Le bilan du carbone dans une experience de biodegradation bacterienne d'un petrole brut

The relative part of the different forms of the carbon constituting the hydrocarbons in an in vitro topped crude oil biodegradation experiment by soil bacteria, in 21 days at 25°C, was determined. The abiotic loss (evaporation) was estimated to be 20% of the initial carbon and the global biodegradation, comprising total and primary biodegradation, reached 21%. The total biodegradation included the carbon transformation into CO₂ (mineralisation) and into biomass, estimated respectively at 13·7 and 5·6% of the initial carbon. The primary biodegradation, as measured by the organic carbon dissolved in the medium, represented 1·5% of the initial carbon. Another estimation of the global biodegradation, independently obtained by the residual weight of the chloroform extract, gave a similar result (22%). An analysis of the chloroform-extracted residue, performed by column fractionation and gas-liquid chromatography, showed that the saturate fraction was 40% degraded and the aromatic fraction, 18%. The pristane and phytane were completely biodegraded and no increase of long chain paraffins was noted. A statistically highly significant absolute increase of the asphaltic fraction, due to accumulation of extracellular products, was shown.