The Degradation of Octane in Continuous Culture

Abstract

The purpose of this study is to use the technique of continuous culture to study the microbial degradation of oil in aquatic environments. Although much work has been done in the field of biodegradation of oil and hydrocarbons, very little of this work has used continuous culture techniques. The continuous system is an open system which will provide a condition more similar to the natural environment. It is the hope that the mechanisms of oil breakdown by bacteria in nature will be more understandable by the use of this technique. In this study a normal alkane, octane, was chosen as the principle substrate to test the feasibility of the continuous culture approach. The reason octane was chosen was because: a) it is very slightly soluble in water b) its mechanism of degradation is known c) it is available in chemically pure form and d) it is relatively non-volatile. Using mixed population and pure culture studies, we hoped to gain insight into how fast bacteria degrade hydrocarbons, to what degree the degradation rate is affected by environmental factors and whether the mixed populations of bacteria compete with each other during the degradation process. Since hydrocarbons are poorly soluble in water, it has been thought that the hydrocarbons must be mechanically dispersed in the water phase in order to get microbial degradation. However, these dispersion techniques are difficult to incorporate into continuous culture systems. For example, large amounts of hydrocarbon are required, the amount of hydrocarbon dispersed must be constant with time and rubber tubing is required which will not be affected by the hydrocarbons. To circumvent these problems, a continuous culture system was designed in which the hydrocarbon is floated on the surface of a water column under conditions in which it was not dispersed. The purpose of such a device was to show in fact that the hydrocarbon could be degraded in this type of continuous culture system and to demonstrate the factors that affect the degradation process.