Aerobic biodegradation of hopanes and norhopanes in Venezuelan crude oils

The microbial degradation of two Venezuelan crude oils enriched in 25-norho panes was examined after a 5-week aerobic incubation using a microbial enri chment culture. Analysis of the oils using gas chromatography-mass spectrom etry revealed degradation of the C-28 tricyclic terpane, the C-29-C-34 17 a lpha (H),21 beta (H)-hopanes, and the C-29 17 alpha (H),21 beta (H)-25-norh opane, The C-35 17 alpha (H),21 beta (H)-hopane and 18 alpha (H)-oleanane w ere conserved. Further, the C-28-C-34 17 alpha (H),21 beta (H)-25-norhopane s were degraded and no formation of 25-norhopanes was observed. Degradation caused preferential removal of the 22R versus the 22S isomer in both the e xtended hopanes and 25-norhopanes, implying that bacteria remove these comp ounds in aerobic environments. These data demonstrate 25-norhopane degradat ion on a time scale similar to that for other biomarkers. (C) 2001 Elsevier Science Ltd. All rights reserved.