ABSTRACT
Two hundred and forty isolates were isolated from the cow dung, compost, soils where the hides and skin of animals were burnt. Three isolates designated A1, A7, and A43 displayed clear zones of inhibition characteristic of Actinomycetes. The isolates were further characterized by examining their colony morphology, cover slip culture techniques, carbon utilization potentials, 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.
INTRODUCTION
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. All members of this order are characterized in part by high G + C content (>55mol%) in their DNA. The gram-positive bacteria fall into two major phylogenetic divisions, “low –GC” and “high –GC”. GC content is an abbreviation of GC base pairs in an organism DNA. Those that have a low GC content, have more AT base pairs in their DNA. 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 thermophilic Actinomycetes exist in soil, compost heaps, heating hays. The group of Actinomycetes are Thermoactinomyces, 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 mesophilic Actinomycetes are active in compost in the initial stage of decomposition. However, the capacity for self-heating during decomposition provides ideal conditions for obligate or facultative thermophilic Actinomyctes. Some genera like Thermo-actinomycetes and Saccharomonospora are strictly thermophilic. Thermophilic Actinomycetes grow well on animal manure. It was already shown that the Thermophilic Actinomycetes can produce amylases, Xylanases and cellulose digesting enzymes which retain their activity at high temperatures (50- 60oC).
They are characterized by a complex life cycle belonging to the phylum Actinobacteria, which represents one of the largest taxonomic units among the 18 major lineages currently recognized within the Domain Bacteria (Ventura et al., 2007). 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. Most of them are strict saprophytes, while some from parasitic or mutualistic associations with plants and animals. They are commonly believed to have a role in the recycling of nutrient and some exists as aerobes and some like are anaerobes and are rich source of secondary metabolites with diverse biological activity. Actinomycetes have more ability to bear not only high alt concentration but also at high pH than bacteria and fungi.
Textile industry is one of the oldest and largest industries of India. Synthetic dyes are colouring 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 worldwide every year into the environment. Discharge of these coloured 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, pharmaceutical, paper, food and cosmetic industry due to their ease in production and variety in colour compared to natural dyes (Pandey et al., 2007). Actinomycetes have been shown to specifically degrade hydrocarbons, chlorinated solvents, explosives, plasticizers and azo dyes.
It is therefore of great necessity to isolate thermophilic actinomycetes from natural sources like cow dung, compost and soil when the hides and skins of cows were burnt. The aim of this work is to isolate, characterize thermophilic halophilic actinomycetes and their ability to degrade and absorb dyes.
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