title: Engineering soil organic matter quality: Biodiesel Co-Product (BCP) stimulates exudation of nitrogenous microbial biopolymers.
abstract: Biodiesel Co-Product (BCP) is a complex organic material formed during the transesterification of lipids. We investigated the effect of BCP on the extracellular microbial matrix or 'extracellular polymeric substance' (EPS) in soil which is suspected to be a highly influential fraction of soil organic matter (SOM). It was hypothesised that more N would be transferred to EPS in soil given BCP compared to soil given glycerol. An arable soil was amended with BCP produced from either 1) waste vegetable oils or 2) pure oilseed rape oil, and compared with soil amended with 99% pure glycerol; all were provided with15N labelled KNO3. We compared transfer of microbially assimilated15N into the extracellular amino acid pool, and measured concomitant production of exopolysaccharide. Following incubation, the15N enrichment of total hydrolysable amino acids (THAAs) indicated that intracellular anabolic products had incorporated the labelled N primarily as glutamine and glutamate. A greater proportion of the amino acids in EPS were found to contain15N than those in the THAA pool, indicating that the increase in EPS was comprised of bioproducts synthesised de novo. Moreover, BCP had increased the EPS production efficiency of the soil microbial community (μg EPS per unit ATP) up to approximately double that of glycerol, and caused transfer of 21% more15N from soil solution into EPS-amino acids. Given the suspected value of EPS in agricultural soils, the use of BCP to stimulate exudation is an interesting tool to consider in the theme of delivering sustainable intensification.
authors.affiliation: Dept. of Sustainable Soils and Grassland Systems, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK ; Organic Geochemistry Unit, Bristol Biogeochemistry Research Centre, School of Chemistry, University of Bristol, BS8 1TS, UK.
authors.forename: Marc A
authors.initials: MA
authors.lastname: Redmile-Gordon
authors.affiliation: Organic Geochemistry Unit, Bristol Biogeochemistry Research Centre, School of Chemistry, University of Bristol, BS8 1TS, UK.
authors.forename: Richard P
authors.initials: RP
authors.lastname: Evershed
authors.affiliation: Organic Geochemistry Unit, Bristol Biogeochemistry Research Centre, School of Chemistry, University of Bristol, BS8 1TS, UK.
authors.forename: Alison
authors.initials: A
authors.lastname: Kuhl
authors.affiliation: School of Energy, Environment and Agrifood, Building 52a, Cranfield University, Cranfield, Bedfordshire MK43 0AL, UK.
authors.forename: Elena
authors.initials: E
authors.lastname: Armenise
authors.affiliation: Dept. of Sustainable Soils and Grassland Systems, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK.
authors.forename: Rodger P
authors.initials: RP
authors.lastname: White
authors.affiliation: Dept. of Sustainable Soils and Grassland Systems, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK.
authors.forename: Penny R
authors.initials: PR
authors.lastname: Hirsch
authors.affiliation: Dept. of Sustainable Soils and Grassland Systems, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK.
authors.forename: Keith W T
authors.initials: KW
authors.lastname: Goulding
authors.affiliation: Dept. of Sustainable Soils and Grassland Systems, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK.
authors.forename: Philip C
authors.initials: PC
authors.lastname: Brookes
keywords: EPS matrix; Exocellular amino acids; Exopeptide; Exopolysaccharide; Extracellular polymeric substances; Glycerol; Nitrate; Protein dynamics