Aerobic conditions

A reductase in Escherichia coli can reduce V-ethylmaleamide to V-ethylsuccinimide (Miuraetal. 1997). 

Morphinone can be reduced by Pseudomonas putida MIO to hydromorphone using an enzyme of which one of the subunits contains FMN (French and Bruce 1994). 

The reductase from Burkholderia sp. strain WS produces (5)-2-chloropropionate from 2-chloroacrylate (Kurata et al. 2005). 

An enzyme that catalyzes the reduction of A -piperidein-2-carboxylate to piperidine-2-car-boxylate (r-pipecolate) in the catabolism of o-lysine by Pseudomonas putida ATCC12633 is an NADPH-dependent representative of a large family of reductases that are distributed among bacteria and archaea (Muramatsu et al. 2005). It also catalyzes the reduction of A -pyrrolidine-2-carboxylate to L-proline. 

Important reductions are involved in the anaerobic transformations of steroid and flavanoids  

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Bloremedia.tlon. Cmde oil and refined products are readily biodegradable under aerobic conditions, but they are only incomplete foods siace they lack any significant nitrogen, phosphoms, and essential trace elements. Bioremediation strategies for removing large quantities of hydrocarbon must therefore iaclude the addition of fertilisers to provide these elements la a bioavailable form. 

RDX and HMX are rather more recalcitrant, especially under aerobic conditions, but there are promising indications that biodegradation can occur under some conditions, especially composting (67). Several strains of bacteria able to use RDX (and Triazine) as a sole source of nitrogen for growth have recentiy been isolated, and this is an area where rapid progress is being made. 

The function of aeration in a wastewater treatment system is to maintain an aerobic condition. Water, upon exposure to air, tends to estabUsh an equihbrium concentration of dissolved oxygen (DO). Oxygen absorption is controlled by gas solubiUty and diffusion at the gas—hquid interface. Mechanical or artificial aeration may be utilised to speed up this process. Agitating the water, creating drops or a thin layer, or bubbling air through water speeds up absorption because each increases the surface area at the interface. 

Xanthan Gum. Xanthan gum [11138-66-2] is produced by industrial fermentation of a carbohydrate under aerobic conditions by culturing the... 

Microorganisms requite several minerals such as ferrous and potassium ions which play important roles in glutamic acid fermentation. Other important culture conditions include regulating aeration stirring. The biosynthesis of L-glutamic acid is performed under regulated aerobic conditions. 

Reductive DechIorina.tion. Such reduction of chlorinated aUphatic hydrocarbons, eg, lindane, has been known since the 1960s. More recentiy, the dechlorination of aromatic pesticides, eg, 2,4,5-T, or pesticide products, eg, chlorophenols, has also been documented (eq. 10) (20). These reactions are of particular interest because chlorinated compounds are generally persistent under aerobic conditions. 

Aerobic, Anaerobic, and Combined Systems. The vast majority of in situ bioremediations ate conducted under aerobic conditions because most organics can be degraded aerobically and more rapidly than under anaerobic conditions. Some synthetic chemicals are highly resistant to aerobic biodegradation, such as highly oxidized, chlorinated hydrocarbons and polynuclear aromatic hydrocarbons (PAHs). Examples of such compounds are tetrachloroethylene, TCE, benzo(a)pyrene [50-32-8] PCBs, and pesticides. 

In the two-stage process, nitrification occurs under aerobic conditions in the second stage. The nitrified mixed Hquor from the second stage is internally recycled to the anoxic first stage, where denitrification occurs. 

For aeration, diffused-air or mechanical units are used. Air diffusers are commonly used ia North America, but some mechanical aeration units are iastalled ia plants with capacities >3, 800 /d (10 gal/d). Aeration transfers oxygen to the sewage and maintains aerobic conditions, mixes sewage and floe, and keeps the floe ia suspension. 

With respecd to item 1, bacterial decomposition initially occurs under aerobic conditions because a certain amount of air is trapped within the landfill. However, the oxygen in the trapped air is e diausted within days, and long-term decomposition occurs under anaerobic conditions. 

Wastes spread on the surface should he disked or plowed into the soil soon after apphcation (1 to 7 days). To promote aerobic conditions and rapid hioconversion of the wastes the soil-waste mixture should he cultivated periodically. 

These bacteria are anaerobic. They may survive but not actively grow when exposed to aerobic conditions. They occur in most natural waters including fresh, brackish, and sea water. Most soils and sediments contain sulfate reducers. Sulfate or sulfite must be present for active growth. The bacteria may tolerate temperatures as high as about 176°F (80°C) and a pH from about 5 to 9. 

BOD Biochemical Oxygen Demand - the rate at which microorganisms use the oxygen in water or wastewater while stabilizing decomposable organic matter under aerobic conditions. In decomposition, organic matter serves as food for the bacteria and energy results from this oxidation. 

Digester A tank in which sludge is placed to allow decomposition by microorganisms. Digestion may occur under anaerobic (most common) or aerobic conditions. 

Facultative anaerobe A bacterium capable of growing under aerobic conditions or anaerobic conditions in the presence of an inorganic ion ie. SO4, NO3. 

Aerobic reactor A reaction vessel operating under aerobic conditions with sterile air being used as the source of oxygen in dissolved state. 

Glycolysis and the citric acid cycle (to be discussed in Chapter 20) are coupled via phosphofructokinase, because citrate, an intermediate in the citric acid cycle, is an allosteric inhibitor of phosphofructokinase. When the citric acid cycle reaches saturation, glycolysis (which feeds the citric acid cycle under aerobic conditions) slows down. The citric acid cycle directs electrons into the electron transport chain (for the purpose of ATP synthesis in oxidative phosphorylation) and also provides precursor molecules for biosynthetic pathways. Inhibition of glycolysis by citrate ensures that glucose will not be committed to these activities if the citric acid cycle is already saturated. 

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