Phenol degradation anaerobic

Phenol is an important intermediate in the anaerobic degradation of many complex and simple aromatic compounds. Tschech and Fuchs proposed that the carboxylation of phenol to 4-hydroxybenzoate is the first step in the degradation of phenol under denitrifying conditions. However, 4-hydroxybenzoate is not detected in the cultures or cell extracts of the denitrifying Pseudomonas species in the presence of CO2 and phenol, but it is detected if phenol is replaced by phenolphosphate. In contrast, 4-hydroxybenzoate is readily detected as an intermediate of phenol degradation in the iron-reducing bacterium GS-15, and 4-hydroxybenzoate may prove to be a common intermediate in the anaerobic transformation. Thus, in anaerobic degradation of phenolic compounds, it has been postulated that carboxylation reactions may play important roles. 

Groundwater contaminated with various phenols degraded in a methanogenic aquifer. Similar results were obtained in the laboratory utilizing an anaerobic digester. Methane and carbon dioxide were reported as degradation products (Godsy et al, 1983). 

Bolafios, M. L. R., Varesche, M. B. A., Zaiat, M., Foresti, E. Phenol degradation in horizontal-flow anaerobic immobilized biomass (HAIB) reactor under mesophihc conditions. Water Sd Technol 2001,44,167-174. 

The anaerobic degradation of some hydroxybenzoates and phenols involves reductive removal of the phenolic hydroxyl group. The enzyme that dehydroxylates 4-hydroxybenzoyl-CoA in Thauera aromatica is a molybdenum-flavin-iron-sulfur protein (Breese and Fuchs 1998), and is similar to the enzyme from the nonsulfur phototroph Rhodopseudomonas palustris that carries out the same reaction (Gibson et al. 1997). 

Henriksen HV, S Larsen, BK Ahring (1991) Anaerobic degradation of PCP and phenol in fixed-film reactors the influence of an additional substrate. Water Sci Technol 24 431 36. 

The degradation of Cg-benzene was studied in anaerobic enrichment cultures when phenol, benzoate, and toluene were detected, and the kinetics of their formation studied (Ulrich et al. 2005). 

It has become clear that benzoate occupies a central position in the anaerobic degradation of both phenols and alkylated arenes such as toluene and xylenes, and that carboxylation, hydroxylation, and reductive dehydroxylation are important reactions for phenols that are discussed in Part 4 of this chapter. The simplest examples include alkylated benzenes, products from the carboxylation of napthalene and phenanthrene (Zhang and Young 1997), the decarboxylation of o-, m-, and p-phthalate under denitrifying conditions (Nozawa and Maruyama 1988), and the metabolism of phenols and anilines by carboxylation. Further illustrative examples include the following ... 

Knoll G, J. Winter (1989) Degradation of phenol via carboxylation to benzoate by a defined, obligate syn-trophic consortium of anaerobic bacteria. Appl. Microbiol. Biotechnol. 30 318-324. 

The anaerobic degradation of phenol proceeds by carboxylation of phenyl phosphate, followed by dehydroxylation, and fission of the ring after partial reduction (Brackmann and Fuchs 1993). 

Karlsson A, Ejlertsson J, Nezirevic D, Svensson BH (1999) Degradation of phenol under meso- and thermophillic, anaerobic conditions. Anaerobe 5(l) 25-35... 

Degradation to carbofuran phenol was most rapid under anaerobic conditions (Venkatswarlu and Sethunathan 1978). 

TCE is the other major contaminant at the site and is a common groundwater contaminant in aquifers throughout the United States [425]. Since TCE is a suspected carcinogen, the fate and transport of TCE in the environment and its microbial degradation have been extensively studied [25,63, 95,268,426,427]. Reductive dechlorination under anaerobic conditions and aerobic co-metabolic processes are the predominant pathways for TCE transformation. In aerobic co-metabolic processes, oxidation of TCE is catalyzed by the enzymes induced and expressed for the initial oxidation of the growth substrates [25, 63, 268, 426]. Several growth substrates such as methane, propane, butane, phenol, and toluene have been shown to induce oxygenase enzymes which co-metabolize TCE [428]. 

Available data indicate that phenol biodegrades in soil under both aerobic and anaerobic soil conditions. The half-life of phenol in soil is generally less than 5 days (Baker and Mayfield 1980 HSDB 1997), but acidic soils and some surface soils may have half-lives of between 20 and 25 days (HSDB 1997). Mineralization in an alkaline, para-brown soil under aerobic conditions was 45.5, 48, and 65% after 3, 7, and 70 days, respectively (Haider et al. 1974). Half-lives for degradation of low concentrations of phenol in two silt loam soils were 2.70 and 3.51 hours (Scott et al. 1983). Plants have been shown to be capable of metabolizing phenol readily (Cataldo et al. 1987). 

While degradation is slower under anaerobic conditions, evidence presented in the literature suggests that phenol can be rapidly and virtually completely degraded in soil under both aerobic and anaerobic conditions (HSDB 1997). 

Ehrlich GG, Goelitz DF, Godsy EM, et al. 1982. Degradation of phenolic contaminants in ground water by anaerobic bacteria St. Louis Park, MN. Ground Water 20 703-710. 

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