Determination of saprotrophic fungi turnover in different substrates by glucosamine-specific δ13C liquid chromatography/isotope ratio mass spectrometry

A high performance anion exchange chromatography (HPAEC) isotopic ratio mass spectrometry (IRMS) method was developed for amino sugar-specific δ13C analysis in plant hydrolysates. The HPAEC-IRMS method provided good validation parameters and the amino sugar concentrations were similar to those obtained by reversed phase (RP) high performance liquid chromatography (HPLC) and fluorescence (Fl) detection. The limit of quantification (LOQ) was 150 μmol l−1. This optimised HPAEC-IRMS method opens up the possibility of a glucosamine (GlcN) specific δ13C analysis in plant material. Thus, it was possible to determine the δ13C values in newly formed fungal GlcN for the first time. The formation and turnover of saprotrophic fungi was investigated by using the improved HPAEC-IRMS method for GlcN-specific δ13C analysis. The cultivation of saprotrophic fungi (Lentinula edodes and Pleurotus species) in beech wood mixed with maize or wheat straw showed the preferred formation of fungal biomass from maize-derived (80%) rather than from beech wood-derived C. The results indicate a faster formation of fungal biomass from maize than from wheat straw as co-substrate.

► A glucosamine-specific δ13C analysis by LC-IRMS was optimised.
► Glucosamine-specific δ13C in plant–fungi hydrolysates was successfully determined.
► The shifts in δ13C values were due to incorporation of maize-derived material.
► Almost no kinetic isotope fractionation was observed.