were used for decades in the textile industry as detergents, recently extracellular enzymes tested for their ability to decolor and degrade dyes (Gianfreda and Rao, 2004). To degrade dyes in a waste water plant, the chromophore in the dyes ahouldbe oxidized and cleaved. Laccase and manganese peroxidase are quite effective in dye degradation. Laccase for various fungi such as Trametesversicolor, Trameteshirsute ,Pleurotusostreatus , and Phlebiatremellosa are found to be effective decolourizer for a wide variety of structurally different dye ( Kandelbauer et al., 2004). Manganese peroxide decolours reactive orange 16, Remazol Brilliant blue R, Drimaren blue, Acid black and Drimaren red ( Novonty et al., 2004).
Discharge of effluent into water bodies are serious environmental problem. Reactive dyes are azo based dyes and they are recalcitrant to degrade by conventional treatment method. The biological treatment is an effective and alternate method to decolourize and mineralize the dyes in effluent without leaving harmful by products. In biological treatment the microorganisms bisorb or degrade the dyes with the help of some enzymes such as Laccases, lignin peroxidase, manganese peroxidase. Both anaerobic and aerobic condition is required for complete degradation of reactive dyes.
Actinomycetes now are being recognized for their degradative capacity of highly recalcitrant compounds. Actinomycetes have also shown to specifically degrade hydrocarbons (McCarthy and Willams,1992), chlorinated solvents (Wackett et al., 1989) , explosives ( Pasti-Grisby et al., 1996), plasticizers (Klausmeier and Osman, 1976) and azodyes ( Zhou and Zimmermann,1993). The effectiveness of microbial decolourization depends on the adaptability and activity of the selected microorganisms. In this context, to develop a practical bioprocess for treatment of dye- containing waste water it is important to isolate indigenous microbial stains (Chen et al., 2003).
Biosorption can be defined as the property of certain biomolecules to bind and concentrate selected ions and other molecules from aqueous solutions. Biosorption with microorganisms, especially fungus as latent sorbent for removal of dyes from industrial effluents has gained considerable attention. Decolourizing of synthetic dyes and effluentdyes have been reported by using various fungi (Binupriyaet al., 2007). Bacteria and fungi have been used for decolourization of effluent containing dye. Trametesversicolormycelium adsorbs dye of 5-10% and Aspergillusnigeradsorb 10-25% (Miranda et al., 1996).
Won et al., (2005) observed Corynebacteriumglutamicum as a latent biosorbent of reactive red Aeromonassp, Pseudomonas luteola,Escherichia coli , Bacillus reactive dyes like reactive blue, reactive red, reactive violet and reactive yellow. Actinomycetes as absorbent for decolourization of effluent containing anthraquinone, phalocyanine and azo dyes. Industrial effluents, like textile wastewater containing dyes must be treated before their discharge into the environment. The color removal of textile wastewater is a major environmental concern (Thakur et al., 2012). Colour can be removed from wastewater by chemical and physical methods including absorption, coagulation- flocculation, oxidation and electrochemical methods. These methods are quite expensive, have operational problems and generate huge quantities of sludge.
Thus, there is a need to find alternative treatments that are effective in removing dyes from large volumes of effluents and are low in cost. Biotreatment offers a cheaper and environmentally friendlier alternative for colour removal in textile in effluent biotreatment (Olukanni et al., 2006).Strains of bacteria, fungi and algae can be used extensively in bioremediation of textile effluents. These microorganisms produce both constitutive and inducible enzymes to bioremediate chemical compounds present in waste waters (Gupta et al.,2011). Though majority of bioremediation studies have been concentrated upon bacterial cultures not much work has been done using Actinomycetes.
Numerous bacteria capable of dye decolourisation have been reported. Efforts to isolate bacterial cultures capable of degrading azo dye started in the 1970s with reports on Bacillus subtilis. (Horitsu et al., 1997) similar reports were also made on Bacillus cereus, Pseudomonas and Aeromonas described a bacterial consortium capable of mineralizing the sulfonatedazo dye mordant yellow. Pseudomonas luteola grown well in media containing low glucose concentration (0.125) and without N-source showed 95% colour removal within 5-6 days under static incubation process.
Biodecolourisation of lignin containing pulp and paper wastewater as measured by the decrease in colour absorption using two basidiomycetes fungi phanerochaetechrysosporium and Tinctoporiaspwas reported as early as 1980 since then Phanerochaetechrysosporium in particular has been the subject of intensive research related to the degradation of a wide seqennce of recalcitrant xenobiotic compounds including azo dyes. Later several works were done Phanerochatechrysosporium its capability and mechanism of decolourisation (Cripps et al., 1990). Streptomyces spp can often be obtained by spreading a soil dilution on an agar medium containing polymers such as casein and starch. A single isolate may have different carbon sources. (Haug et al., 1991) compared the efficiency of a soil Actinomycete culture, Streptomyces chromofesusto that of Phanerochatechrysopriumand reported that fungi performed better than the actinomycetes.
Azo dyes constitute the largest class of dyes used commercially (lee et al., 2000). There are more than 8,000 chemical products listed in the color index which are associated with the dyeing process, while over 100,000 commercially available dyes exist with over 700,000 metric tons of dyestuff annually produced. Various fungal strains are known to degrade a wide variety of recalcitrant compounds, such as Xenobiotics, lignin and dyestuffs, with their extracellular enzymes. Many studies have also demonstrated that many fungal strains are capable of degrading various types of synthetic dyes such as azo, triphenyl methane, polymeric, phthalocyanine and heterocyclic dyes. Some fungal strains produce three kinds of enzymes (Laccase, lignin peroxidase (LiP) and manganese peroxidase (MnP), whereas others produce only one or two of them (Ha et al., 2001).
Biodegradation of azo dyes is being considered as an environment friendly and cost effective option which also offers environmental control. Environmental pollution due to urbanization and rapid growth of industries has an adverse effect on human health and ecology. Azo dyes constitute the largest and most versatile class of synthetic dyes used in the textile,pharmaceutical, paper, food and cosmetic industry due their ease in production and variety in colour compared to natural dyes (Pandey et al., 2007). These dyes are produced from known carcinogens and mutagens like benzidene. Laccasse are involved in biodegradation of lignin which constitute the main non-carbohydrate component in wood and are among the most abundant group of biopolymers in the biosphere. A great number of white –rot fungi have been reported to produce the lignin- degrading enzymes laccase, lignin peroxidase and manganes peroxidase or atleast one of these enzymes(Dey et al., 1994)
Azo dyes are the largest class of synthetic dyes due to the ease and cost effectiveness of their synthesis and the highest range of colours. Congo red is a diazo dye with a structure 3,3 – ((biphenyl)-4,4’diylbis(azo))-bis(4-amino-1-naphthalenesulphonic acid) disodium salt.(C32H22N6Na2O6S2). The UV-visible absorption spectrum shows intense around thepeak 498nm with molar mass of 696.668gmol-1. it is intended primarily for the colouration of paper products, used in medicine ( as a biological stain) and as an indicator since it turns from red-brown in basic medium to blue in acidic, used to colour textile and wood pulp. It is recalcitrant and acts as potent carcinogen and mutagenic because of presence of aromatic amine group. Azo dyes have long been recognized as a human urinary bladder carcinogen and Tumoringenic in animals cyanogenic in fishes, reduction in seed germination and induce dwarfism in plants. Due to more excessive use of Congo red in various industries possess a high threat to the environment. Varieties of microorganisms including bacteria, fungi, yeasts actinomycetes and algae are capable of degrading azo dyes, among which bacterial cells represent an inexpensive and promising tool for the removal of various azo dyes from textile dye effluents (Perumal et al., 2012). The mode of degradation of azo dyes is by production of azoreductase enzyme which cleaves azo bond and converts azo compounds to colourlessamines and functional groups.
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