Degradation, anaerobic

Anaerobic slurry reactors have recently been developed to treat soil contaminated with compounds such as trinitrotoluene (TNT) and other munitions compounds that are more readily degraded anaerobically than aerobically. The time frame for... 

Zindel U., Freudenberg W., Rieth M., Andreesen 1. R., SchneU L, and Widdel F. (1988) Eubacterium acidaminophilum sp. nov., a versatile amino acid-degrading anaerobe producing or utilizing H2 or formate description and enzymatic studies. Arch. Microbiol. 150, 254-266. 

Compounds with a high oxidation state such as those with a lot of chlorine are recalcitrant to further oxidation. These compounds must therefore be degraded anaerobically. Chlorine is substituted by hydrogen or HC1 is removed and a double bond is introduced, for example, DDT that may be dechlorinated to 4,4 -dichlorodiphenyl-dichloroethane (DDD) by anaerobic processes or slowly converted to 4,4 -dichlorodiphenyldichloroethylene (DDE) (Stenersen, 1965). Compounds such as mirex and hexachlorobenzene are extremely recalcitrant to degradation, and microorganisms do not attack the highly fluorinated or chlorinated polymers, such as Teflon and PVC. 

Aromatic compounds can also be degraded anaerobically, via reductive pathways, which have been reviewed. The best-characterized example is the degradation of benzoic acid in Rhodopseudomonas palustris and Thauera aromatica via the pathway shown in Figure 8. Benzoyl-CoA is formed, and then a reductase enzyme is able to reduce the aromatic ring to a cyclohexadiene. Following two consecutive additions of water, and oxidation to a /3-keto ester, hydrolytic cleavage gives a linear 7-carbon CoA thioester, which can then be broken down via fatty acid /3-oxidation. 

Under aerobic conditions, glucose oxidation by the cortex produces very little lactic acid. Under anaerobic conditions glycolysis sets in, and lactic acid is produced with great rapidity. Brain cortex shows a typical Pasteur effect, in that the quantity of glucose degraded anaerobically is relatively greater than the quantity oxidised under aerobic conditions. 

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