Abstract
The demand and development of chemicals, pesticides, fertilizers, and pharmaceuticals is increasing constantly posing a potential threat to the environment. The presence of pesticides and their impact makes their removal and detoxification a more urgent need. Bioremediation technologies have been successfully used and are gaining more and more importance with increased acceptance of eco-friendly remediation solutions among the scientific community. Bioremediation by fungi and bacteria is considered a better option for making environment free from pesticides, as chemical and physical methods are not only costly but also not very effective. However, the complex nature of pesticides is an obstacle to degrade the pesticides, so more versatile and robust microorganisms need to be identified which can produce the desired result in a very cost-effective manner. This study examines the role played by fungi and bacteria in degradation of the pesticides in environment and also identify the future research problems in this regard that need to be experimented.
TopIntroduction
Rapid industrialization, urbanization and population growth has deteriorated the environment condition and is considered a threat for different kinds of ecosystems in many ways. Currently, land, water, air resources have become contaminated due to various toxic organo pollutants, viz., herbicides, insecticides, pesticides, plasticizers, coloring dyes, agrochemicals, solvents, pharmaceuticals, hydraulics, heavy metals, fire extinguishers, halogenated compounds, hazardous metal ions, etc. Human health and agricultural sustainability is seriously affected by the synthetic pesticides produced during the last 10 decades. The process of solidification and evaporation has exposed the environmental ecosystems to different types of pesticides and most of the pesticides are present in concentrations that are toxic to not only humans but to soil, water, marine and estuarine ecology. Pesticides traces have been found even in the samples of rain, fog and bark of trees as well.
Among the most persistent and globally distributed organic pollutants are hexachlorocyclohexane (HCH) and dichlorodiphenyltrichloroethane (DDT), hexachlorobenzene (HCB), heptachlor, aldrin, chlordane, dieldrin, endrin and mirex. Most of the organic compounds are synthetic and recalcitrant to photolytic, chemical, and biological degradation and due to their volatile nature these pesticides move long distances that results their distribution across the earth, including remote and isolated areas such as the Polar Regions (Allen-Gil et al., 1997). The pesticides can be transported in the vapour phase, surface runoff and leaching. The process of evaporation takes place due to tropical warm temperature and hence it is argued that trace of pesticides may be found in the atmosphere in areas where the temperature is high as compared to colder places. The concentration of pesticides will be highest near the point of release and decline with distance. However, mobile organo chlorine compounds that have their tendency to partition for easy movement are the exceptions (James, 2000). HCH isomers, DDT and its metabolites that are persistent organic compounds are the predominant chemical contaminants found along the Indian coast and were reported in major rivers (Rajendran & Subramanian, 1997; Zhou, Zhu, Yang, & Chen, 2006; Leong, Tan, & Mustafa, 2007; Imo, Sheikh, Hirosawa, Oomori, & Tamaki, 2007; Ma, Ran, Gong, & Zou, 2007; Ize-Iyamu, Asia, & Egwakhide, 2007; Kannel, Lee, Kanel, Khan, & Lee, 2007; Poolpak, Pokethitiyook, Kruatrachue, Arjarasirikoon, & Thanwaniwat, 2008; Doong, Lee, Lee, Sun, & Wu, 2008; Kaushik, Sharma, Jain, Dawra, & Kaushik, 2008). Organochlorine pesticide (OCPs) residues are important potential component of chemical pollutants used extensively for agriculture and sanitation purposes in India. These Pesticides enter the soil and ground water by direct treatment or being washed off from plant surfaces during rainfall. Depending on the phenotype and density of the plant type, it is estimated that an average of 35-50% of the plant protection material is deposited on soil immediately after spraying. The behavior of pesticides in soil and ground water involves persistence, movement and metabolism. The water solubility and binding capacity of organic and in organic constituents is an important factor for function of residues.
Key Terms in this Chapter
Leaching: Is the movement of contaminants, such as water-soluble pesticides or fertilizers, carried by water downward through permeable soils. Generally speaking, most pesticides adsorb to soil particles (especially clay), become immobile, and do not leach.
Xenobiotic: A xenobiotic is a foreign chemical substance found within an organism that is not normally naturally produced by or expected to be present within that organism. It can also cover substances which are present in much higher concentrations than are usual.
Biosparging: Is an i n-situ remediation technology that uses indigenous microorganisms to biodegrade organic constituents in the saturated zone. In biosparging, air (or oxygen) and nutrients (if needed) are injected into the saturated zone to increase the biological activity of the indigenous microorganisms.
Bioremediation: Bioremediation or bioaugmentation is the process of using naturally occurring microbes to digest and convert unwanted waste material into harmless substances. Our bioremediation products use friendly bacteria to digest and covert FOG into carbon dioxide and water.
Pesticide: A pesticide is any substance used to kill, repel, or control certain forms of plant or animal life that are considered to be pests.
Operon: In genetics, an operon is a functioning unit of genomic DNA containing a cluster of genes under the control of a single promoter.
Depolymerization: Is the process of converting a polymer into a monomer or a mixture of monomers. All polymers depolymerize at high temperatures, a process driven by an increase in entropy.
Cometabolism: It occurs when an organism is using one compound for growth and gratuitously oxidizes a second compound that is resistant to being utilized as a nutrient and energy source by the primary organism, but the oxidation products are available for use by other microbial populations.