Section: Graviton Evaluation: Result Summary: Draft RRL for DefenseReview 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). It accelerates the degradation of organic pollutants.A.1. Crude OilCrude oil contains polycyclic aromatic hydrocarbons (PAHs) which are harmful to the environment. Crude oil is normally described as sweet (low sulfur) or sour (high sulfur) and light or heavy (depending on its density). Heavier oils may also be referred to as medium oils and bitumen. A light crude oil generally has an API (American Petroleum Institute) gravity below about 40. Brent crude, an important benchmark crude, has an API gravity of 38 to 39. Heavy crudes will generally 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 above that is acidic. Heavy crude is more difficult to handle and is refined at higher cost 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. Paraffin-based crude oil contains high molecular weight paraffins that are solid at room temperature, with little or no asphaltic (bituminous) material producing highly lubricating oils. Asphalt-based crude oil contains large portions of asphaltic material and little or no paraffin and is sensitive to temperature changes than paraffin-based crude oil. Mixed-base crude oil is the gray area between paraffin-based crude oil and asphalt-based crude oil. Paraffins and naphenes are present ...... middle of paper ...... in 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 period of several months to a year when fertilizers are used. Rates of hydrocarbon metabolism decrease with increasing salinity, in the range of 3.3 to 28.4% (Leahy and Colwell, 1990).E.2. The use of PAHs by the bacterium Mycobacterium vanbaalenii initiates degradation at three different sites: the K region (position 9,10), the Bay region (position 1,2-,3,4), the non-K or non-Bay region. . It uses different enzymes which are the hydroxylating dioxygenases and monooxygenases of the cycle. Initial cleavage of the ring is carried out by NidAB dioxygenase, large and small subunits encoded by the nidA and nidB genes, respectively. Dioxygenase activity is stereo and region specific.