MICROBIAL-DEGRADATION OF MARINE EVAPORITIC CRUDE OILS

The composition of alkylbenzenes and organosulphur compounds in crude oils is strongly modified by biodegradation, even at low levels of transformation where the composition of steranes, hopanes, alkylnaphthalenes, and alkylphenanthrenes has not been altered. These conclusions emerge from the comparison of preserved and biodegraded crude oils of marine evaporitic origin (Amposta and Varadero oils) and controlled experiments of microbial transformation of oils containing high amounts of aryl hydrocarbons and organic sulphur species. The compositions of straight chain compounds, such as n-alkanes, n-alkylbenzenes, 2,5-di-n-alkylthiolanes, 2,6,-di-n-alkylthianes and 2,4-dialkylbenzo[b]thiophenes are more easily modified than those of compounds with isoprenoid side-chains. The experiments also show that benzo[b]thiophenes are markedly more resistent to microbial than thiolanes and thianes.