Biodegradation of Petroleum Hydrocarbons

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ENVIRONMENTAL ENGINEERING SCIENCE Volume 21, Number 4, 2004 © Mary Ann Liebert, Inc. Biosurfactant Enhancement of Microbial Degradation of Various Structural Classes of Hydrocarbon in Mixed Waste Systems Suresh Inakollu,1 Huang-Chin Hung,2 and Gina S. Shreve2,* Matrix Inc. Detroit, MI 48202 2Department of Chemical Engineering and Materials Science Wayne State University Detroit, MI 48202 1Enviro ABSTRACT This study examines the effect of two rhamnolipid biosurfactants on the first-order biodegradation rate constant for a microbial consortium growing on a mixture of hydrocarbons representing four structural classes of hydrocarbons. The microbial biodegradation rate of hexadecane, dodecane, benzene, toluene, iso-octane, pristane (2,6,10,14 tetramethyl pentadecane), naphthalene, and phenanthrene in the presence and absence of a mixture of rhamnolipid biosurfactant was determined. A first-order biodegradation model was applied in these studies to better discern the differential solubilization and biodegradation rates for specific structural classes of hydrocarbons in hydrocarbon mixtures. The biodegradation rate was enhanced by the addition of biosurfactant levels above the critical micelle concentration for all hydrocarbon species except phenanthrene and naphthalene. The time required for complete removal of each of hydrocarbons from the culture was shortened due to the presence of surfactant, indicating a clear pattern in their order of removal based upon their structural class. The rhamnolipid biosurfactants enhanced the rate of linear alkane biodegradation more than the biodegradation rate of the monoaromatics. The rate constants for hexadecane and dodecane increased by 111 and 76% to 4.7 and 0.3 mg/h, respectively, while those of benzene and toluene increased by 34 and 65% to 3.1 and 4.0 mg/hr, respectively. The branched alkane degradation rate constants

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