Phenols microbial degradation

During fermentation, the betacyanins turned out to be more stable than the betaxanthins, which is assumed to be due to their thermal stability rather than different tendencies of pigments toward microbial degradation. Besides these biological tools, beet extracts may also be purified by column chromatographic techniques. After removal of sugars, salts, and phenolics, the nature-derived color preparation will, however, require E number labeling. ... 

During decomposition of plant remains, many phenolic compounds are released by leaching, microbial degradation or are synthesized by microbial activity. In forestry, problems of natural regeneration and reforestation are connected to the presence of phenolic substances deposited in the soil. Methods for extrachon and identification of toxic substances from different soil types (mineral or organic) are described. The method for extracting of soil phytotoxins is based on the use of ethylacetate and methanol (free phenolics) and alkaline hydrolysis (bound phenolics). 

Shivaraman N, Kumaran P, Pandey RA, et al. 1985. Microbial degradation of thiocyanate, phenol and cyanide in a completely mixed aeration system. Environ Pollut, Ser A 39 141-150. 

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]. 

The behavior of phenolic compounds derived from decaying plant residues, or released from degrading humic substances, is dictated by the physico-chemical processes of adsorption and desorption. Equilibria between these processes determine the concentration of phenolic compounds in the soil solution and consequently the bioactivity, movement, and persistence of these substances in the soil. Surface interactions between phenolic compounds and colloidal matrices may promote their polymerization (25, 26) or protect them from microbial degradation and mineralization. 

Martin, J. R, and Haider, K. (1980). Microbial degradation and stabilization of 14C-labeled lignins, phenols, and phenolic polymers in relation to soil humus formation In Lignin Biodegradation Microbiology Chemistry and Potential Applications, Vol. II. Kent-Kirk, T., Higuchi, T., and Chang, H., eds., CRC Press, Boca Raton, FL, pp. 77-100. 

Although hydrolysis of the triazine herbicides is temperature and pH dependent, these herbicides are considered to be hydrolytically stable under the pH and temperature conditions encountered in natural waters. However, the relatively slow hydrolysis rates in natural waters may be enhanced somewhat by the presence of dissolved organic carbon (DOC) (in the form of fulvic acids and a variety of low-molecular-weight carboxylic acids and phenols) that has been shown to catalyze the hydrolysis of several triazine herbicides. Although microbial degradation is probably the most important mechanism of dissipation of the triazine herbicides in soils, abiotic hydrolysis of these herbicides also occurs. Hydrolysis in soils is affected by the pH, organic matter (humic acid) content, and the type and content of clay in the soil. 

Reversible sorption of phenolic acids by soils may provide some protection to phenolic acids from microbial degradation. In the absence of microbes, reversible sorption 35 days after addition of 0.5-3 mu mol/g of ferulic acid or p-coumaric acid was 8-14% in Cecil A(p) horizon and 31-38% in Cecil B-t horizon soil materials. The reversibly sorbed/solution ratios (r/s) for ferulic acid or p-coumaric acid ranged from 0.12 to 0.25 in A(p) and 0.65 to 0.85 in B-t horizon soil materials. When microbes were introduced, the r/s ratio for both the A(p) and B-t horizon soil materials increased over time up to 5 and 2, respectively, thereby indicating a more rapid utilization of solution phenolic acids over reversibly sorbed phenolic acids. The increase in r/s ratio and the overall microbial utilization of ferulic acid and/or p-coumaric acid were much more rapid in A(p) than in B-t horizon soil materials. Reversible sorption, however, provided protection of phenolic acids from microbial utilization for only very short periods of time. Differential soil fixation, microbial production of benzoic acids (e.g., vanillic acid and p-hydroxybenzoic acid) from cinnamic acids (e.g., ferulic acid and p-coumaric acid, respectively), and the subsequent differential utilization of cinnamic and benzoic acids by soil microbes indicated that these processes can substantially influence the magnitude and duration of the phytoxicity of individual phenolic acids (Blum, 1998). 

Microbial degradation of biocides has been described by Hugo [72] who points out that soil organisms are able to break down substances such as phenols added as fumigants. He also reviewed the utilization by bacteria of aromatic compounds (including the preservatives cresol, phenol, benzoic acid and esters of 4-hydroxybenzoic acid). Several types of preservatives and disinfectants, such as the QACs (e.g. cetrimide, cetylpyridinium chloride, benzalkonium chloride), chlorhexidine and phenylethanol can also be inactivated. Significantly, this only occurs at concentrations well below inhibitory or in-use concentrations [33] and thus cannot be responsible for insusceptibility. A further comment about chlorhexidine is given below. 

Eield, J. A. and Sierra-Alvarez, R. 2008. Microbial degradation of chlorinated phenols. Reviews in Environmental Science and Biotechnology, 7 211 1. 

Steiert, J.G. and R.L. Crawford. 1985. Microbial degradation of chlorinated phenols. Trends Biotechnol. 3 300-305. 

Coal tar constituents present in surface waters may be degraded by direct and indirect photolysis. Estimated aqueous photolysis half-lives of 8.4, 71, and 21 hours have been reported for phenanthrene, naphthalene and fluoranthene, respectively (Zepp and Schlotzhauer 1979). Other coal tar constituents which may undergo aqueous photolysis are acenaphthalene, anthracene, benzene, quinoline, phenol, cresol, and carbazide. In a microcosm study, PAHs leached from creosote-impregnated wood pilings were degraded in aquatic environments by photolysis and microbial degradation, while sorption to sediment was not significant (Bestari et al. 1998). Photolysis in water is not expected to be a major route of the environmental fate of creosote constituents, particularly for the less soluble compounds. 

Flyvbjerg J, Arvin E, Jensen BK, et al. 1993. Microbial degradation of phenols and aromatic hydrocarbons in creosote-contaminated groundwater under nitrate-reducing conditions. J Contain Hydrol... 

Implications of Mobility on the Availability and Degradation of Pesticides in Soil. Repeated application of 2,4-dichlorophenol, p-nitrophenol, and salicylic acid (as observed in current studies) and carbofuran phenol (20) has induced enhanced microbial degradation of their parent compounds. Rf values of these hydrolysis products indicate intermediate to high mobility in soils. The p-nitrophenol, 2,4-dichlorophenol, and salicylic acid were utilized as energy sources by microbes, and their availability in soil may contribute to the induction of rapid microbial metabolism. Carbofuran phenol did not serve as a microbial substrate but also enhanced the degradation of its parent compound, carbofuran (20). Carbofuran phenol is freely available in anaerobic soils, but the significance of its availability is yet to be understood. 

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. 

Unstable in alkaline media. Stable in acid and neutral media. Decomposes above 150°C. Most important metabolite is CO2, formed by microbiological degradation of the phenol compounds. ty2 (river water environmental conditions) 13.5 days (pH 7.5), and (pond water 26 to 30°C) 2.3 days (pH 7.8 to 8.5), and (deionized water 27 2°C) 36 days (pH 7), and (deionized water 27 2°C) 1.2 h (pH 10). ty2 (soil) 30 to 60 days Hydrolyzed slowly in acid and alkaline media. Stable to UV light. Decomposes above 150°C. In soil, microbial degradation yields 3-chloroaniline via an enzymatic hydrolysis reaction with release of CO2. ti/2 (distilled water)... 

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