Open Library - открытая библиотека учебной информации

Открытая библиотека для школьников и студентов. Лекции, конспекты и учебные материалы по всем научным направлениям.

Биотехнологии Theme and problems of ecological biotechnology, its significance in a modern society
просмотров - 120

Lecture 1

The surroundings around us are termed as ‘environment’. Our environment includes the abiotic component (the non living) and biotic component (the living). The abiotic environment includes air, water and soil; and the biotic environment consists of all living organisms such as plants, animals and microorganisms. Environmental pollution broadly refers to the presence of undesirable substances in the environment which are harmful to man and other organisms. There has been a significant increase in the levels of harmful environmental pollution mostly due to direct or indirect human activities in recent past. The major sources of environmental pollution are industries, agricultural and other anthropogenic and biogenic sources etc. The pollutants are chemical, biological and physical in nature. Controlling the environmental pollution and the conservation of environment and biodiversity and controlling environmental pollution are the major focus areas of all the countries around the world. In this context, the importance and impact of biotechnological approaches and the implications of biotechnology has to be thoroughly evaluated. There have been serious concerns regarding the use of biotechnological products and the impact assessment of these products due to their interaction with the environmental factors. A lobby of the environmentalists has expressed alarm on the release of genetically engineered organisms in the atmosphere and have stressed on thorough investigation and proper risk assessment of these organisms before releasing them in to the environment. The effect of the effluents from biotechnological companies is also a cause of concern for everyone. The need of the hour is to have a proper debate on the safety of the use of the biotechnological products. The efforts are not only on to use biotechnology to protect the environment from pollution but also to use it to conserve the natural resources. As we all know that microorganisms are known natural scavengers so the microbial preparations (both natural as well as genetically engineered) can be used to clean up the environmental hazards.

Biotechnology is being used to provide alternative cleaner technologies which help to further reduce the hazardous environmental implications of the traditional technologies. Some fermentation technologies have some serious environmental implications. Various biotechnological processes have been devised in which all nutrients introduced for fermentation are retained in the final product, which ensures high conversion efficiency and low environmental impact.

In paper industry, the pulp bleaching technologies are being replaced by more environmentally friendly technologies involving biotechnology. The pulp processing helps to remove the lignin without damaging valuable cellulosic fibres but the available techniques suffer from the disadvantages of high costs, high energy use and corrosion. A lignin degrading and modifying enzyme (LDM) was isolated from Phanerochaete chrysosporum and was used, which on one hand, helped to reduce the energy costs and corrosion and on the other hand increased the life of the system. This approach helped in reducing the environmental hazards associated with bleach plant effluents.

In plastic industry, the conventional technologies use oil based raw materials to extract ethylene and propylene which are converted to alkene oxides and then polymerized to form plastics such as polypropylene and polyethylene. There is always the risk of these raw materials escaping into the atmosphere thereby causing pollution. Using biotechnology, more safer raw materials like sugars (glucose) are being used which are enzymatically or through the direct use of microbes converted into alkene oxides.e.g. Methylococcus capsulatus has been used for converting alkene into alkene oxides.

Bioremediation is defined as ‘the process of using microorganisms to remove the environmental pollutants where microbes serve as scavengers. The removal of organic wastes by microbes leads to environmental cleanup. The other names/terms used for bioremediation are bio-treatment, bio-reclamation, and bio-restoration. The term “Xenobiotics” (xenos means foreign) refers to the unnatural, foreign and synthetic chemicals such as pesticides, herbicides, refrigerants, solvents and other organic compounds. The microbial degradation of xenobiotics also helps in reducing the environmental pollution. Depending on the method followed to clean up the environment, the bioremediation is carried out in two ways:

In situ bioremediation – involves a direct approach for the microbial degradation of xenobiotics at the site of pollution which could be soil, water etc. The in situ bioremediation is generally used for clean up of oil spillages, beaches etc.;

Ex-situ bioremediation - In this the waste and the toxic material is collected from the polluted sites and the selected range of microorganisms carry out the bioremediation at designed place. This process is an improved method over the in situ bioremediation method.

Pseudomonas which is a soil microorganism effectively degrades xenobiotics. Different strains of Pseudomonas that are capable of detoxifying more than 100 organic compounds (e.g. phenols, biphenyls, organophosphates, naphthalene etc.) have been identified. Some other microbial strains are also known to have the capacity to degrade xenobiotics such as Mycobacterium, Alcaligenes, Norcardia etc.

In recent years, efforts have been made to create genetically engineered microorganisms to enhance bioremediation. This is done to overcome some of the limitations and problems in bioremediation. These problems are: a) Sometimes the growth of microorganisms gets inhibited or reduced by the xenobiotics. b) No single naturally occurring microorganisms has the capability of degrading all the xenobiotics present in the environmental pollution. c) The microbial degradation is a very slow process. d) Sometimes certain xenobiotics get adsorbed on to the particulate matter of soil and thus become unavailable for microbial degradation.

As the majority of genes responsible for the synthesis of enzymes with biodegradation capability that are located on the plasmids, the genetic manipulations of plasmids can lead to the creation of new strains of bacteria with different degradative pathways. Well known example of genetic manipulations of plasmids is development of ‘Superbug’, which is used for degrading a number of hydrocarbons of petroleum simultaneously such as camphor, octane, xylene, naphthalene etc.

We all know that, carbon dioxide (CO2) is the main cause of green house effect and rise in the atmospheric temperature. There is a steady increase in the CO2 content due to continuous addition of CO2 from various sources particularly from industrial processes. It is very clear that the reduction in atmospheric CO2 concentration assumes significance. Biotechnological methods have been used to reduce the atmospheric CO2 content at two levels:

Photosynthesis- Plants utilize CO2 during the photosynthesis which reduces the CO2 content in the atmosphere;

Biological Calcification - Certain deep sea organisms like corals, green and red algae store CO2 through a process of biological calcification. As the CaCO3 gets precipitated, more and more atmospheric CO2 can be utilized for its formation.

The sewage is treated to get rid of these undesirable substances by subjecting the organic matter to biodegradation by microorganisms. The biodegradation involves the degradation of organic matter to smaller molecules, such as CO2, NH3, PO4 etc., and requires constant supply of oxygen. The process of supplying oxygen is expensive, tedious, and requires a lot of expertise and manpower. These problems are overcome by growing micro-algae in the ponds and tanks where sewage treatment is carried out. The algae release the O2 while carrying out the photosynthesis which ensures a continuous supply of oxygen for biodegradation. The algae are also capable of adsorbing certain heavy toxic metals due to the negative charges on the algal cell surface which can take up the positively charged metals. The algal treatment of sewage also supports fish growth as algae are a good source of food for fishes.

The environmental impact assessment system requires proponents to foresee possible environmental impacts when a development project is being planned, and to conduct an environmental assessment. However, debate continues on exactly what kinds of environmental protection measures are needed and how they should be integrated into a given project to achieve desirable environmental results. Actions to deal with global warming and to prevent ozone layer depletion are gaining momentum, but currently available technologies may not be enough to meet the required targets. Technological advances are needed in order to make progress in solving these issues, as well as with the problem of dioxins. New developments are also needed in technologies for pollution removal and environmental restoration, in cases where environmental pollution has already been generated or is already accumulating in the environment.

Control questions:

  1. What is bioremediation? In what ways it is good for environmental clean up?
  1. What is ‘in situ bioremediation’?
  1. Write a short note on ‘ex situ bioremediation ‘with special reference to composting.
  1. How can the bioremediation of xenobiotics be done?