Stable carbon isotope evidence for the microbial origin of C14-C18 n-alkanoic acids in soils

Eric Lichtfouse (1) , Gersende Berthier , Sabine Houot (2) , Enrique Barriuso (2) , Valerie Bergheaud (2) , Tatiana Vallaeys

1 ASD - Agronomy for Sustainable Development
2 EGC - Environnement et Grandes Cultures

In order to delineate the origin of soil fatty acids, crop soil samples have been incubated for 21 days in vitro either with unlabelled or 13C-labelled glucose. Analyses of C14-C32 n-alkanoic acids from monocarboxylic acid fractions, as methyl esters, by gas chromatography-combustion-isotope ratio monitoring mass spectrometry (GC-C-IRMS) show that C14, C16 and C18 n-alkanoic acids are 13C-labelled, thus demonstrating their derivation from soil microorganisms, e.g. fungi or bacteria, growing during the experiment. Higher n-alkanoic acids, C16-C33 n-alkanes, and C22-C30 n-alkanols have not been significantly labelled, thus suggesting their derivation from other sources, e.g. higher plants. This short-term tracer experiment using stable carbon isotopes represents a novel and fruitful approach to study organic matter transformations in soils and other systems such as sediments.

Mots clés: 13C; soil fatty lipids; n-alkanes in soils; n-alkanols in soils; n-alkanoic acids in soils; microbial acids; soil organic matter

Domaines: Science des sols; Chimie analytique; Géochimie

Eric Lichtfouse, Gersende Berthier, Sabine Houot, Enrique Barriuso, Valerie Bergheaud, et al.. Stable carbon isotope evidence for the microbial origin of C14-C18 n-alkanoic acids in soils. Organic Geochemistry, 1995, 23 (9), pp.849-852. ⟨10.1016/0146-6380(95)80006-D⟩. ⟨hal-00192937⟩