Microbial decolouration of azo dyes: a review.

The term bioremediation has been introduced to describe the process of using biological agents to remove toxic waste from environment. Bioremediation is the most effective management tool to manage the polluted environment and recover contaminated soil. Bioremediation is an attractive and successful cleaning technique for polluted environment. Bioremediation has been used at a number of sites worldwide, including Europe, with varying degrees of success. Bioremediation, both in situ and ex situ have also enjoyed strong scientific growth, in part due to the increased use of natural attenuation, since most natural attenuation is due to biodegradation. Bioremediation and natural attenuation are also seen as a solution for emerging contaminant problems, e.g. endocrine disrupters, landfill stabilization, mixed waste biotreatment and biological carbon sequestration. Microbes are very helpful to remediate the contaminated environment. Number of microbes including aerobes, anaerobes and fungi are involved in bioremediation process.

Review on Bioremediation of Polluted Environment: A Management Tool

Fungal decolouration and degradation of azo dyes: A review

Bioremediation is an inventive and optimistic technology which is applicable for the retrieval and reduction of heavy metals in water and polluted lands. Microorganism plays an essential part in bioremediation of heavy metals. By using genetic engineering, genetically modified organisms can be generated which can likely reduce different types of polycyclichydrocarbons (PAHs). Flavobacterium, Pseudomonas, Bacillus, Arthrobacter, Corynebacterium, Methosinus, Rhodococcus, Mycobacterium, Stereum hirsutum, Nocardia, Methanogens, Aspergilus niger, Pleurotus ostreatus, Rhizopus arrhizus, Azotobacter, Alcaligenes, Phormidium valderium, Ganoderma applantus are some microbial species that help in bioremediation of heavy metals. This review not only discussed about the importance of microbes for bioremediation of heavy metals but also discussed about the challenges and limitations of native and engineered bacteria for bioremediation. Significance of bioremediation with the help of genetically engineered bacteria is in light because of its eco-friendly nature and minimum health hazards other than the physio-chemical dependent strategies, which are less eco friendly and dangerous to life.

Bioremediation of heavy metals by microbial process

ioremediation is a remediation technology using biological systems to cope pollution problems. “Bioremediation is an ecologically sound and state-of-the-art technique that employs contaminants”(Dr. Barware All). “Bioremediation is the process of using bacteria and other biological enhancements under controlled conditions to control pollution caused by different components of gasoline and fuel oxygenates in the contaminated land and groundwater”(David Laughlin and Randy Mueller).

Bioremediation을 활용한 수질정화

Petroleum sludge is a complex mixture containing different quantities of waste oil, waste water, sand, and mineral matter. Petroleum industries are responsible for the generation of large quantities of sludge, which is a major source of environmental pollution. Oily sludges are hazardous wastes according to Environment Protection Act and Hazardous Wastes Handling Rules. These sludges cannot be disposed off as landfill, even if they are de-oiled unless they are totally remediated. Sludges generated by petroleum industries accumulate in crude oil tanks, refinery products tanks, desalters, and elsewhere during oil production and processing. The sludges containing recoverable oil less than 40% are considered as low oil content sludges. These sludges have to be treated and made harmless before disposal. Bioremediation process can be used for this purpose. Generally, the refinery sludges contain oil content more than 40% and several methods are used to separate the oil, water and solids. The recovered oil is pumped back into the refinery process, while the solids and water are supposed to be treated before disposal. Several methods are available for processing and disposing of slop oil such as thermal, mechanical, biological, and chemical. Each method of processing has its advantages and disadvantages, and it is a common practice to utilize a combination of the four methods to maximize the output of usable oil from sludge. The first step in the process of disposing of the sludge is reclamation. In order to extract as much oil from the sludge as possible, a combination of chemicals and deemulsifiers is used. Topmost layers of oil are collected by the use of pumps and barges. The separation of the sludge is done with a centrifuge. The oil recovered is then delivered to a refinery or sold in the market. Hard particles, from which oil cannot be recovered, must then be disposed of. Hard particles are disposed of by the following ways: Incinerating unusable sludge (hard hydrocarbons-based substances mixed with water and emulsions) and harnessing heat and gases. Dehydration of sludge – the cleaned water is returned to the environment, and the hard particles are buried. Use of consolidating solutions for turning the sludge into a solid state. The solids can then be used in building projects. Use of Sludge as heat source. Biological remediation. The use of surfactants and emulsifiers will break up the old sludge and allow it to be removed from the container. Rhamnolipids, as a natural surfactant are useful in extracting these oil sludges and recovering them for use. These recovered sludges containing the rhamnolipid surfactants have most of the main properties of the original oil except for less viscosity.

Petroleum sludge, its treatment and disposal : a review

It is known that only 0.1 - 10% of all microorganisms observed in nature can be cultured under conventional laboratory conditions. This leaves researchers unable to study more than 99% of microorganisms in some environments - microorganisms that sometimes have unique and potentially very useful abilities such as waste degradation or synthesis of compounds that could find use as drugs or antibiotics. Metagenomics, the genomic reconstruction of unculturable microorganisms, is a powerful new tool for accessing the untapped resources of biodiversity in environmental samples. The ability to extract and purify high MW DNA from difficult samples such as waste effluents and soil, attempts to provide a breakthrough in representative metagenomic library construction for metagenomics that may enable the discovery of many future drugs and antibiotics.

	 

	Key words: Metagenomics, microorganisms, waste effluents and soil, drugs and antibiotics.

Metagenomics - An advanced approach for non- cultivable micro-organisms

Mercury resistant Escherichia coli strains have been isolated from different mercury polluted sites of India and their minimum inhibitory concentration (MIC) levels were determined. The zone of inhibition was measured to find the antibiotic sensitivity level. The location of mer operon was determined by transforming the isolated plasmids into mercury sensitive host DH5a cells. Plasmid isolated from transformed DH5a cells were also analyzed and compared with the plasmid profile of the wild-type strains. Oligonucleotides primer were designed by comparing the known reported sequences of merA from gram-negative bacteria (Escherichia coli R100) and 1695 bp of merA gene was amplified by PCR.

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Isolation, identification and PCR amplification of merA gene from highly mercury polluted Yamuna river

Sites contaminated by heavy metals and other pollutants are common through out the world. Researchers developed bioremediation as one feasible way to accelerate or encourage the degradation of pollutants from such affected sites. The basis of bioremediation is that all organisms remove substances from the environment to carry out their growth and metabolism. Bioremediation is not effective only for the degradation of pollutants but it can also be used to clean unwanted substances from air, soil, water and raw materials form industrial waste. With this in view, though many engineered processes for applying bioremediation have been developed but the inexpensive treatment of such sites has remained an elusive goal. Unlike organic contaminants, which often can be metabolized inexpensively into harmless substances such as carbon dioxide and water, metals and their salts that typically inhibit rather than support biological processes. However, in recent years there has been a flurry of interest developed in the implementation of biological approaches for bioremediation of at least some forms of inorganic contamination and paved the way for some other promising technologies to emerge.

	 

	Key words: Bioremediation, growth and metabolism, pollutants, environment.

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Bioremediation: A tool for environmental cleaning

Catechols are the most abundant organic pollutants of our environment. They are of major concern because of their persistence and toxicity and gave scientists a thinking to engineer/develop certain measures for its removal from the environment. Bacteria explore the environment for its nutritional requirement and degrade many of complex molecules available to them including the toxins and pollutants. Under biological process being the cheapest mode for removal of the catechols, the Pseudomonas putida has been found having the great potential to degrade them upto 500 mg/L. Such degradative bacteria, under normal circumstances, enzymatically convert xenobiotic, aromatic compounds to either catechol or protocatechuate. The most common catabolic pathway involves conversion of the parent molecules to chlorocatechols by the action of a monooxygenase or a dioxygenase. Many members of Pseudomonas carry plasmid that encodes enzymes capable of degrading aromatic and halogenated organic compounds. The degradation proceeds in two phases, first, an aromatic compound is prepared for ring cleavage by a variety of ring modification reactions. The second phase of degradation includes ring fission and subsequent reactions leading to the generation of tricarboxylic acid cycle intermediates. Two key enzymes involved in this 6-ketoadipate pathway are catechol 1, 2- dioxygenase and 3, 4-PCD.

Badrul Islam

Papers

Petroleum sludge, its treatment and disposal : a review

Metagenomics - An advanced approach for non- cultivable micro-organisms

Isolation, identification and PCR amplification of merA gene from highly mercury polluted Yamuna river

Bioremediation: A tool for environmental cleaning

Catechol biodegradation by pseudomonas strain : a critical analysis