Facultatively anaerobic microorganisms

Many contaminants contain nitrogen, phosphorus, or sulfur, and degradative organisms may utilize one or more of these leaving the major part of the substrate intact. This is particularly important for munitions-related compounds with a high N/C ratio, when the addition of carbon sources may lead to the favorable development of anaerobic or facultatively anaerobic microorganisms. 

The most critical issue to be investigated during the initial biofeasibility study is the determination of which metabolic mode—aerobic or anaerobic—is more appropriate for the specific contaminants. As shown in Table 14.5, the redox potential is closely related to the metabolic mode, and careful control of this parameter is required to maintain the optimum metabolic mode during bioremediation. A general rule is that the redox potential should be above 50 mV to maintain the activity of aerobic and facultative anaerobic microorganisms and below that value for strictly anaerobic m icroorganisms.12... 

Yeasts are facultative anaerobic microorganisms because they possess the genetic equipment for metabolizing sugars aerobically or anaerobically (Boulton et al. 1996). Therefore, yeasts can consume sugars using two different metabolic pathways respiration and fermentation (Racker 1974). Figure 1.3 illustrates these biochemical pathways. 

Highly chlorinated PCBs and pesticides (e.g., mirex and DDT) may be dechlorinated anaerobically by functioning as an electron acceptor. DDT is dechlorinated to DDD by many facultative anaerobic microorganisms under anoxic conditions. DDD can be further dechlorinated or degraded aerobically. 

Test organism aerobic and facultative anaerobic microorganisms in the soil. Principle/Procedu re The substrate-induced microbial respiratory activity of the soil is determined. 

Facultative anaerobes microorganisms that make adenosine triphosphate (ATP) by aerobic respiration if oxygen is present, but are also capable of growing by fermentation in the absence of oxygen. 

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