Biodegradative pathways

Exposure studies have been made using mice and rats (257). These experiments have demonstrated species differences in butadiene toxicity and carcinogenicity. Butadiene was found to be a potent carcinogen in the mouse, but only a weak carcinogen in the rat. The interpretations have focused on differences in toxification rates and detoxification metaboHsms as causative factors (257). The metaboHsm is beHeved to proceed through intermediates involving butadiene monoepoxide and butadiene diepoxide (257). A similar mechanism has been proposed for its biodegradation pathway (258). 

Nelson MJK, Montgomery SO, Mahaffey WR, et al. 1987. Biodegradation of trichloroethylene and involvement of an aromatic biodegradative pathway. Appl Environ Microbiol 53 949-954. 

Coleman NV, JC Spain (2003) Epoxyalkane coenzyme M transferase in the ethene and vinyl chloride biodegradation pathways of Mycobacterium strain JS60. J Bacterial 185 5536-5546. 

May be difficult to implement in low-permeability aquifers Reinjection wells or infiltration galleries may require permits or may be prohibited Biodegradation pathways may be site-specific, potentially requiring pilot testing or treatability studies A relatively large amount of oxidant may be needed for treatment of large contaminant mass... 

Electron donors—In direct biodegradation pathways, the contaminant acts as the electron donor or substrate. However, during cometabolic degradation, a different electron donor is metabolized, resulting in the consequential oxidation of the contaminant. In some contaminated plumes, other electron donors, such as other constituents of gasoline, may also be present. In cases where they are not, and cometabolic degradation pathways are desired, electron donors may be added. 

These factors affect the design of the bioremediation system, the biodegradation pathways that can be employed, and the amendments that must be added to enhance bioremediation.34 40... 

Spence MJ, Bottrell SH, Thornton SI, Richnow HH, Spence KH (2005) Hydrochemical and isotopic effects associated with petroleum fuel biodegradation pathways in a chalk aquifer. J Con... 

Fig. 5.1.14. (a) Generally proposed aerobic biodegradation pathway of NPEO. [122] (b) Newly proposed aerobic biodegradation pathway [40], With permission from Env. Sci Technol, by the American Chemical Society, 2001. 

Pig. 5.1.21. Proposed biodegradation pathways for aliphatic alcohol polyethoxylates under aerobic conditions (taken from Ref. [137]). With permission from Analusis., by EDP Sciences, 1997. 

Fig. 21. Aerobic biodegradation pathways of aromatic compounds by bacteria and fungi...

Masunaga, S., Urushigawa, Y., and Yonezawa, Y. Biodegradation pathway of o-cresol by heterogeneous culture. Water Res., 20(4) 477-484, 1986. 

Fig. 13.7 Generalized aerobic and anaerobic biodegradation pathways for n-alkanes. Reprinted from Abrajano TA, Yan B, O Malley V (2005) High molecular weight petrogenic and pyrogenic hydrocarbons in aquatic environments In Drever JI (ed) Surface and ground water, weathering and soils vol 5 Treatise on Geochemistry pp 475-509. Copyright 2005 with permission of Elsevier...

University of Minnesota Biocatalysis/Biodegradation Database (umbbd.ahc.umn.edu) can be used to predict biodegradation pathways and biodegradation metabolites. Approximately two-thirds of the hazardous substances mentioned in the CERCLA Priority List of Hazardous Substances can be treated by different biotechnological methods. 

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