Biochemical Microbial Reductions

Two most common enzymatic systems are yeast alcohol dehydrogenase (YAD) and horse liver alcohol dehydrogenase (HLADH). The selectivity 

It was shown that the selectivity of reduction changed from (S) selectivity with small chain esters to (R) selectivity with long chain esters.  

The selectivity of reduction is also illustrated by the observation that 

The above examples illustrate the enantioselectivity of the reduction and that selectivity depends on the size and nature of the groups around the carbonyl. 

The selectivity of all these reductions is in consistent with the (S)-selectivity as predicted by Prelog s rule. It is found that 1,3-diketones are normally reduced to P-ketoalcohol. Thus, 2,4-hexanedione gave quantitatively (S)-5-hydroxy- 

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Kathiravan MN, Karthick R, Muthu N, Muthukumar K, Velan M (2010) Sonoassisted microbial reduction of chromium. Biochem Biotechnol 160(7) 2000-2013... 

The nitrogenase enzymes are the sole mediators of biological nitrogen fixation, the microbial reduction of dinitrogen to ammonia. The enzymatic conversion entails the intervention of a set of biometalloclusters with distinctive, often unique, properties. The enzyme system is complex and particularly resistant to biochemical and biophysical analysis at the molecular level, and the clusters themselves have very limited synthetic precedent in form and reactivity. As a result, a comprehensive chemical understanding of the nitrogenase clusters remains elusive despite decades of study. 

Microbial reduction of ethyl acetoacetate to ethyl (R)-3-hydroxybutyrate in an ionic liquid containing system. Process Biochem., 44, 316-321. 

The extension of the useful storage life of plant and animal products beyond a few days at room temperature presents a series of complex biochemical, physical, microbial, and economic challenges. Respiratory enzyme systems and other enzymes ia these foods continue to function. Their reaction products can cause off-davors, darkening, and softening. Microbes contaminating the surface of plants or animals can grow ia cell exudates produced by bmises, peeling, or size reduction. Fresh plant and animal tissue can be contaminated by odors, dust, iasects, rodents, and microbes. 

Biochemical waste transformation occurred at low waste concentrations, resulting in the production of methane. Additional microbial degradation of the waste resulted in the reduction of sulfates to sulfides and ferric ions to ferrous ions. 

Ader M, Chaudhuri S, Coates JD, Coleman M (2008) Microbial perchlorate reduction a precise laboratory determination of the chlorine isotope fractionation and its possible biochemical basis. Earth Planet Sci Lett 269 604-612... 

A number of 5-nitro-2-furaldehyde derivatives, called nitrofurans, are used in the treatment and/or prophylaxis of microbial infections, primarily in the urinary tract. Recent evidence suggests that the reduction of the 5-nitro group to the nitro anion results in bacterial toxicity. Intermediate metabolites modify various bacterial macromolecules that affect a variety of biochemical processes (e.g., DNA and RNA synthesis, protein synthesis) this observation may explain the lack of resistance development to these drugs. Evidence also indicates that the nitro anion undergoes recycling with the production of superoxide and other toxic oxygen compounds. It is presumed that the nitrofurans are selectively toxic to microbial cells because in humans, the slower reduction by mammalian cells prevents high serum concentrations. 

In situ reductive dechlorination has been cited as an important pathway for biochemical weathering of PCBs in sediments (2, 5). The reductive dechlorination hypothesis is based on the premise that microbial action on PCB congeners is sterically selective for the chlorines in the meta and para positions on the biphenyl rings (i.e., 3, 3, 4, 4, 5, and/or 5 ). Such selectivity would result in the cleaving of the chlorines in these positions (5). If this process occurs, the terminal dechlorination products of the microbially resistant ortho-substituted congeners in the anaerobic environment should be 2,2 -DCB, 2,6-DCB, 2,2, 6-TrCB, and 2,2, 6,6 -TCB. Thus, the weight... 

Bakker, A.W., Schippers, B. Microbial cyanide production in the rhizosphere in relation to potato yield reduction and Pseudomonas spp. - mediated plant growth-stimulation. Soil Biol Biochem 1987 19 451-57. 

Clein, I. S., and Schimel, ). R (1994). Reduction in microbial activity in birch litter due to drying and rewetting events. Soil Biol. Biochem. 26, 403-406. 

Schmidt, E., Blaser, H.U., Fauquex, P.F., Sedelmeier, G., and Spindler, F. Comparison of Chemical and Biochemical Reduction Methods for the Synthesis of (R)-2-Hydroxy-4-phenylbutyric Acid. In Microbial Reagents in Organic Synthesis, Servi, S. (ed.) Kluwer Academic Publishers Amsterdam, 1992, pp. 377-388. 

The number of species involved here (MeHg, Me2Hg, Hg and Hg(0)) is small relative to those of some other elements (e.g., arsenic), with only the counterion varying. In the aquatic environment, methylmercury may be present coordinated to chloride, hydroxide, alkanethiol, or various other forms of organic material, either dissolved or in the solid phase. Coordination depends on competition between chemical, biochemical, pH or Eh (oxidation levels), and salinity. Reduction to inorganic mercury or further slow methylation to dimethylmercury may occur (this latter may lead to transport to the atmosphere). Similarly, coordinated methylmercury may enter the sediment layer. This latter may be considered as the main zone for microbial methylation of Hg in view of the high amount of biological activity there. Similar coordination may exist as in the aquatic zone, but with more likelihood of sulfide or alkanethiol complexation. 

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