Reduction reaction, microbial

Fig. 2. Oxidation and reduction reactions using microbial transformation for steroid synthesis.

Reductive reactions typically occur in anaerobic environments where there is an abundant supply of electron donors. Electron donors are typically of microbial origin, eg, porphyrins or cysteine, which sometimes leads to confusion regarding the nature, ie, chemical vs enzymatic, of the reductive reaction. By definition, all reductive reactions which are not enzymatically catalyzed are chemical. The most significant chemical reductive reaction is reductive dechlorination. 

Vorbeck C, H Lenke, P Fischer, JC Spain, H-J Knackmuss (1998) Initial reductive reactions in aerobic microbial metabolism of 2,4,6-trinitrotoluene. Appl Environ Microbiol 64 246-252. 

Fuel cell applications Manganese dioxide as a new cathode catalyst in microbial fuel cells [118] OMS-2 catalysts in proton exchange membrane fuel cell applications [119] An improved cathode for alkaline fuel cells [120] Nanostructured manganese oxide as a cathodic catalyst for enhanced oxygen reduction in a microbial fuel cell [121] Carbon-supported tetragonal MnOOH catalysts for oxygen reduction reaction in alkaline media [122]... 

A third prominent set of biologically mediated reactions used for the initial transformations of xenobiotic compounds are reductions. As discussed in Chapter 14, reduction reactions entail transferring electrons to the organic compound of interest. Microbially mediated reductive transformations involve the same structural moieties that are susceptible to abiotic reductions (Table 17.5). The common characteristic for the structures at the point of reduction is that electron-withdrawing... 

These processes are catalyzed by bacteria and probably involve both inorganic and organic iron and manganese species (22). They may also be strongly controlled by microbial competition between Fe(III) and sulfate-reducing bacteria (27). Associated with these reduction reactions is the reduction of residual sulfate (produced in the oxic zone by bacterially catalyzed reactions) similar to eq 7 (21). 

The design rules for fermentative metabolism in bacteria are few in number and are widely expressed in the microbial world. Firstly, the fermentation process always involves the partial oxidation of substrate, although there is a tremendous diversity in choice of substrate. Almost any organic compound can be fermented by some microorganism somewhere. Secondly, the oxidative reaction or reactions must always be balanced by subsequent reductive reactions in order to allow sustained func-... 

The time-dependent transformation of N compounds by microbial oxidation and reduction reactions can also be described by Michaelis-Menten rate expression... 

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