Bioremediation: Effective Approach towards a Cleaner Environment
By M.Faisal Siddiqui

Today millions of people are without basic needs of shelter, cloth, health, education and employment. It is not due to overpopulation alone but also due to environmental problems. Man obtains from the environment his life support systems and the basic components of environment air, water and soil, which contribute in various ways to fulfill the needs of human. The losses of forests, fertility of soil and energy crisis have created many problems.

These problems have created difficulties for human beings to maintain its existence, protection, survival and for the improvement of general standard. For centuries human believed that atmospheric, terrestrial and aquatic systems were sufficient to absorb and breakdown wastes from industries, farming and population centres.But now we know that this is not true. Today there are two fundamental problems: First, how we dispose of the large quantities of wastes that are continually being produced?Second,how we remove the toxic compounds that have been accumulating at dump sites, in soils, and in the water systems over the last few decades?.

Once again man has turned to modern tools of biotechnology for help. Controlling and improving the quality of environment has become a key area of biotechnological activity. Biotechnology ensures the safe disposal of these materials, but also enables their effective recycling as new source of energy of novel products.

The application of biotechnology has help in the environmental management of such hazardous contaminants by using different strategies which are collectively known as bioremediation. Bioremediation is the use of biological organisms such as bacteria, fungi, algae and plants to reduce or eliminate toxic pollutants from contaminated sites by degradation, assimilation or transpiration in the atmosphere. This process is also known as biotreatment or biorestoration.

The applicability of bioremediation can be considered for each of the environmental states of matter;(1)solids:soil,sediments,sludges.(2)liquids: ground water, industrial waste water.(3)gases: industrial air emissions, soil vent gas. Its applicability and success depends upon three factors: the properties of pollutants, the microbial community and the environment.

Bioremediation uses different approaches like; (1) intrinsic bioremediation: Monitor the natural biodegradation process. (2)Biostimulation: a process that increases activity of microbes to biodegrading contaminants. For example, addition of nutrients, oxygen or other electron donors and acceptors. (3)Bioaugumentation: The addition to the environment of microorganisms that can metabolize and grow on specific compounds. Selecting the most appropriate strategy to treat a specific site can be guided by considering three basic principles: the amenability of the pollutant to biological transformation to less toxic products (biochemistry), the accessibility of the contaminant to microorganisms (bioavailability) and the opportunity for optimization of biological activity (bioactivity).

The basic principle of bioremediation is the breakdown of organic contaminants into simple compounds like CO2, water, salts and other harmless products. The capacity could be improved by applying the genetically modified microbes and plants.

Microbial Bioremediation:

Bioremediation of organic contaminants is primarily based on either microorganism present naturally at the sites, or microbial inoculants developed in laboratory and introduced at site. Each microbe consumes very limited range of hydrocarbons or degrades pollutants at very slow rate. Therefore methods have been designed to use mixer of microbes along with inorganic nutrients such as phosphorous and nitrogen.

Use of Genetically engineered microbes:

Another option is to use genetically engineered microbes. Despite the ability of many naturally occurring microbes to degrade a number of different chemicals. There are limitations to the biological treatment of these waste materials. For example;(1)No single microorganism can degrade all organic wastes.(2)High concentrations of some organic compounds can inhibit the activity of microorganisms.(3)Often contaminated sites contain mixer of chemicals and a microbe which degrade one or more of the components of the mixer may be inhibited by other components.(4)Many compounds absorb onto particular matter into soil or sediments and become less available to degradative microorganisms and(5) and microbial biodegradation is often very slow.

In most cases a single plasmid (DNA) of bacteria carries the genes encoding the enzymes for a specific degradative pathway. By combining plasmid from different strains within a single host, it is possible to create an organism to create an organism with multiple degradative capabilities. In addition, by genetic manipulation the range of substrates degraded by a particular enzymatic pathway can be extended. In 1979,for the first time Anand Mohan Chakrabarty,an Indian born American scientist obtained a strain of Pseudomonas putida (bacterium) that contain the XYL and NAH plasmid as well as a hybrid plasmid .This strain could grew rapidly on crude oil because it was capable of metabolizing hydrocarbons more efficiently.

An American Microbiologist has discovered GS-15 microbe, which can eat up uranium from the waste water of nuclear weapon manufacturing plant. This microbe converts uranium in water into insoluble particles, can be collected and disposed off. It also metabolizes uranium directly.

Some Fungi can trap metallic ions in aqueous solutions. This is due to their special cell wall composition. Many fermented industries produces fungal biomass (unwanted by product), which can be used for this purpose. The biomass of fungus Rhizopus arrhizus can absorb 30-130 mg of cadmium/gm of dry biomass.

Algasorb a product patented by the biorecovery systems company absorbs any metal ion from the waste water or ground water.

Depolluting plants:

Aside from the world of microbes plants can play a better role in the removal of wastes from soil and ground water. This technology is known as phytoremediation,in which plants are used for degradation and removal of contaminants from soil and water.

For this purpose specially selected or engineered plants are used. Sites that have shallow, low level of contaminants are best candidates for phytoremediation.This technology can be used at polluted sites having pollutants such as metals,pesticides,solvents,explosives,radionuclides,crude oil etc.

Phytoremediation presents several ways in which can be used to clean up contaminated soil and water such as hytoextraction, phytotransformation, rhizospherebioremediation, phtostabilization and rhizofilteration.

Plants are selected and grown in contaminated areas for required growth period. They transform contaminants or absorb the pollutants through the root system and cumulate the water and nutrients essential for growth as well as other components. Then they are harvested and disposed off.

Different plants have been used in various applications like;

*poplar, willow, grasses, alfalfa are used for remediation of contaminants such as herbicides, nutrients and ammunition wastes.

*Mulbery, rye for pesticides.

*sunflower and barley for metals.

*aquatic plants such as duckweed, bulrush, for metals and radionuclides.

Genetic modification offers a new hope for phytoremediation;as GM approaches can be used to over express the enzymes involved in the existing plant metabolic pathways or to introduce new pathways into plants. A future biotechnological strategy for enhancing phytoremediation is enlarging root mass to increase adsorption area, using Agrobacterium rhizogenes to altered the root morphology.

The University of Arid Agricultural (UAA), Rawalpindi, has envisioned a research project. The man behind phytoremedaition project is Dr.A.G.Khan of University of Western Sydney,Australia.He is a PhD in soil microbiology from the University of Sydney and he has join the department of Botany, Faculty of Sciences of the UAA,as visiting professor under the higher education commission’s foreign hiring scheme.Dr.Khan is in the process of submitting two research project proposals for funding to HEC and the Pakistan science foundation in a new area like phytoremediation and also desires to establish a centre of excellence in this dimension of Biotechnology at the University of Arid Agriculture.

Bioremediation is an option that offers the possibility to destroy or render various contaminants using biological activity. Bioremediation uses relatively low cost, low technology techniques, which have a high public acceptance. It is a natural and safe process.Theoritically bioremediation is useful for the complete destruction of wide variety of contaminants. Many compounds that are larger can be transformed. It is non –disruptive and non-invasive. Bioremediation can often be carried out on site, often without causing of major disruption of normal activities .This eliminate the need to transport the quantities of wastes off sites and the potential threats to human health. Bioremediation is less expensive then other technologies that are used for cleanup of hazardous waste. It is easy to implement, environment friendly and does not require sophisticated or expensive equipments. Soil and ground water do not have to be removed and less waste or no waste to be dispose off. The complete restoration to basic constituents than simply transferring to another media (like atmosphere) People accept the idea that the technology utilizes naturally occurring microorganisms to degrade toxic compound into harmless products. The adverse reactions on the environment seem to be minimal.

Bioremediation is not without its faults. It is limited to those compounds that are biodegradable. Not all compounds are suspected to rapid and complete degradation. There are some concerns that the product of bioremediation may be more persistent or toxic than the parent compound. Biological processes are highly specific, important site factors are required for success include; the presence of metabolically capable microbial populations, suitable environmental growth conditions and appropriate levels of nutrients and contaminants.

Research is needed to develop and engineer bioremediation technologies that are appropriate for sites with complex mixer of contaminants that are not evenly dispersed in the environment. Bioremediation is very slow process than other traditional technologies(mechanical).Phytoremediation is dependent on the depth of root and tolerance of plants to contaminants.Exposur of animals to plants which acts as hyper accumulators, can also be a concern to environmentalists, as herbivorous animals may accumulate contaminated particles in their cells which could in turn effect a whole food web.Phytoremediation is also dependent on growing conditions(climate,altitude,temperature etc) required by the plant.

Controlling pollution at its source itself is an extremely effective approach towards a cleaner environment.A clean and healthy environment has strong appeal in all aspects of life. A great part of soil, water and air is already polluted and steps are being taken to cleanup these pollutants. The current challenges for bioremediation are to reduce or to eliminate pollutants added to the ecosystem. Bioremediation is an option that offers the possibility to destroy or render various contaminants using natural biological activity and it seems to be a good alternative to conventional cleanup technologies. Today every one has started thinking over the problem of environmental pollution and every effort should be made to focus public attention to save mankind from self-destruction and steps should be taken at national and international levels so that the consequences may not become worse.

M.Faisal Siddiqui
Editor Biotechnology Pakissan