Halogenated phenols degradation

Since the aerobic degradation of halogenated phenols takes place by monooxygenation and is discussed in Part 2 of this chapter, it is not discussed here except to note the production of chlorocat-echols from chlorophenols and chloroanilines. Emphasis is placed on chlorinated substrates, and reference may be made to a review (Allard and Neilson 2003) for details of their brominated and iodinated analogs. The degradation of aromatic fluorinated compounds is discussed in Part 3 of this chapter. 

Miiller et al. 2004) (Figure 9.20). In contrast, halogenated phenols with three or more snbstitnents are degraded by pathways in which the halogen is removed by various reactions before ring hssion ... 

Haggblom, M. M. Young, L. Y. (1995). Anaerobic degradation of halogenated phenols by sulfate-reducing consortia. Applied and Environmental Microbiology, 61, 1546-50. 

Materials may exhibit a tainting odor from the polymers, monomers, additives, adhesives, or process. Packaging related taints, as reported from the Nestle s Central Packaging Laboratory over a 4-year period (1996-2000) were related to solvents (28%), degraded polyethylene (PE) (24%), styrene (15%), halogenated phenols (15%), degraded paper (3%),... 

Further details of the pathways for the degradation of PAFIs are described in Chapter 6, Section 6.2.1 and in a review (Neilson and Allard 1998). It seems that most of the degradative enzymes are inducible, and this is consistent with the fact that most strains have been isolated after specific enrichment with the xenobiotic. The case of the partially constitutive synthesis of catechol 1,2-dioxygenase in the yeast Trichosporon cutaneum (Shoda and Udaka 1980) has been noted (Section 4.5.2). In the case of biotransformation, however, there are sporadic examples of the constitutive synthesis of enzymes. For example, the system carrying out the O-methylation of halogenated phenolic compounds was apparently constitutive (Neilson et al. 1988) this observation is consistent with the isolation of the strains by enrichment with Q compounds structurally unrelated to the halogenated substrates. The O-methylation reaction may function primarily as a detoxification system, so that in this case constitutive synthesis of the enzyme would clearly be advantageous to the survival of the cells. 

A similar relationship was also found in the microbial degradation of various halogenated phenols (Alexander and Lustigman, 1966). Further investigation of such structural correlations may create good possibilities for the preparation of biodegradable pesticides of shorter life. 

Organic chemicals that are susceptible to oxidation and are of concern from the perspective of contamination and environmental degradation include aliphatic and aromatic hydrocarbons, alcohols, aldehydes, and ketones phenols, polyphenols, and hydroquinones sulfides (thiols) and sulfoxides nitriles, amines, and diamines nitrogen and sulfur heterocyclic compounds mono- and di-halogenated aliphatics linear alkybenzene-sulfonate and nonylphenol polyethoxylate surfactants and thiophosphate esters. Table... 

The photocatalytic degradation of chlorophenols on ZnO has also been demonstrated [127]. The photocatalytic degradation of other chlorinated aromatic compounds [127], phenol [128-134], fluorinated aromatic compounds [135], and other substituted phenols and aromatic compounds [Izumi 1981, 738 Matthews 1984, 2386 Abdullah 1990, 2099 [136-141] have been demonstrated. The degradation of halogenated aromatic pollutants such as polychlorinated biphenyls (PCBs) [142] and polybrominated dibenzofiirans [143] has also been attempted. 

The degradation of aromatics, pesticides, herbicides, and other bio-recalcitrant compounds in industrial wastewaters can be efficiently achieved by means of the oxidative radicals generated in the Fenton and photo-assisted Fenton reaction [11], Among others, the photo-Fenton method has proved to be effective in the degradation of phenol and its halogenated derivatives [12-14], dioxins [15], nitroaniline [16],... 

Batch reactors based on peroxidases are mainly applied for degradation purposes (see Chap. 8). LiP, manganese peroxidase (MnP), HRP, SBP, and CPO were used for the oxidation of phenolic compounds [3, 6, 7, 9, 20, 38, 74, 75, 95], decoloriza-tion of dye-containing effluents [5, 22], and pulp biobleaching [59]. In the field of synthesis, CPO is the most versatile and promising of the peroxidases (see Chap. 6). It was applied in discontinuous operation for epoxidations [78,79], enantioselective oxidations of alcohols to aldehydes [14,48], halogenations [77,80], hydroxylations, and oxidation of indole to oxindole, which is an important drug precursor [96]. 

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