TY - JOUR
T1 - Generation of unusual branched long chain alkanes from hydrous pyrolysis of anammox bacterial biomass
AU - Rush, Darci
AU - Jaeschke, Andrea
AU - Geenevasen, Jan A J
AU - Tegelaar, Erik
AU - Pureveen, Jos
AU - Lewan, Michael D.
AU - Schouten, Stefan
AU - Sinninghe Damsté, Jaap S.
PY - 2014/11
Y1 - 2014/11
N2 - Anammox, the microbial anaerobic oxidation of NH4+ by NO2- to produce N2, is recognised as a key process in the marine, freshwater and soil N cycles, and has been found to be a major sink for fixed inorganic N in the ocean. Ladderane lipids are unique anammox bacterial membrane lipids used as biomarkers for such bacteria in recent and past environmental settings. However, their fate during diagenesis and early catagenesis is not well constrained. In this study, hydrous pyrolysis experiments were performed on anammox bacterial biomass and the generated aliphatic hydrocarbons, present in oil generated at 220-365°C, were analysed. A unique class of hydrocarbons was detected, and a representative component was isolated and rigorously identified using 2D nuclear magnetic resonance (NMR) spectroscopy. It consisted of C24 to C31 branched long chain alkanes with two internal ethyl and/or propyl substituents. The alkanes were generated above 260°C, with maximum generation at 320 and 335°C. Their stable carbon isotopic values were depleted in 13C, similar to carbon isotope values of the original anammox lipids, indicating that they were thermal products generated from lipids of anammox bacterial biomass. A range of sediments from different geological periods where anammox may have been an important process was screened for the presence of these compounds as possible catagenetic products. They were not detected, either because the concentration was too low, or the sediments screened were too immature for them to have been generated, or because the artificially produced products of anammox lipids may not reflect the natural diagenetic and catagenetic products of ladderane lipids.
AB - Anammox, the microbial anaerobic oxidation of NH4+ by NO2- to produce N2, is recognised as a key process in the marine, freshwater and soil N cycles, and has been found to be a major sink for fixed inorganic N in the ocean. Ladderane lipids are unique anammox bacterial membrane lipids used as biomarkers for such bacteria in recent and past environmental settings. However, their fate during diagenesis and early catagenesis is not well constrained. In this study, hydrous pyrolysis experiments were performed on anammox bacterial biomass and the generated aliphatic hydrocarbons, present in oil generated at 220-365°C, were analysed. A unique class of hydrocarbons was detected, and a representative component was isolated and rigorously identified using 2D nuclear magnetic resonance (NMR) spectroscopy. It consisted of C24 to C31 branched long chain alkanes with two internal ethyl and/or propyl substituents. The alkanes were generated above 260°C, with maximum generation at 320 and 335°C. Their stable carbon isotopic values were depleted in 13C, similar to carbon isotope values of the original anammox lipids, indicating that they were thermal products generated from lipids of anammox bacterial biomass. A range of sediments from different geological periods where anammox may have been an important process was screened for the presence of these compounds as possible catagenetic products. They were not detected, either because the concentration was too low, or the sediments screened were too immature for them to have been generated, or because the artificially produced products of anammox lipids may not reflect the natural diagenetic and catagenetic products of ladderane lipids.
KW - Anammox
KW - Branched long chain alkanes
KW - Hydrous pyrolysis
KW - Ladderane
KW - NMR
UR - http://www.scopus.com/inward/record.url?scp=84906492213&partnerID=8YFLogxK
U2 - 10.1016/j.orggeochem.2014.08.002
DO - 10.1016/j.orggeochem.2014.08.002
M3 - Article
AN - SCOPUS:84906492213
SN - 0146-6380
VL - 76
SP - 136
EP - 145
JO - Organic Geochemistry
JF - Organic Geochemistry
ER -