Carboxylic acids microbial degradation

Decarboxylation designates the loss of a carboxyl group, as a result of enzymatic microbial activity. For example, the carboxyl group of aliphatic carboxylic acids differentially degrades the molecule (Fig. 15.4). In a subsurface environment characterized by extensive microbial activity, catalytic decarboxylations for both naturally occurring and exogenous organic compounds may occur. 

The application of substrates isotopically labeled in specific positions makes it possible to follow the fate of individual atoms during the microbial degradation of xenobiotics. Under optimal conditions, both the kinetics of the degradation, and the formation of metabolites may be followed— ideally when samples of the labeled metabolites are available. Many of the classical studies on the microbial metabolism of carbohydrates, carboxylic acids, and amino acids used radioactive... 

Schmidt M, P Roger, F Lingens (1991) Microbial metabolism of quinoline and related compounds XL Degradation of quinoline-4-carboxylic acid by Microbacterium sp. Hj, Agrobacterium sp. IB and Pintelo-bacter simplex 4B anf 5B. Biol Chem Hoppe-Seyler 370 1015-1020. 

Matsumura and Bousch (1966) isolated carboxy lest erase (s) enzymes from the soil fungus Trichoderma viride und a bacterium Pseudomonas sp., obtained from Ohio soil samples, that were capable of degrading malathion. Compounds identified included diethyl maleate, desmethyl malathion, carboxylesterase products, other hydrolysis products, and unidentified metabolites. The authors found that these microbial populations did not have the capability to oxidize malathion due to the absence of malaoxon. However, the major degradative pathway appeared to be desmethylation and the formation of carboxylic acid derivatives. 

The microbial degradation of nitriles can occur via two different enzymatic pathways [39], different from cyanogenesis [40] (i) nitrilase (EC 3.5.5.1) catalyzes the direct hydrolysis of nitriles to the corresponding carboxylic acids and ammonia (Eq. 1) [41] and (ii) nitriles are catabolized in two stages - they are first converted to the corresponding amides by nitrile hydratase (EC 4.2.1.84) (Eq. 2), and then to the acids and ammonia by amidase (Eq. 3). The microbial degradation of nitriles has also been reviewed elsewhere [42-45]. 

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. 

ER Blakley The microbial degradation of cyclohexane carboxylic acid a pathway involving aromatization to form / -hydro ybcnzoic acid. Can J Microbiol 20 1297-1306, 1974. 

Whereas studies on the environmental photochemistry of the majority of pesticides have been conducted extensively, few data exist for PPCPs. Pharmaceuticals are mainly polar compounds containing acidic or basic functional groups (such as carboxylic acids, phenols, and amines) that may be subject to direct and indirect photolysis. Although microbial degradation in waters and soil has been reported for pesticides, less work is reported for PPCPs. The result of such processes can be a complex mixture of reactive intermediates and TPs. Their identification represents a more challenging task than the identification of transformation products stemming from microbial transformation, for which at least some common mechanisms are well established. Therefore, the application of advanced instrumental techniques is of crucial importance. 

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