Microbial Degradation of Diesel Fuel

Abstract

A mixed culture of microbes from soil was used to attempt to degrade diesel fuel. The microbes were added to Erlenmeyer flasks containing 100 ml of an aqueous, inorganic nutrient and 2 ml of #1 diesel fuel. These mixtures were stirred continuously by magnetic stirrers for periods of one to six days. Controls were used with diesel fuel and nutrient but no microbes. After the given periods of stirring were completed, the remaining diesel fuel was extracted with benzene. Then, the extract was analyzed by gas chromatography. About one-half of the diesel fuel was degraded in two days. The gas chromatograms show that the straight chain alkanes were degraded faster than other hydrocarbons. Spills of crude oil and its refined products in the oceans and domestic waters cause significant harm to the environment. Spills of oil will gradually break up due to wave action, evaporation, and microbial degradation. This study investigates the possibility of speeding up the natural break-up of oil by adding microbes capable of hydrocarbon degradation to the spill. Significant work in this area has been carried out by others. Chakrabarty (Anonymous, 1975; Cottrell, 1977) was able to fuse four existing strains of bacteria into one new strain capable of digesting two-thirds of the hydrocarbons found in crude oil. Soli and Bens (1972) found bacterial strains capable of digesting 50% of the crude oil in a synthetic sea water medium in 48 hours. Zajic and Supplisson (1972) showed that microorganisms selectively metabolize the n-paraffin fraction. Diesel fuel was chosen for use in this study rather than crude oil because the limiting temperature of the gas chromatograph column used would have made a study of crude oil degradation incomplete and impractical. In addition, spills of diesel fuel have occurred in rivers and streams. * This article is published as an example of a Junior Academy project. This content downloaded from 157.55.39.148 on Fri, 16 Dec 2016 07:40:05 UTC All use subject to http://about.jstor.org/terms VOLUME 85, NUMBER 2 73 Although most previous work in this field involved the use of pure strains of bacteria, a mixed culture of microbes from soil was chosen for this study because pure strains never exist in nature and, if introduced, will become contaminated.