The perfume of death - ambrein formation in human adipocere

• Applicant: Dr. Barbara von der Lühe
• Subject Area: Microbial Ecology and Applied Microbiology
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 432509546

Ambrein is the main constituent of ambergris and an important fixative chemical of perfumes. The marine derived ambergris is a rare faecal concretion (coprolith), occasionally found as jetsam on beaches or recovered from the intestines of Sperm whales (Physeter macrocephalus). In my preliminary work, I showed the first terrestrial detection of ambrein in human adipocere. Adipocere is a post-mortem concretion that is often formed from soft tissues in moist grave environments. However, no studies on natural ambrein formation in terrestrial and marine settings exist yet. In this project, I intent to close this knowledge gap by investigating the occurrence of ambrein in human adipocere and its biogeochemical linkage to ambergris. First observations revealed, that ambrein is always present (i) in waxy and fatty concretions, (ii) is associated with faecal and tissue-derived steroids and derivates thereof indicating an extensive microbial activity, (iii) is detected in moist and wet environments depleted in oxygen and, (iv) in aged material formed over several years. The main hypothesis of this project is that ambrein formation in terrestrial and marine settings arises from similar precursor molecules and -materials, and involves distinctive microorganisms and environmental conditions. Three objectives (O1-3) will be covered by three work packages (WP1-3) in order to test the project’s hypothesis. O1 & WP1 involves the characterisation and comparison of faecal and tissue steroids in adipocere with ambrein appearance. Higher ambrein concentrations are expected close to the intestines of the adipocere corpses with close association to faecal steroids and ambrein precursor molecules (e.g. squalene). O2 & WP2 intent to analyze non-steroid lipid biomarkers of post-mortem (adipocere) and post-excretion (ambergris) microbial activity. The supposed detection of microbial biomarkers (e.g. hopanoids, methyl-branched fatty acids) will allow to draw implications on the nature and extent of post-mortem and post-excretion microbial activity. In the third objective and work package, linkages between the microbial communities of adipocere and ambergris are determined that help in understanding the composition of bacterial inventories that might be responsible for ambrein formation in terrestrial settings. For all work packages, adipocere from anonymous grave exhumations with known ages and radiocarbon dated jetsam ambergris will be used. Lipids from adipocere and ambergris will be solvent-extracted and analysed, identified and quantified with gas chromatography-mass spectrometry (GC-MS), pyrolysis-GC-MS and compound specific 13C- and 2H-isotope analysis. Microbial communities of adipocere and ambergris materials will be characterized with DNA extraction and sequencing. The outcomes of this project will provide a detailed understanding of the biogeochemistry of ambrein formation in adipocere and ambergris.

• DFG Programme: Research Grants
• International Connection: United Kingdom
• Cooperation Partners: Professor Dr. Steven Rowland; Paul Sutton, Ph.D.