Microbial Bioreactor Systems for Dehalogenation of Organic Pollutants

Microbial Bioreactor Systems for Dehalogenation of Organic Pollutants

Raghunath Satpathy (MITS Engineering College, India)
DOI: 10.4018/978-1-5225-3540-9.ch015
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Halogenated organic compounds having many beneficial applications, both in industries and agriculture sectors. Basically, the uses are as pesticides, solvents, surfactants, and plastics. However, their large, widespread uses throughout the world have resulted the negative impact on the environment. Considering their treatment process are widely accepted by using the bioreactor systems. The large variety of microorganisms present in the bioreactor and their interaction is the key to the effective treatment and removal of these compounds. Usually the microbes produce the enzymes known as dehalogenase to remove the halogen form the compounds to make it non-toxic. Many of the different steps and about the microbial groups in degradation process of halogenated compounds are well understood, but more details concerning the microbial community are yet to be discovered. This chapter describes about the different dehalogenation systems available in microbes and their ultimate application in different bioreactor systems for the degradation analysis of several harmful halogenated compounds.
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Halogenated organic compounds are the product from the industries and agriculture sectors and extensively used in many ways (Gribble, 1994; Song et al., 2000). Due to massive nature and continuous entry into the environment, the probability for the accumulation of these compounds in the habitats indicates a global threating. For example, some of these compounds like dichloro-diphenyl trichloroethane (DDT), polychlorinated biphenyl (PCB), dioxins and halogenated flame retardants have a destructive impact on human health also these are persistent in nature (Perocco et al., 1983; Muir et al., 2006; Rees et al., 2007). An important step in the degradation of harmful organohalide compounds is the cleavage of the carbon-halogen bond and the process is known as dehalogenation. This process is mediated by a diverse group of microorganisms (Schultz et al., 2001; Lin et al., 2011).The basis of microbial dehalogenation is the induction of an enzyme of dehalogenases that basically catalyzes the cleavage of carbon–halogen (C-X) bonds (Janssen et al., 1994; Chaudhry & Chapalamadugu 2001; Van Pee & Unversucht, 2003).Microbiological dehalogenation reactions have immense particular practical interests because of their potential biotechnological applications in the bioremediation of halogenated environmental pollutants (Fishbein, 1979). Many types of dehalogenase enzymes have been discovered in the microorganisms and that corresponds to the types of the halogenated pollutant to which the microorganism is exposed. The global halogen metabolism that occurs in the environment consists of both biotic and abiotic modes of halo-dehalogenation mechanism. For the last few years the number of natural organo-halogen compounds have been discovered more than 4000 today (Gribble, 2003; Velazquez et al., 2011). Examples of the halogenated hydrocarbons which are produced from biological sources are basically chlorinated phenols and phenolic ethers, halogenated terpenes, chlorinated amino acids and peptides, halogenated alkaloids, bromo- and chloro- substituted pyrroles, chlorinated insole, halogenated thiophenes, chlorinated prostaglandins, and various antibiotics (Gribble, 2004). However the toxic effect exhibited by different organohalidic compounds and their capacity for bioaccumulation in the food chain, food web and the creation of environmental contamination is a greater concern now (Table 1). So the major efforts have been taken to degrade the halogenated substances by using the microorganisms that play a major role the major mediators for the re-cycling of these halogenated organic compounds. Therefore, it is essential to study and understand the diverse microbial effect on the biodegradation and biotransformation processes (Hardman, 1991).

Key Terms in this Chapter

Bioreactor: A bioreactor is defined as a vessel system (may be flask, roller bottle, tank, or other container) used for bioprocessing that supports the growth of cells by formulating the medium and optimizing the conditions.

Chemical Oxygen Demand (COD): It is measure of the amount of oxygen that can oxidize the soluble and particulate organic matter in water.

Organic Pollutants: Organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes.

Bioremediation: Bioremediation is a treatment process that uses naturally occurring organisms to convert environmentally hazardous substances into its less toxic or non-toxic form.

Dehalogenase: The dehalogenases are a group of enzymes produced especially in microbes that catalyzes the removal of a halogen atom from a halogenated substrate.

Microbial Consortia: A microbial consortium is the interaction (preferably symbiotic type) between two or more microbial groups in a given environment.

Toxic Substances: A toxic substance is a substance that can be lethal or cause health hazards when uptake by the body.

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