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BioOvr - Page 3 <br /> produces , bacteria commonly employ oxygenase enzymes (i . e. <br /> chemical compounds that catalyze the transfer of oxygen) . <br /> This transfer process requires the presence of molecular <br /> oxygen and its availability must be considered as an <br /> important limiting factor for petroleum degradation. When <br /> low to moderate concentrations of oil are thoroughly <br /> dispersed in aerobic water, it is unlikely that a lack of <br /> oxygen is a limiting factor. However, in cases where pools <br /> of oil accumulate in soils and sediments , in regions of <br /> intense decomposition, and in some groundwater, the <br /> development of anoxic conditions can severely limit the <br /> rate of (bio)degradation. <br /> Mineral Nutrients <br /> Petroleum is rich in carbon and energy, but deficient in <br /> those mineral nutrients necessary for microbial growth <br /> (primarily nitrogen, phosphorus, iron, and potassium) . <br /> Consequently, petroleum degrading microorganisms must <br /> obtain these essential materials elsewhere. Those projects <br /> in which macro- and micro-nutrients are carefully monitored <br /> and supplied appropriately have shown improved degradation <br /> rates . Nutrients are often supplied as a component of <br /> organic matter (such as compost) or as custom formulations <br /> of commercial fertilizers . <br /> Additional Factors <br /> In addition to the above, two interesting processes can, <br /> and probably most often do, occur in the degradation of <br /> petroleum hydrocarbons . These are sparing and co- <br /> oxidation. For example, acetate, an intermediate product <br /> in hydrocarbon biodegradation, has been found to reduce the <br /> utilization of hexadecane. The basis for this sparing <br /> effect is not well defined, but it certainly occurs for <br /> other hydrocarbons , as well . Co-oxidation is a process in <br /> which compounds which otherwise would not be degraded can <br /> be attached by enzymes due to the abilities of the <br /> individual microorganisms producing the enzymes to utilize <br /> other hydrocarbons within the petroleum mixture. The <br /> complexities of petroleum compounds provide an excellent <br /> chemical environment in which co-oxidation can occur, and <br /> many complex branched and cyclic hydrocarbons are degraded <br /> as a result . It has been found, for instance, that the <br /> degradation of hydrocarbons within a gasoline mixture <br /> occurred at a rate different from the degradation of <br /> individual compounds comprising the mixture. Phenomena <br /> such as these do not alter the metabolic pathways of <br /> degradation, but determine whether the enzymes necessary <br />