Biodegradation of Hopane Prevents Use as Conservative Biomarker During Bioremediation of PAHs in Petroleum Contaminated Soils

The pentacyclic triterpane C₃₀ 17α (H), 21β (H)-hopane, a biomarker commonly used in hydrocarbon bioremediation laboratory experiments and field studies, was found to be completely removed without the formation of the demethylated intermediate nor-hopane in a crude oil-contaminated soil undergoing slurry biotreatment, while PAHs such as benzo(e)pyrene were recalcitrant. The partial or complete biodegradation of hopane has also been previously reported in a few bioremediation studies and has been explored by petroleum geochemists in an effort to characterize crude oil deposits. It is currently not clear what conditions induce hopane biodegradation or biotransformation, although the use of microbial enrichment cultures appears to speed up the process. Considering that hopane is not necessarily conserved during a bioremediation study, the uncritical normalization of hydrocarbon concentrations using this biomarker can lead to incorrect estimates of biodegradation rates and extents. If hopane is found to be unstable in a particular case, other potential biomarkers such as pentahopane, oleanane, or vanadium may be used instead.