The use of high temperature gas chromatography to study the biodegradation of high molecular weight hydrocarbons

A consequence of the biodegradation of petroleum is that lower molecular weight compounds are removed preferentially to higher molecular weight (HMW) compounds greater than triacontane (n-C₃₀). The extent to which the latter compounds are biodegraded has rarely been studied. Reasons for this include the technical difficulties associated with carrying out biodegradability tests with solid, water-insoluble substances and the limits of the analytical techniques, such as gas chromatography (GC).A quantitative high temperature GC (HTGC) method was developed to monitor the biodegradation of the aliphatic fraction of a waxy Indonesian oil by Pseudomonas fluorescens. Recoveries of over 90% were obtained for n-alkanes up to hexacontane (C₆₀) using liquid-liquid continuous extraction. After only 14 days, 80% of the aliphatic hydrocarbons had been degraded. At the end of the 136-day study, 14% of the original fraction remained. This comprised mainly C₄₀₊ compounds. No decrease in the concentrations of compounds above C₄₅ was observed. However, the use of a rapid screening biodegradation method provided tentative proof that Pseudomonas fluorescens was capable of utilising n-alkanes up to C₆₀ once the bacteria had acclimated to HMW alkanes.