Degradation, by microorganisms

Environmental Fate. A portion of releases of toluene to land and water will evaporate. Toluene may also be degraded by microorganisms. Once volatilized, toluene in the lower atmosphere will react with other atmospheric components contributing to the formation of ground-level ozone and other air pollutants. 

Environmental Fate. Most of the MEK released to the environment will end up in the atmosphere. MEK can contribute to the formation of air pollutants in the lower atmosphere. It can be degraded by microorganisms living in water and soil. 

Dissolution of gasoline compounds to soil water is a function of each compound s solubility. A highly soluble gasoline substance often has a relatively low adsorption coefficient and also tends to be more readily degradable by microorganisms,19 as shown in Table 18.1. 

Knowles, C.J. (1988) Cyanide utilization and degradation by microorganisms. Ciba Foundation Symposium, 140, 3-15. 

Keniston, R.C., S. Cabellon, Jr., and K.S. Yarbrough. 1987. Pyridoxal 5 -phosphate as an antidote for cyanide, spermine, gentamicin, and dopamine toxicity an in vivo rat study. Toxicol. Appl. Pharmacol. 88 433-441. Knocke, W.R. 1981. Electroplating and cyanide wastes. Jour. Water Pollut. Contr. Feder. 53 847-851. Knowles, C.J. 1988. Cyanide utilization and degradation by microorganisms. Pages 3-15 in D. Evered and S. 

Ehrhardt, H. M. and Rehm, H. J. (1985). Phenol degradation by microorganisms adsorbed on activated carbon, Appl. Microbiol. Biotechnol., 21, 32-36. 

Knowles CJ. 1988. Cyanide utilisation and degradation by microorganisms. In Cyanide compounds in biology, CIBA foundation symposium 140., Wiley, Chichester, 3-15. 

The principal fate of bromomethane in soil is volatilization, but some may react with organic soil constituents to yield nonvolatile end products, including bromide ion (Brown and Rolston 1980 Goring et al. 1975 Shiroishi et al. 1964). There is little evidence that bromomethane in soil is degraded by microorganisms (ERA 1986b). 

CASRN 133-90-4 molecular formula C7H5CI2NO2 FW 206.02 Soil. In soils, chloramben was degraded by microorganisms but no products were identified (Humburg et al, 1991). The main degradative pathway of chloramben in soil is decarboxylation and subsequent mineralization to carbon dioxide. The calculated half-lives in Ella loamy sand, Kewaunee clay, and Poygan silty clay were 120-201, 182-286, and 176-314 d, respectively (Wildung et al, 1968). Persistence in soil is 6-8 wk (Hartley and Kidd, 1987). 

CASRN 1982-47-4 molecular formula C15H15CIN2O2 FW 290.75 Soil Hartley and Kidd (1987) reported 4-(4-chlorophenoxy)aniline as a soil metabolite. Chloroxuron was degraded by microorganisms in humus soil and a sandy loam forming -(4-chlorophenoxy)phenyl-A-methylurea, W-(4-chlorophenoxy)phenylurea, and 4-(4-chlorophenoxy)-aniline, and two minor unidentified compounds (Geissbiihler et al., 1963). Residual activity in soil is limited to approximately 4 months (Hartley and Kidd, 1987). 

Biological. Under aerobic and anaerobic conditions, the rate of diquat mineralization in eutrophic water and sediments was very low. After 65 d, only 0.88 and 0.21% of the applied amount (5 mg/mL) evolved as carbon dioxide (Simsiman and Chesters, 1976). Diquat is readily mineralized to carbon dioxide in nutrient solutions containing microorganisms. The addition of montmorillonite clay in an amount equal to adsorb one-half of the diquat decreased the amount of carbon dioxide by 50%. Additions of kaolinite clay had no effect on the amount of diquat degraded by microorganisms (Weber and Coble, 1968). 

The formation and excretion of urea is the primary mechanism by which excess nitrogen, in the form of ammonia, is removed from the body. Surprisingly, it was found that the actual rate of urea synthesis exceeded considerably the rate of excretion of the urea. The interesting question, therefore, is what is the fate of this lost urea The answer is that urea enters the large intestine, where it is degraded by microorganisms that possess the enzyme urease, which catalyses the reaction ... 

Kawai F (2010) The biochemistry and molecular biology of xenobiotic polymer degradation by microorganisms. Biosci Biotechnoi Biochem 74 1743-1759... 

The process breaks down some contaminants into simpler compounds that can be further degraded by microorganisms. 

Diazinon released to water may be subject to both abiotic degradation (i.e., hydrolysis and photolysis) and biotic degradation by microorganisms. The rate of abiotic degradation is influenced strongly by pH and temperature. In a laboratory study, Chapman and Cole (1982) reported that pH alone influenced the half-life of diazinon maintained in sterile water-ethanol (99 1) phosphate buffer solutions at 25 °C. 

Figure 17.2 Variation in time courses of naphthalene degradation by microorganisms in laboratory soil-water incubations with 02 present ( ) or no 02 present (o). Data from Mihelcic and Luthy, 1988.

RDX had previously resisted degradation by microorganisms, until a microbial system containing a purple photosynthetic bacteria was found to degrade RDX. The hypothesis is advanced that the RDX molecule is not actually metabolized, but is reduced and modified as a result of the active electron transfer brought about by the anaerobic photosynthetic activity... 

The com stalk wastes used as substrate were obtained from the suburbs of Amman city. Before the substrate were degraded by microorganisms, the mixture of com stalk and dilute HC1 (or NaOH) solution was boiled 30 min in beakers, and then neutralized to pH = 7 with either dilute NaOH or HC1 solution. TVS value was determined as follows ... 

Branched chain syndets are less easily degraded by microorganisms in the environment than unbranched syndets. Therefore, it is for environmental reasons that syndets have mostly unbranched alkyl chains. 

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