Bioremediation of environmental pollutants: a novel approach
Authors: Vipin Kumar Gupta and Preeti Gupta
This article summarize the use of various biological organisms present in cow dung to destroy or reduce amount of pollutants in environment. Broad catalytic potential of microbes have a capability to attenuate or reduce the toxicity, volume, mass, concentration of contaminants in nature without human involvement. It is a better approach than conventional methods of remediation e.g. incineration, chemical decomposition etc., as basically, it is “bio” mediated decomposition of antimicrobials, pharmaceuticals, pesticides, biomedical waste, municipal waste or sludge with metal, petrochemical and other chemical industry waste, oil spillage or hydrocarbon fuel, motor oil, paper, paints, textile dyes, hydrocarbons and many more other contaminants and pollutants. It is a superior technique over using chemicals, as microorganisms are easy to handle and it is solely an eco-friendly method of remediation. Biodegradation and biotransformation are the initial process that results to bioremediation. It has at least three outcomes: first a minor alteration in a molecule leaving the main structure intact; second the fragmentation of a complex molecule to simpler form and third one complete mineralization, which is the degradation of organic structure to its mineral form. If any one of these processes is triggered or stimulated to get a cleaner and healthier environment then it is called as “bioremediation”.
The biological organisms associated in this process are aerobic bacteria, which degrade pesticides and hydrocarbons; alkanes and poly-aromatics. They may be able to use the contaminant as sole source of carbon and energy. Methanotrophs, aerobic bacteria that utilize methane for carbon and energy. Enzyme methane monooxygenase is active against a wide range of compounds e.g. chlorinated aliphatics such as trichloroethylene and 1, 2-dichloroethane. Anaerobic bacteria, this group are not frequently used. They can be utilized to degrade chloroform, trichloroethylene (TCE) and polychlorinated biphenyls (PCBs). Fungi, they are able to degrade a diverse range of persistent or toxic environmental pollutant and also have capability to bio-accumulate some heavy metal too.
How microbes use the contaminant: Contaminants may serve either as primary substrate; used as a sole energy and nutrient source or secondary substrate; imparts energy but not available in high enough amount or may act as co metabolic substrate; organism depends primarily on another substrate but this compound also utilized by it.
Enzymatic processes in bio remediation: Bio-degradation process uses microorganisms or their enzymes. Major types of enzymatic reactions are oxidation, decarboxylation, hydrolysis, substitution, elimination, reduction, dehalogenation, demethylation, deamination and condensation etc.
Different categories of environmental pollutants: These are divided mainly into three categories, first is bio-degradable, non-persistent; petroleum products like gas, diesel, fuel, crude oil, compounds like benzene, toluene, xylene, naphthalene, some pesticides like malathion, coal compounds like phenols, cyanide in coal tars and coal waste, some industrial solvents, etc., second is partially, slowly degradable, persistent; they remain for many year: TCE (trichlorethane), PCE (perchloroethane), PCB’s (polychlorinated biphenyls), arsenic, chromium, selenium etc., third category is non degradable / recalcitrant: uranium, mercury, lead etc.
Gomeya, an excellent bio-remediator for clean environment: Ayurveda stated that Gomeya or cow dung is a very useful product it purify all the wastes present in the nature (Ank K.G., 1995). It composed of a blend of dung and urine in a ratio of about 3:1. Basic constituents are crude protein, crude ﬁber, cellulose, hemi-cellulose, lignin and 24 minerals like nitrogen, potassium, sulphur, iron, magnesium, calcium, cobalt, manganese, and so forth (Nene Y. L., 1999). Microbial consortium of Gomeya contains about 60 species of bacteria, mainly comprised of Pseudomonas, Actinomycetes, Cellulomonas, Escherichia coli, Flavobacterium, Serratia, Nocardia, Sarcina, Salmonella, Staphyloccocus aureus, Alcaligens, Bacillus, Corynebacterium, Lactobacillus and Fecal streptococci etc., Fungi, Aspergillus and Trichoderma etc., around 100 species of Protozoa and Yeasts, Saccharomyces and Candida etc. Other constituents of cow dung comprised of undigested ﬁber, sloughed off intestinal epithelium, some excreted products derived from bile (pigments), intestinal bacteria and mucus. The bile pigment biliverdin is mainly present in cow dung (herbivore) giving it its green color. Bile salts give dung its emulsifying properties (Randhawa and Kullar, 2011).
Bioremediation of Antimicrobial Agents with cow dung: Medical prescriptions contains about 6% of antimicrobial agents, while in veterinary field, more than 70% of prescriptions contains them (Thiele-Bruhn S., 2003). Therefore, un-degraded antibiotics can leads to a thread and can develop multidrug resistant strains which indirectly affects public health, causing increased morbidity and mortality. Cow dung could serve as an applicable ecosystem model to study the fate of antibiotics. Some basidiomycetes were isolated from aged cattle dung. A strain identiﬁed as Cyathus stercoreus, showed high activity in the degradation of enroﬂoxacin (Wicklow D. T. et. al, 1980).
Bioremediation of Pesticides with cow dung: India is the largest producer of pesticides in Asia and ranks 12th in world for application of pesticides. 2%-3% of pesticide is actually utilized and the rest persists in environment causing pollution (WHO, 1990). The remediation of pesticide residue from soil and water is of prime importance to decontaminate the environment. Pseudomonas plecoglossicida is a reliable organism for bioremediation of toxicants like “cypermethrin” (Boricha and Fulekar, 2009) and “chlorpyrifos”, an organophosphate insecticide by Pseudomonas aeruginosa (Fulekar and Geetha, 2008).
Bioremediation of biomedical waste with cow dung: Present method of biomedical waste disposal is the use of incinerator which is not only costly but also not eco-friendly as it produces toxic gases like dioxins. Periconiella species of fungi derived from cow dung was found to be an effective degrader of biomedical waste (Pandey and Gundevia, 2008).
Bioremediation of municipal sludge with metal by cow dung: The impact of cow dung compost using earthworm E. foetida i.e. vermicompost, upon municipal sludge with heavy metals was studied in Lucknow, India. Earthworms are capable of bio-accumulating heavy metals in their body parts especially chloragocytes. All the metals including chromium, copper, nickel and lead were reduced after treatment (Srivastava et.al, 2005).
Bioremediation of petrochemical and other chemical industry waste by cow dung: This industry generate the waste such as phenol and benzene compounds. This approach will be useful to degrade them. Benzene is not biodegradable and is also carcinogenic. Remediation of benzene can be brought about by using cow dung microﬂora in a bioreactor. The Pseudomonas putida was isolated from cow dung microﬂora as a potential benzene degrader and its ability to degrade benzene at various concentrations (Singh and Fulekar, 2010). Phenol, the cow dung slurry containing bacteria, fungi and actinomycetes have successfully used in degrading phenol compounds (Singh and Fulekar, 2007). The organism Pseudomonas putida IFO 14671 has been isolated, identiﬁed and cultured from the cow dung microbial consortium as a high phenol degrader (Singh and Fulekar, 2009).
Bioremediation of oil spillage and motor oil with cow dung: When a solution of cow dung with water (1:10 – 1:25) is sprinkled over oil spillage in oceans, it has the capacity to soak the oil. Naturally occurring microflora in cow dung have the capability to degrade crude oil into simple and harmless compounds. Thus, it is a very useful method for controlling oceanic pollution and thus maintains the aquatic ecosystem. In a study, cow dung microﬂora was assessed for petroleum-utilizing bacteria. Pseudomonas and Bacillus were identiﬁed as petroleum utilizers in cow dung (Akinde and Obire, 2008). Motor oil, application of cow dung in appropriate concentration could be very useful in bioremediation of motor oil contaminated lagoon water (Umanu et al., 2013).
Composting or bio-augmentation is one of good example of bioremediation to tackle bio-degradable waste: It is carried out under controlled conditions in the presence of oxygen results in the biological decomposition and stabilization of the biodegradable components using cow dung. The process of composting includes four main phases; which are the initial phase, the thermophilic phase, the mesophilic phase and maturation phase after which the compost can be used as a soil tonic.
This approach is very effective, low cost and environmental friendly. This technology offers the possibility to destroy contaminants or render harmless using natural biological activity often by utilizing locally available constituents from the farms. Gomeya or cow dung will acts as an excellent bioremediation tool. It is not only effective for the degradation of pollutants but it can also be used to clean unwanted substances from air, soil, water and raw materials from waste or in other word it is a tool for prosperity as a whole.
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I am posted as Assistant Professor in the discipline Veterinary Public Health & Epidemiology
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