Biodegradation rate of diesel range n-alkanes by bacterial cultures Exiguobacterium aurantiacum and Burkholderia cepacia

The biodegradation rate of hydrocarbons is an important consideration determining the time scale for bioremediation in oil-contaminated environments. Two naturally occurring bacterial cultures, Exiguobacterium aurantiacum and Burkholderia cepacia, were capable of utilizing diesel oil as the sole source of carbon and energy by induction of hydrophobic cell surfaces with water contact angle greater than 70°. The cultures demonstrated good degradation characteristics for diesel range n-alkanes (C9–C26) and were also capable of degrading pristane. A significant correlation was observed between maximum decay rate (MTR) of individual n-alkane peak area and initial abundance of n-alkanes in diesel (r2=0.79 and 0.97 for E. aurantiacum and B. cepacia, respectively). Thus, MTR (day−1) was essentially constant, in the range of 0.07–0.20, for n-alkanes with a wide range of carbon numbers from C12 to C26. Biodegradation altered the relative abundance of n-alkanes in diesel and resulted in a loss of symmetry in n-alkane distribution. C9, C17–C19, and C26 were completely degraded by both the cultures. In B. cepacia, the residual diesel was enriched in the higher carbon number n-alkanes C20–C25. The MTR of n-C16 present as a component of diesel was comparable to that for n-C16 when present as sole substrate for B. cepacia but not for E. aurantiacum. Scientific relevance Two cultures E. aurantiacum and B. cepacia were capable of utilizing diesel oil as sole substrate and exhibited uniform decay rates for a wide range of n-alkanes from C12 to C26. In contrast, most researchers have reported decreasing degradation rate with increasing carbon number.