Nitrogen aerobic

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. 

When organics containing reduced nitrogen are degraded, they usually produce ammonium, which is in equilibrium with ammonia. As the pK for NH3 NH4" is 9.3, the ammonium ion is the primary form present in virtually all biological treatment systems, as they operate at pH < 8.5 and usually in the pH range of 6.5-7.5. In aerobic reactions, ammonium is oxidized by nitrifying bacteria (nitrosomonas) to nitrite... 

A new concept is to use an on/oFf air supply cycle. During aeration, nitrates are produced. When the air is shut off, nitrates are reduced to nitrogen gas. This prevents acid buildup and removes nitrogen from the sludge. High power cost for aerobic digestion restricts the applica-bihty of this process. 

Initial carbon-nitrogen ratios (by mass) hetween 35 and 50 are optimum for aerobic composting. At lower ratios ammonia is given off Biological activity is also impeded at lower ratios. At higher ratios nitrogen maybe a limiting nutrient. 

As described in U.S, Patent 3,086,912, the process comprises cultivating Streptomyces lincolnensis var. lincolnensis in an aqueous nutrient medium containing a source of assimilable carbohydrate and assimilable nitrogen under aerobic conditions until substantial activity is imparted to the medium by production of lincolnensin and isolating the lincol-nensin so produced. 

The Fermentation Process The process by which this antifungal substance is produced is an aerobic fermentation of an aquaous nutrient medium inoculated with a pimaricin-producing strain of Streptomycesgihrosporeus. The nutrient medium contains an assimilable source of carbon such as starch, molasses, or glycerol, an assimilable source of nitrogen such as corn steep liquor and Inorganic cations such as potassium, sodium or calcium, and anions such as sulfate, phosphate or chloride. Trace elements such as boron, molybdenum or copper are supplied as needed in the form of impurities by the other constituents of the medium. 

A bacterium is grown aerobically with glucose as sole source of carbon and ammonium ions as nitrogen source. Experimental analysis shows that six moles of glucose are utilised for each mole of biomass produced. Write the reaction equation for growth if the elemental composition of the cells is CHi,666 CW Nojd. 

Figure 3.2 Theoretical relationships for (a) qs against dilution rate and for (b) Yp/S and Yx/s against dilution rate. The micro-organism is grown aerobically in a nitrogen limited chemostat culture.

Aim3 aerobic bioprocess was operated in a continuous mode with nitrogen as the growth limiting nutrient. The steady state biomass concentration (x), the biomass yield coefficient (Yx/S) and the product yield coefficient (Yp/t) were determined at a low and at a high dilution rate (D). 

Raw materials. Most luminous organisms can be stored at —70°C or below under aerobic conditions, or with dry ice, without a significant loss of luminescence activity for a period of several months or more, although a trial is always recommended. Even if a substance already extracted is unstable when stored with dry ice (like the luciferase of Cypridina and the luciferins of euphausiids and dinoflag-ellates), the same substance in the organisms before extraction can be safely stored at — 70° C or with dry ice. The material can also be stored with liquid nitrogen for added safety, but the quantity storable in a laboratory setup (e.g., Dewar flask) is limited. 

It is often taken for granted that the oxygen content of the air is nearly constant at ca. 20% of the atmospheric volume, that most of the liquid water on the planet is aerobic (i.e. contains O2), and that most water has pH values relatively close to neutral" (close to 7). However, these circumstances are not mere coincidences but are in fact consequences of the interaction of key global biogeochemical cycles. For instance, the pH of rainwater is often determined by the relative amounts of ammonia and sulfuric acid cycled through the atmosphere, a clear example of interaction between the nitrogen and sulfur cycles. 

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