Microbial Oxidations with

Enzymic asynmietric epoxidation of alkenes may be performed by pure monooxygenases. However, due to practical problems such as need of cofactors, microbial oxidation with whole cells has been more widely used for the purpose. One great disadvantage however, is the toxicity of epoxides towards living cells. 

The efSciency of the present reaction has been demonstrated by the synthesis of cortisone acetate 49, which is a valuable anti-inflammatory agent. The oxidation of 3/3,21-diacetoxy-5a-pregn-17-ene (47) proceeds stereoselectively to give 20-oxo-5a-pregnane-3/3,17a,21-triol 3,21-diacetate (48) (57%) (Eq. 3.68). Conventional treatment of 48 followed by microbial oxidation with Rhizopus nigricaus gave cortisone acetate 49 [128]. 

Microbial Oxidations with P450s for Synthesis of Pharmaceuticals... 

Gestodene has been prepared in several ways (85). The route that provides the highest yield is shown in Eigure 8. Microbial oxidation of (55) with Penicillium raistrickii results in the 15-alcohol (56). Protection of the alcohol as the acetate (57) and protection of the ketone as a dienolether provides (58). In a one-pot procedure (58) is treated with lithium acetyUde and subjected to a hydrolytic work-up to provide gestodene (54) (86). 

In the olivanic acid series of carbapenems the ( )-acetamidoethenyl grouping can be isomerised to the (Z)-isomer (19) (22) and reaction with hypobromous acid provides a bromohydrin that fragments to give a thiol of type (20) when R = H, SO H, or COCH. The thiol is not isolated but can react to provide new alkyl or alkenyl C-2 substituents (28). In the case of the nonsulfated olivanic acids, inversion of the stereochemistry at the 8(3)-hydroxyl group by way of a Mitsunobu reaction affords an entry to the 8(R)-thienamycin series (29). An alternative method for introducing new sulfur substituents makes use of a displacement reaction of a carbapenem (3)-oxide with a thiol (30). Microbial deacylation of the acylamino group in PS-5 (5) has... 

FIGURE 10.51 Transformation of benzothiophene involving microbial oxidation and chemical reaction of the sulfoxide. (From Neilson, A.H. and Allard, A.-S., The Handbook of Environmental Chemistry, Vol. 3J, pp. 1-80, Springer, Heidelberg, 1998. With permission.)... 

We take two cases in which mineral surfaces catalyze oxidation or reduction, and one in which a consortium of microbes, modeled as if it were a simple enzyme, promotes a redox reaction. In Chapter 33, we treat the question of modeling the interaction of microbial populations with geochemical systems in a more general way. 

The following exemplifies how the total balance of a redox reaction is completed taking an electron donor and an electron acceptor (cf. the outline of the total redox reaction in Figure 2.3). Example 2.2 is, in this respect, used as an example of an (microbial) oxidation of an electron donor (organic matter) under anoxic conditions, i.e., with reduction of NO3 as electron acceptor (cf. Example 2.4). 

In contrast to asymmetric oxidation of unsymmetrical sulfides with chiral peracids, microbial oxidation usually gives much better results. Thus, optically active phenyl benzyl sulfoxide was prepared by oxidation of the parent sulfide via fermentation with Aspergillus niger, NRRL 337, with 18% optical purity (42). Similarly, asymmetric... 

Transport of O2 away from a root and its consumption in microbial processes—in addition to nitrification—and oxidation of mobile reductants such as Fe +. Microbial O2 consumption is described with Michaelis-Menten kinetics and Fe + oxidation with first-order kinetics with respect to both... 

Microbial deoxygenation of benzo[f]cinnolin-5-ium oxide with Bakers yeast-NaOH in EtOH/water at reflux yielded 90% of benzo[f]cinnoline <1997TL845>. The same deoxygenation has been achieved in a similar yield via heating in EtOH with NaOEt at 160°C in a sealed tube <2004JOC7720>. 

Similarly, catechin polymers formed upon horseradish peroxidase-catalyzed oxidation of catechin or polycondensation of catechin with aldehydes prove much more efficient than catechin (at identical monomer concentration) at inhibiting XO and superoxide formation. A more detailed investigation with the catechin-acetaldehyde polycondensate (which is expected to form in wine because of the microbial oxidation of ethanol to acetaldehyde) shows that inhibition is noncompetitive to xanthine and likely occurs via binding to the FAD or Fe/S redox centers involved in electron transfers from the reduced molybdenum center to dioxygen with simultaneous production of superoxide. 

Hilker, I., Wohlgemuth, R., Alphand, V. and Eurstoss, R. Microbial Transformations 59 First Kilogram Scale Asymmetric Microbial Baeyer-Villiger Oxidation with Optimized Productivity Using a Resin-based in situ SFPR Strategy. Biotechnol. Bioeng. 2005, 92, 702-710. 

Asymmetric microbial oxidation afforded the (-)-epoxide which has been explored as a building block ring opening reactions with organometallic nucleophiles, and via Friedel-Crafts reactions have been reported. [226,227]. A non-biotransformative approach to this epoxide has also been described [228]. Copper(II)-catalysed oxidative hydrolysis (Eq. 72) affords a lactic acid analogue in high enantiomeric purity [229]. 

Heap (dump) acid leaching of copper sulfide ores is possible with the aid of microbial oxidation. Not all copper minerals are sulfidic, however— malachite, azurite, and chrysocolla are basic copper carbonates—and sulfuric acid heap leaching of low-grade copper carbonate ores can give solutions from which the Cu2+ ion can be separated by solvent extraction (Section 17.3) and copper metal obtained by electrowinning. 

Calculate the steady-state output trichloroethene concentration (/tM) after the methanotrophs have increased their biomass to a steady state level (cell-m-3) assuming a tank with a volume of either V= 10 m3 or 50 m3. Assume you have a waste water flow, Q, of 5 m3 d l, a microbial inoculum with growth properties like those shown in Table 17.6 for the landfill-derived methane oxidizers, and a die-off coefficient b of 0.1 d . 

Oxidation of Reduced S. Indirect evidence suggests that microbial oxidation of sulfide is important in sediments. If it is assumed that loss of organic S from sediments occurs via formation of H2S and subsequent oxidation of sulfide to sulfate (with the exception of pyrite, no intermediate oxidation states accumulate in sediments cf. 120, 121), the stated estimates of organic S mineralization suggest that sulfide production and oxidation rates of 3.6-124 mmol/m2 per year occur in lake sediments. Similar estimates were made by Cook and Schindler (1.5 mmol/m2 per year 122) and Nriagu (11 mmol/m2 per year 25). A comparison of sulfate reduction rates (Table I) and rates of reduced S accumulation in sediments (Table III) indicates that most sulfide produced by sulfate reduction also must be reoxidized but at rates of 716-8700 mmol/m2 per year. Comparison of abiotic and microbial oxidation rates suggests that such high rates of sulfide oxidation are possible only via microbial mediation. 

Gihring, T.M., Edwards, K.J., Bond, P.L. et al. (1999) Microbial interactions with arsenopyrite during oxidative dissolution. Abstracts with Programs. The Geological Society of America, 31(7), 448. 

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