Read this article to learn about the meaning, objectives, applications and different areas of environmental biotechnology.
Meaning of Environmental Biotechnology:
Environmental biotechnology in particular is the application of processes for the protection and restoration of the quality of the environment.
Environmental biotechnology can be used to detect, prevent and remediate the emission of pollutants into the environment in a number of ways.
Solid, liquid and gaseous wastes can be modified, either by recycling to make new products, or by purifying so that the end product is less harmful to the environment. Replacing chemical materials and processes with biological technologies can reduce environmental damage.
In this way environmental biotechnology can make a significant contribution to sustainable development. Environmental Biotechnology is one of today’s fastest growing and most practically useful scientific fields. Research into the genetics, biochemistry and physiology of exploitable microorganisms is rapidly being translated into commercially available technologies for reversing and preventing further deterioration of the earth’s environment.
Objectives of Environmental Biotechnology (According to Agenda 21):
The aim of environmental biotechnology is to prevent, arrest and reverse environmental degradation through the appropriate use of biotechnology in combination with other technologies, while supporting safety procedures as a primary component of the programme.
Specific Objectives are:
1. To adopt production processes that make optimal use of natural resources, by recycling biomass, recovering energy and minimizing waste generation.
2. To promote the use of biotechnological techniques with emphasis on bioremediation of land and water, waste treatment, soil conservation, reforestation, afforestation and land rehabilitation.
3. To apply biotechnological processes and their products to protect environmental integrity with a view to long-term ecological security.
Use of biotechnology to treat pollution problems is not a new idea. Communities have depended on complex populations of naturally occurring microbes for sewage treatment for over a century. Every living organism—animals, plants, bacteria and so forth—ingests nutrients to live and produces a waste as a by-product. Different organisms need different types of nutrients.
Certain bacteria thrive on the chemical components of waste products. Some microorganisms feed on materials toxic to others. Research related environmental biotechnology is vital in developing effective solutions for mitigating, preventing and reversing environmental damage with the help of these living forms. Growing concern about public health and the deteriorating quality of the environment has prompted the development of a range of new, rapid analytical devices for the detection of hazardous compounds in air, water and land. Recombinant DNA technology has provided the possibilities for the prevention of pollution and holds a promise for a further development of bioremediation.
Applications of Environmental Biotechnology:
Environmental protection is an integral component of sustainable development. The environment is threatened every day by the activities of man. With the continued increase in the use of chemicals, energy and non-renewable resources by an expanding global population, associated environmental problems are also increasing. Despite escalating efforts to prevent waste accumulation and to promote recycling, the amount of environmental damage caused by over-consumption, the quantities of waste generated and the degree of unsustainable land use appear likely to continue growing.
The remedy can be achieved, to some extent, by the application of environmental biotechnology techniques, which use living organisms in hazardous waste treatment and pollution control. Environmental biotechnology includes a broad range of applications such as bioremediation, prevention, detection and monitoring, genetic engineering for sustainable development and better quality of living.
Bioremediation:
Bioremediation refers to the productive use of microorganisms to remove or detoxify pollutants, usually as contaminants of soils, water or sediments that otherwise intimidate human health. Bio treatment, bio reclamation and bio restoration are the other terminologies for bioremediation. Bioremediation is not a new practice. Microorganisms have been used for many years to remove organic matter and toxic chemicals from domestic and manufacturing waste discharge.
However, the focus in environmental biotechnology for fighting different pollution is on bioremediation. The vast majority of bioremediation applications use naturally occurring microorganisms to identify and filter toxic waste before it is introduced into the environment or to clean up existing pollution problems.
Some more advanced systems using genetically modified microorganisms are being tested in waste treatment and pollution control to remove difficult-to-degrade materials. Bioremediation can be performed in situ or in specialized reactors (ex situ). Bioremediation by microorganisms need appropriate environment for the clean up of the polluted site.
Addition of nutrients, terminal electron acceptors (O2/NO2), temperature, moisture to promote the growth of a particular organism may be required for the microbial activity in the polluted site. Bioremediation operations may be made either on-site or off-site, in situ or ex situ. Bioremediation has a vast potential to clean up water and soil contaminated by a variety of hazardous pollutants, domestic wastes, radioactive wastes etc.
Biological cleaning procedures make use of the fact that most organic chemicals are subjected to enzymatic attack of living organisms. The most common approach is the use of enzymes as substitute chemical catalysts. Significant reduction or complete elimination of harsh chemicals may be achieved as is observed in leather, textile processing and pulp and paper industry.
Only 1-2g of hemicellulose is substituted for 10-15 kg of chlorine to treat 1 tonne of pulp, thereby significantly reducing the chlorinated organic effluent. Environmental protection and remediation presently combine biotechnological, chemical, physical and engineering methods.
The relative importance of biotechnology is increasing as scientific knowledge and methods improve. Its lower requirements for energy and chemicals, combined with lower production of minor wastes, make it an increasingly desirable alternative to more traditional chemical and physical methods of remediation. Applications of bioremediation for maintenance of environment are several. In this chapter a few are dealt with as handling of waste water and industrial effluents, soil and land treatment, air and waste gases management.
Waste Water and Industrial Effluents:
Water pollution is a serious problem in many countries of the world. Rapid industrialisation and urbanization have generated large quantities of waste water that resulted in deterioration of surface water resources and ground water reserves. Biological, organic and inorganic pollutants contaminate the water bodies.
In many cases, these sources have been rendered unsafe for human consumption as well as for other activities such as irrigation and industrial needs. This illustrates that degraded water quality can, in effect, contribute to water scarcity as it limits its availability for both human use and the ecosystem. Treatment of the waste water before disposal is of urgent concern worldwide.
In sewage treatment plants microorganisms are used to remove the more common pollutants from waste water before it is discharged into rivers or the sea. Increasing industrial and agricultural pollution has led to a greater need for processes that remove specific pollutants such as nitrogen and phosphorus compounds, heavy metals and chlorinated compounds.
Methods include aerobic, anaerobic and physico-chemical processes in fixed-bed filters and in bioreactors in which the materials and microbes are held in suspension. Sewage and other waste waters would, if left untreated, undergo self-purification but the process requires long exposure periods. To speed up this process bioremediation measures are used.
However, Five Key Stages are Recognized in Wastewater Treatment:
a) Preliminary treatment – grit, heavy metals and floating debris are removed.
b) Primary treatment – suspended matters are removed.
c) Secondary treatment – bio-oxidize organic materials by activities of aerobic and anaerobic microorganisms.
d) Tertiary treatment – specific pollutants are removed (ammonia and phosphate).
e) Sludge treatment – solids are removed (final stage).
Aerobic Biological Treatment:
Trickling filters, rotating biological contactors or contact beds, usually consist of an inert material (rocks/ash/ wood/ metal) on which the microorganisms grow in the form of a complex biofilm. These have been used for more than 70 years for sewage and waste water treatment. In these processes the degradable organic matter is oxidized by the microorganisms to CO2 that can be vented to the atmosphere.
Activated Sludge Process:
This process is used for treatment and removal of dissolved and biodegradable wastes, such as organic chemicals, petroleum refining wastes textile wastes and municipal sewage. The microorganisms in activated sludge generally are composed of 70-90% organic and 10-30% inorganic matters.
The microorganisms found in this sludge are usually bacteria, fungi, protozoa and rotifers. Petroleum hydrocarbons are degraded by species of bacteria (Acinetobacter, Mycobacteria, Pseudomonas etc.), yeasts, Cladosporium and Scolecobasidium. Pesticides (aldrin, dieldrin, parathion, malathion) are detoxified by fungus Xylaria xylestrix. Pseudomonas (a predominant soil microrganism) can detoxify organic compounds like hydrocarbons, phenols, organophosphates, polychlorinated biphenyls and polycyclic aromatics.
Utilisation of immobilized cyanobacterium Phormidium laminosum in batch and continuous flow bioreactors for the removal of nitrate, nitrite and phosphate from water has been reported by Garbisu et al. (2003). Blanco et al. (2003) showed the biosorption of heavy metal by Phormidium laminosum immobilised in micro-porous polymeric matrices. Photo-bioreactors are currently used to grow algae and cyanobacteria under closely controlled environmental conditions, with a view to making high-value products (such as beta-carotene and gamma-linoleic acid), designing efficient effluent treatment processes, and providing new energy sources.
The costs of wastewater treatment can be reduced by the conversion of wastes into useful products. Sulphur metabolizing bacteria can remove heavy metals and sulphur compounds from waste streams of the galvanization industry and reused. Most anaerobic wastewater treatment systems produce useful biogas.
In some cases, the by-products of the pollution-fighting microorganisms are themselves useful. Methane, for example, can be derived from a form of bacteria that degrades sulphur liquor, a waste product of paper manufacturing.
Soil and Land Treatment:
As the human population grows, its demand for food from crops increases, making soil conservation crucial. Deforestation, over-development, and pollution from man-made chemicals are just a few of the consequences of human activity and carelessness. The increasing amounts of fertilizers and other agricultural chemicals applied to soils and industrial and domestic waste-disposal practices, led to the increasing concern of soil pollution. Pollution in soil is caused by persistent toxic compounds, chemicals, salts, radioactive materials, or disease-causing agents, which have adverse effects on plant growth and animal health.
Many species of fungi can be used for soil bioremediation. Lipomyces sp. can degrade herbicide paraquat. Rhodotorula sp. can convert benzaldehyde to benzyl alcohol. Candida sp. degrades formaldehyde in the soil. Aspergillus niger and Chaetomium cupreum are used to degrade tannins (found in tannery effluents) in the soil thereby helping in plant growth.
Phanerochaete chrysosporium has been used in bioremediation of soils polluted with different chemical compounds, usually recalcitrant and regarded as environmental pollutants. Decrease of PCP (Pentachlorophenol) between 88-91% within six weeks was observed in presence of Phanerochaete chrysosporium.
Bioremediation of contaminated soil has been used as a safe, reliable, cost-effective and environment friendly method for degradation of various pollutants. This can be effected in a number of ways, either in situ or by mechanically removing the soil for treatment elsewhere.
In situ treatments include adding nutrient solutions, introducing microorganisms and ventilation. Ex situ treatment involves excavating the soil and treating it above ground, either as compost, in soil banks, or in specialised slurry bioreactors. Bioremediation of land is often cheaper than physical methods and its products are largely harmless.
During biological treatment soil microorganisms convert organic pollutants to CO2, water and biomass. Degradation can take place under aerobic as well as under anaerobic conditions. Soil bioremediation can also be accomplished with the help of bioreactors. Degradation can take place under aerobic as well as under anaerobic conditions. Soil bioremediation can also be accomplished with the help of bioreactors. Liquids, vapours, or solids in a slurry phase are treated in a reactor. Microbes can be of natural origin, cultivated or even genetically engineered.
Research in the field of environmental biotechnology has made it possible to treat soil contaminated with mineral oils. Solid-phase technologies are used for petroleum-contaminated soils that are excavated, placed in a containment system through which water and nutrients percolate. Biological degradation of oils has proved commercially viable both on large and small scales, in situ and ex situ.
In situ soil bioremediation involve the stimulation of indigenous microbial populations (e.g. by adding nutrients or aeration). In this process the environmental conditions for the biological degradation of organic pollutants are optimized as far as possible. Oxygen has to be supplied by artificial aeration or by adding electron acceptors such as nitrates or oxygen releasing compounds. Ozone dissolved in water and H2O2 are sometimes used which degrade the organic contaminants.
Air and Waste Gases:
With the onset of human civilization, the air is one of the first and most polluted components of the atmosphere. Most air pollution comes from one human activity: burning fossil fuels—natural gas, coal, and oil—to power industrial processes and motor vehicles. When fuels are incompletely burned, various chemicals called volatile organic chemicals (VOCs) also enter the air. Pollutants also come from other sources.
For instance, decomposing garbage in landfills and solid waste disposal sites emits methane gas, and many household products give off VOCs. Expanding industrial activities have added more contaminants in the air.
The concept of biological air treatment at first seemed impossible. With the development of biological waste gas purification technology using bioreactors—which includes bio filters, bio trickling filters, bio scrubbers and membrane bioreactors—this problem is taken care of. The mode of operation of all these reactors is similar.
Air containing volatile compounds is passed through the bioreactors, where the volatile compounds are transferred from the gas phase into the liquid phase. Microbial community (mixture of different bacteria, fungi and protozoa) grow in this liquid phase and remove the compounds acquired from the air.
In the bio filters, the air is passed through a bed packed with organic materials that supplies the necessary nutrients for the growth of the microorganisms. This medium is kept damp by maintaining the humidity of the incoming air. Biological off-gas treatment is generally based on the absorption of the VOC in the waste gases into the aqueous phase followed by direct oxidation by a wide range of voracious bacteria, which include Nocardia sp. and Xanthomonas sp.
Prevention:
Sustainable development and quality living depends upon the rational, eco-friendly use of natural resources with economic growth. To comply with this trend, industrial development has to change to sustainable style from degradative type and for such a purpose cleaner technologies have to be adopted.
According to United Nations Environment Programme (1996) ‘the continuous application of an integrated preventive environmental strategy to processes, products and services to increase eco-efficiency and reduce risks to humans and the environment’ defines the eco-friendly concept. The application of preventive and clean concept can only be achieved by the 5R policies (Olguin et al, 2003).
Five Environmental Buzzwords are the 5Rs for Efficient Use of Energy and Better Control of Waste, Which Might Help in Sustainable Development and Quality Living:
1. Reduce (Reduction of waste)
2. Reuse (Efficient use of water, energy)
3. Recycle (Recycling of wastes)
4. Replace (Replacement of toxic/hazardous raw materials for more environment- friendly inputs)
5. Recover (useful non-toxic fractions from wastes)
Innovation and adoption of clean technologies is the target of research and development worldwide. Industrial companies are developing processes with reduced environmental impact responding to the international call for the development of a sustainable society. There is a pervading trend towards less harmful products and processes; away from “end-of-pipe” treatment of waste streams. Environmental biotechnology, with its appropriate technologies, is suitable to contribute to this trend.
Enzyme Application:
Enzymes are widely employed in industries for many years. Enzymes, non-toxic and biodegradable, are biological catalysts that are highly competent and have numerous advantages over non-biological catalysts. The use of enzyme by man, both directly and indirectly, have been for thousands of years.
In the recent years enzymes have played important roles in the production of drugs, fine chemicals, amino acids, antibiotics and steroids. Industrial processes can be made eco-friendly by the use of enzymes. Enzyme application in the textile, leather, food, pulp and paper industries help in significant reduction or complete elimination of severe chemicals and are also more economic in energy and resource consumption.
Biotechnological methods can produce food materials with improved nutritional value, functional characteristics, shelf stability. Plant cells grown in fermenters can produce flavours such as vanilla, reducing the need for extracting the compounds from vanilla beans. Food processing has benefited from biotechnologically produced chymosin which is used in cheese manufacture; alpha-amylase, which is used in production of high-fructose corn syrup and dry beer; and lactase, which is added to milk to reduce the lactose content for persons with lactose intolerance.
Genetically engineered enzymes are easier to produce than enzymes isolated from original sources and are favoured over chemically synthesized substances because they do not create by-products or off-flavours in foods.
Environmental Detection and Monitoring:
A wide range of biological methods are in use to detect pollution and for the continuous monitoring of pollutants. The techniques of biotechnology have novel methods for diagnosing environmental problems and assessing normal environmental conditions so that human beings can be better- informed of the surroundings. Applications of these methods are cheaper, faster and also portable.
Rather than gathering soil samples and sending them to a laboratory for analysis, scientists can measure the level of contamination on site and know the results immediately. Biological detection methods using biosensors and immunoassays have been developed and are now in the market. Microbes are used in biosensors contamination of metals or pollutants. Saccharomyces cerevisiae (yeast) is used to detect cyanide in river water while Selenastrum capricornatum (green alga) is used for heavy metal detection. Immunoassays use labelled antibodies (complex proteins produced in biological response to specific agents) and enzymes to measure pollutant levels. If a pollutant is present, the antibody attaches itself to it making it detectable either through colour change, fluorescence or radioactivity.
Biosensors:
A biosensor is an analytical device that converts a biological response into an physical, chemical or electrical signal. The development of biosensors involves integration of a specific and sensitive biologically derived sensing elements (immobilized cells, enzymes or antibodies) are integrated with physico-chemical transducers (either electrochemical or optical). Immobilised on a substrate, their properties change in response to some environmental effect in a way that is electronically or optically detectable.
It is then possible to make quantitative measurements of pollutants with extreme precision or to very high sensitivities. The biological response of the biosensor is determined by the bio catalytic membrane, which accomplishes the conversion of reactant to product. Immobilised enzymes possess a number of advantageous features which makes them particularly applicable for use in such systems.
They may be re-used, which ensures that the same catalytic activity is present for a series of analyses. Biosensors are powerful tools, which rely on biochemical reactions to detect specific substances, which have brought benefits to a wide range of sectors, including the manufacturing, engineering, chemical, water, food and beverage industries. They are able to detect even small amounts of their particular target chemicals, quickly, easily and accurately.
For this character of biosensors they have been ardently adopted for a variety of process monitoring applications, principally in respect to pollution assessment and control. Biosensors for detection of carbohydrates, organic acids, glucosinolates, aromatic hydrocarbons, pesticides, pathogenic bacteria and others have already been developed.
The biosensors can be designed to be very selective, or sensitive to a broad range of compounds. For example, a wide range of herbicides can be detected in river water using algal-based biosensors; the stresses inflicted on the organisms being measured as changes in the optical properties of the plant’s chlorophyll. Biosensors are of different types such as calorimetric biosensors, immunosensors, optical biosensors, BOD biosensors, gas biosensors.
The remarkable ability of microbes to break down chemicals is proving useful, not only in pollution remediation but also in pollutant detection. A group of scientists at Los Alamos National Laboratory work with bacteria that degrade a class of organic chemicals called phenols. When the bacteria ingest phenolic compounds, the phenols attach to a receptor.
The phenol-receptor complex then binds to DNA, activating the genes involved in degrading phenol. The Los Alamos scientists added a reporter gene that, when triggered by a phenol-receptor complex, produces an easily detectable protein, thus indicating the presence of phenolic compounds in the environment. Biosensors employing acetylcholine esterase can be used for the detection of organophosphorus compounds in water.
Genetic Engineering:
Biotechnology, which is expected to make a great contribution to the welfare of mankind, is an important technology that should be steadily developed. The application of DNA technology, among the different kinds of biotechnology, has the possibility to create new gene combinations that have not previously existed in nature.
Since its beginning, genetic engineering has claimed to be able to construct tailor-made microorganisms with improved degrading capabilities for toxic substances. With the development of GEM (genetically engineered microorganism) and their possible utilization in the treatment of contaminated soil and water, stability of plasmids is extremely desirable. Plasmids are circular strands of DNA that replicates as separate entities independent of the host chromosome. Plasmids can range in size from those that carry only a couple of genes to ones carrying much greater numbers. Small plasmids may be present as multiple copies. Exchange of genetic information via plasmids is achieved by the process of conjugation.
The use of restriction enzymes has enabled the isolation of particular DNA fragments that can be transferred to another organism lacking the same. Genes which code for metabolism of environmental pollutants such as PCB’s and other xenobiotic compounds are frequently, although not always, located on plasmids.
The possibility of genetic transfer in non-biodegradative microbes has opened a new outlook of bio treatment of wastes. The recombinant DNA has the ability to multiply and may also confer the specific derivative capacity to detoxify environmental contaminants.
Gene transfer among microbial communities has improved the derivative capacity in vitro. The first patent for a genetically modified organism (GMO) or GEM, filed in the USA by Professor A. M. Chakrabarty was for a bacterium Pseudomonas putida with hydrocarbon degrading abilities. Subsequent reports have noted the role of plasmids in degradation of alkanes, naphthalene, toluene, m— and p— xylenes.
Given the overwhelming diversity of species, biomolecules and metabolic pathways on this planet, genetic engineering can, in principle, be a very powerful tool in creating environmentally friendlier alternatives for products and processes that presently pollute the environment or exhaust its non-renewable resources.
Nowadays organisms can be supplemented with additional genetic properties for the biodegradation of specific pollutants if naturally occurring organisms are not able to do that job properly or not quickly enough. By combining different metabolic abilities in the same microorganism blockage in environmental cleanup may be circumvented.
In the USA some genetically modified bacteria have been approved for bioremediation purposes but large scale applications have not yet been reported. In Europe only controlled field tests have been authorized. Just as light, heat, and moisture can degrade many materials, biotechnology relies on naturally occurring, living bacteria to perform a similar function but the action is faster.
Some bacteria naturally feed on chemicals and other wastes, including some hazardous materials. They consume those materials, digest them, and excrete harmless substances in their place. Bioremediation uses natural as well as recombinant microorganisms to break down toxic and hazardous substances already present in the environment. Bio treatment can be used to detoxify waste streams at the source before they contaminate the environment – rather than at the point of disposal. This approach involves carefully selecting organisms, known as biocatalysts, which are enzymes that degrade specific compounds and accelerate the degradation process.
However, the application of GMOs/GEMs, in the environment for bioremediation may create problems in the ecosystem. These exclusively designed organisms do not get a chance to experience the various fluctuating environmental conditions which is faced by naturally occurring organisms during the evolutionary processes spaning millions of years.
As a result, the latter are well adapted to the changing environmental conditions such as changes in temperature, substrate or waste concentrations. But when exposed to the contaminated site, GMOs show a higher viability than naturally occurring bacteria, due to their tailored enzymatic equipment.
There are concerns about the negative effect of these GMOs on the complex and delicate microbial ecosystems by competition or the exchange of genetic material in the soils to which they are applied. Even more worrisome is their potential effect outside the treatment area. While recombinant strains may appear harmless in the laboratory, it is virtually impossible to assess their impact in the field.
Biotechnical methods are now used to produce many proteins for pharmaceutical and other specialized purposes. Human insulin, the first genetically engineered product to be produced commercially (1982) is made by nonvirulent strain of Escherichia coli bacteria, by introduction of a copy of the gene for human insulin.
When the gene is “amplified” the bacterial cells produce large quantities of human insulin that are purified and used to treat diabetes in human beings. A number of other genetically engineered products have been approved since then, including human growth hormone, alpha interferon, recombinant erythropoietin and tissue plasminogen activator.
Biotechnology techniques are being applied to plants to produce plant materials with improved composition, functional characteristics. Among the first commercially available whole food products was the slow-ripening tomato, the gene for polygalacturonase, the enzyme responsible for softening, is turned off in this tomato. Plants that are resistant to disease, pests, environmental conditions, or selected herbicides or pesticides are also being developed.
In 1995, the Environmental Protection Agency (EPA) gave clearance for development of transgenic corn seed, cotton seed, and seed potatoes that contain the genetic material to resist certain insects. The advantage of such products is that they allow the use of less toxic and more environmentally friendly herbicides and pesticides.
The first approved application of biotechnology to animal production was the use of recombinant bovine somatotropin (BST) in dairy cows. Bovine somatotropin, a protein hormone found naturally in cows, is necessary for milk production. When the recombinant BST is administered to dairy cows under ideal management conditions, milk production has been shown to increase by 10% to 25%.
Other uses of biotechnology in animal production include development of vaccines to protect animals from disease, production of several calves from one embryo (cloning), artificial insemination, improvement of growth rate and/or feed efficiency, and rapid disease detection.
Natural bio-pesticides are another development of biotechnology that help farmers reduce chemical use. They degrade rapidly, leave no residues, and are toxic only to target insects. Bacillus thuringiensis (B.t.), produces a protein that is naturally toxic to certain insects. Scientists have extracted the B.t. gene that expresses the insecticide and inserted it into common bacteria that can be grown in large quantities by the same fermentation techniques used to produce such everyday products as beer and antibiotics. Spread on cotton and other crops, these harmless bacteria control insects naturally.
Moreover, a wide range of crop plants have been genetically engineered to express the cry genes (found in B. t.) in their tissues, so the insects get killed as they feed on these crops. Pollution control by genetic engineering is likely to work best when pollutants are a known mixture of relatively concentrated organic compounds that are related to each other in structure, where conventional alternative organic nutrients are absent, and when there is no competition from indigenous microorganisms.
The spectacular metabolic versatility of bacteria and fungi is exploited in the area environmental bioremediation as in sewage and waste water treatment, degradation of xenobiotics and metal abatement. Genetic manipulation offers a way of engineering microorganisms to deal with a pollutant, or a family of closely related pollutants, that may be present in the waste stream from an industrial process.
The simplest approach is to extend the degradative capabilities of existing metabolic pathways within an organism either by introducing additional enzymes from other organisms or by modifying the specificity or catalytic mechanisms of enzymes already present.
A treatment plant at the Homestake Mine in Lead, South Dakota, purifies 4 million gallons of cyanide-containing wastewater a day by completely converting cyanide to nitrate. Pseudomonas sp. convert cyanide and thiocyanate to ammonia and bicarbonate and the nitrifying bacteria Nitrosomonas and Nitrobacter cooperate in converting ammonia to nitrate. Recombinant DNA technology has had amazing repercussion in the last few years in environmental protection and also in other fields for better quality of living.
Different Areas of Environmental Biotechnology:
Environmental Biotechnology and Metagenomics:
Environmental Biotechnology is Divided into Different Areas:
(i) Direct studies of the environment,
(ii) Research with a focus on applications to the environment and
(iii) Research that applies information from the environment to other venues.
Here, a brief account of a particular aspect of direct analysis of environment is given.
In addition to DNA inside living organisms, there is much free DNA in the environment that might also be a source of new genes. The field of environmental biotechnology has revolutionized the study of the life-forms which have not been studied earlier and DNA.
This approach is direct analyses of the environment and the natural biochemical processes that are present. A significant study in this aspect is metagenomics. Metagenomics is the study of the genomes of whole communities of microscopic life forms and it deals with a mixture of DNA from multiple organisms, viruses, viroids, plasmids and free DNA.
In other words, metagenomics, the genomic analysis of a population of microorganisms, is the method to gain access to the physiology and genetics of uncultured organisms.
Using metagenomics, researchers investigate, catalogue the current microbial diversity. New proteins, enzymes and biochemical pathways are identified. The knowledge garnered from metagenomics has the potential to affect the ways we use the environment. Metagenomic analyses involves isolating DNA from an environmental sample, cloning the DNA into a suitable vector, transforming the clones into a host bacterium and screening the resultant transformants.
The clones can be screened for phylogenetic markers such as 16S rRNA and rec A or for other conserved genes by hybridization or multiplex PCR or for expression of specific traits such as enzyme activity or antibiotic production or they can be sequenced randomly.
One very important method for metagenomic study is stable isotope probing (SIP). An environmental sample of water or soil is first mixed with a precursor such as methanol, phenol, carbonate or ammonia that has been labeled with a stable isotope such as 15N, 13C or 18O. If the organisms in the sample metabolize the precursor substrate, the stable isotope is incorporated into their genome.
When the DNA from the sample is isolated and separated by centrifugation, the genomes that incorporated the labeled substrate will be heavier and can be separated from the other DNA in the sample. The heavier DNA will migrate further in a cesium chloride gradient during centrifugation. The DNA can be used directly or cloned into vectors to make a metagenomic library. This technique is useful to find new organisms that can degrade contaminants such as phenol.
Microorganisms are crucial participants in cleaning up a large variety of hazardous substances/chemicals by transforming them into forms that are harmless to people and environment. One very important example is given here. Gasoline is leaked into soil in every gas station in United States.
There is every possibility that gasoline will be mixed with ground water which is the prime source of drinking water. However, the dormant members of the soil microbial community are triggered to become active and degrade the harmful chemicals in gasoline.
Since gasoline is composed of hundreds of chemicals it takes a variety of microbes working together to degrade them all. When some bacteria cause a depletion of O2 in ground water near a gasoline spill, other types of bacteria that can use nitrate for energy begin biodegrading the gasoline. Bacteria that use iron, manganese and sulfate follow.
All these microbial communities work together in a pattern to transform leaking gasoline into CO2 and water. Metagenomic analysis may help us identify the particular community member and function needed to achieve the full chemical transformation that will keep our planet livable.