Section: Graviton Rating:Output Summary: Draft Defense RRLReview of Related LiteratureI. BiodegradationBiodegradation is nature's way of recycling waste or breaking down organic matter into nutrients that can be used by other organisms (Environmental Inquiry, 2009). Accelerates the degradation of organic pollutants.A.1. Crude oilCrude oil contains environmentally harmful polycyclic aromatic hydrocarbons (PAHs). Crude oil is normally described as sweet (low sulfur) or sour (high sulfur) and light or heavy (depending on its density). Heavier oils can also be described as medium and bitumen. A light crude oil is generally one with an API (American Petroleum Institute) gravity of less than about 40. Brent crude, a major benchmark crude oil, has an API gravity of between 38 and 39. Heavy crudes will typically have an API gravity of 20 or less: The higher the API gravity, the lower the density. Sweet crude oil has a sulfur content of less than 0.5%, anything more is acidic. Heavy crude oil is more difficult to handle and is refined at higher costs to produce petroleum products such as gasoline, diesel, and aviation fuel (Pietersz, 2006-2009). Crude oil is classified into three groups based on the type of hydrocarbons it contains. Parrafin-based crude oil contains high molecular weight parrafins that are solid at room temperature, with little or no asphaltic (bituminous) matter producing highly lubricating oils. Asphalt-based crude oil contains large portions of asphaltic matter and little or no paraffin and is sensitive to temperature changes compared to paraffin-based crude oil. Mixed-base crude oil is the gray area between paraffin-based crude oil and asphaltic-based crude oil. Both paraffins and naphthenes are present......middle of paper......to the degradation of hydrocarbons in the aquatic environment. Nitrogen and phosphorus limit biodegradation in the soil. It is observed that there is no increase in biodegradation rates or an increase only after a delay of several months to a year when fertilizers are used. The rate of hydrocarbon metabolism decreases with increasing salinity in the range of 3.3 to 28.4% (Leahy and Colwell,1990).E.2. The use of PAHs by Mycobacterium vanbaalenii bacteria initiates degradation at three different sites: the K region (position 9,10), the Bay region (positions 1,2-, 3,4), the non-K or non Bay. It uses different enzymes which are the dioxygenases and monooxygenases of the hydroxylating ring. Initial ring cleavage is performed by the dioxygenase NidAB, large and small subunits that are encoded by the nidA and nidB genes, respectively. Dioxygenase activity is stereo- and region-specific.