Bacteria degrading

Endosulfan in aqueous solutions is also expected to undergo biodegradation. In laboratory tests at pH 7 and 20 , Pseudomonas bacteria degraded endosulfan (isomers not specified) under aerobic conditions with a half-life of about 1 week (Greve and Wit 1971). Biotic and abiotic transformations of endosulfan in seawater/sediment microcosms have been reported (Gotham and Bidleman 1989). In biotic tests, half-lives for the a- and P-isomers in seawater-only microcosms (pH 8) were about 5 and 2 days, respectively. In seawater-only microcosms under sterile conditions at a pH of 8 or higher, the half-life for the a-isomer was 2-3 days, whereas the half-life for the p-isomer was 1-2 days. Half-lives were longer in seawater/sediment microcosms, possibly because of the lower pHs (7.3-7.7) in these test systems half-lives were 22 and 8.3 days for the a- and P-isomers, respectively. Endosulfan diol was the main metabolite identified. 

Table 1. Specific affinities, a , of selected bacteria degrading hydrocarbons and aromatic compounds...

The Biotrol system is comprised of two parts (1) a suspended-growth culture vessel and (2) a bioreactor that is fed with contaminated groundwater and effluent from the culture vessel. From the culture vessel, the bacteria are transferred to the bioreactor and contacted with contaminated water. The bacteria degrade contaminants within the bioreactor. 

Xenobiotic compounds are usually attacked by enzymes whose primary function is to react with other compounds, a process that provides neither carbon nor energy called cometabolism. Cometabolism usually involves relatively small modifications of the substance that is cometabolized (the secondary substrate), compared to the primary substrate. The enzymes that carry out cometabolism tend to be relatively nonspecific. As an environmentally significant example of cometabolism, at least one strain of bacteria degrades trichloroethylene with an enzyme system that acts predominantly on phenol. The enzyme activity can be induced by exposure to phenol, after which it acts on trichloroethylene. 

In pine, it was found that Bacillus polymyxa was the major species involved (45, 55), whereas, in spruce the major species were Bacillus subtilis and Flavobacterium pectinovorum (49). In another study (53), Clostridium omelianskii was identified as the species attacking softwoods. In all studies, it was found that the bacterial attack on the pit membranes was the reason for increased permeability of the wood. Furthermore, it was shown by Fogarty and Ward (49) that bacteria degraded the pit membranes by excreting the enzymes amylase xylanase, and pectinase. A typical sapwood pit membrane that has been attacked by bacteria is shown in Figure 2. As can be seen, the torus is severely degraded and has well defined openings. 

In addition, the mucosal surface of the intestine is essential for the assimilation of antigens. Proteases of the intestinal bacteria degrade the antigenic structure, an important step in the introduction of unresponsiveness to dietary antigens. Specialized antigen transport mechanisms take place in different lymphoid compartments mesenteric lymph nodes, Peyer s patches, isolated lymph follicles, isolated T lymphocytes in the epithelium and the lamina propria, as well as at the secretory sites (Heyman et al. 1982). The secretory IgA antibodies in the gut are part of the... 

Gauthier, E., Deziel, E., Villemur, R. et al. (2003). Initial characterization of new bacteria degrading high-molecular weight polycyclic aromatic hydrocarbons isolated from a 2-year enrichment in a two-liquid-phase culture system. Journal of Applied Microbiology, 94, 301-11. 

Faller, J. Hiihnerfuss, H. Kdnig, W.A. Rrebber, R. Ludwig, P., Do marine bacteria degrade a-hexachlorocyclohexane stereoselectively Environ. Sci. Technol. 1991, 25, 676-678. 

The injection scheme was optimized by simnlation using the modified UTCHEM 6.0. The final selected formula was 2% NaC03 + 1000 mg/L 1175A. The simulation results showed that the performance from different injection sequences was similar for the same mass of chemicals. Operation experience shows that polymer viscosity would be reduced by about 50% from the surface to the wellbore by mechanical shear loss, iron effect, and bacteria degradation. Therefore, in the performance prediction, the viscosity was assumed to be 50% of the measured viscosity in the laboratory. Economic analysis was also included in the optimization process to select the best injection scheme. 

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