Electron Acceptors Other than Oxygen

PART 2 ELECTRON ACCEPTORS OTHER THAN OXYGEN 

Bacteria can use a range of electron acceptors in the absence of oxygen. Although they are able to reduce a number of oxyanions, only a limited number of these can support growth under anaerobic conditions by coupling reduction to the production of energy by proton translocation. A number 

The conditions under which these function and their regulation depend on the organism. For example, in Escherichia coli, oxygen represses the synthesis of the other reductases, and under anaerobic conditions the reductases for fumarate, DMSO, and TMAO are repressed by nitrate. This does not apply to Wolinella succinogenes in which sulfur represses the synthesis of the more positive electron acceptors nitrate and fumarate (Lorenzen et al. 1993). The DMSO reductase from Escherichia coli (Weiner et al. 1988) has a broad substrate versatility, and is able to reduce a range of sulfoxides and A-oxides. Anaerobic sulfate reduction is not discussed here in detail. 

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Anaerobic Lives in the absence of oxygen and uses electron acceptors, other than oxygen (i.e., nitrogen and carbon)... 

Enhancement of Biodegradation by Electron Acceptors Other Than Oxygen... 

A search for organisms with novel metabolic and bioenergetic pathways, particularly pathways involved in carbon dioxide and carbon monoxide reduction and methane oxidation coupled with electron acceptors other than oxygen ... 

Other oxidoreductases (dehydrogenases) use electron acceptors other than oxygen, such as the cofactor NAD or NAD(P)". These cofactors maybe advan-t eously combined with electrochemical sensors, provided that the cofactor is externally supplied or immobilized and regenerated. More than 250 highly specific dehydrogenases are commercially available. Hydrolases are another class of readily available enzymes that can be combined with potentiometric sensors. Hydrolases catalyse the hydrolytic cleavage of C-O, C-N, C-C, and other bonds. Other biosensors can be fabricated from the new generation of hybrid and synthetic enzymes (17). 

Electron acceptors other than oxygen can serve as mediators in the glucose oxidase reaction, and completely eliminate any dependence of the amperometric response on oxygen concentration of the sample. The mediator, usually CO-immobilized with the enzyme, transports electrons to the... 

Organisms Using Electron Acceptors Other than Oxygen... 

In all cases, the ratio of aerobic to anaerobic decomposition ranges from 3 to 6. Anaerobic decomposition in these systems represents a combined effect of alternate electron acceptors. Anaerobic conditions here represent a combined effect of several alternate electron acceptors (other than oxygen) present on organic matter decomposition. As mentioned previously, typically all wetlands are limited in electron acceptors, whereas electron donors are nonlimiting in most wetlands. Annual carbon loss due to decomposition processes varied between 0.7 and 3.7% of total carbon in the top 24 cm soil from four freshwater wetlands in the southeastern United States (Schipper and Reddy,... 

Photosensltlzatlon by electron transfer, as shown In equation 2 above, has also been observed (22,23). The occurrence of 0 (14,16) In natural waters Is good evidence that these processes are occurring, at least for oxygen reduction. With electron acceptors other than oxygen, this process Is probably similar to energy transfer in that there is a low probability for other electron acceptors to be Involved except in heterogeneous environments. 

MFCs with electron acceptors other than oxygen... 

Using electron acceptors other than oxygen can produce power, but chemicals need to be regenerated. Two different approaches have been taken to try to use metals as the electron acceptor in an MFC. One approach used by Shantaram et al. (2005) and Rhoads et al. (2005) was based on using a solid-state cathode made of manganese oxide. Mn02 is... 

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