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Extraction and enzymatic assay of glucose in soils with divergent pH, clay and organic carbon contents

Liang, Zhi; Olesen, Jørgen E.; Nørgaard, Trine and Elsgaard, Lars (2020) Extraction and enzymatic assay of glucose in soils with divergent pH, clay and organic carbon contents. Communications in Soil Science and Plant Analysis, 51 (3), pp. 380-391.

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Glucose (C6H12O6) is common in soils and widely used as a model substrate to trace the turnover of dissolved organic carbon. Yet, challenges and limitations of extraction and direct quantification of glucose in divergent soils are poorly documented. Here we used a simplified procedure for extraction and enzymatic glucose quantification with 18 soils representing different pH, clay and organic carbon (OC) contents. Extracts were reacted for 30 min (20°C) with glucose oxidase, peroxidase, and o-dianisidine. The reaction was terminated with H2SO4 and oxidized o dianisidine was measured spectrophotometrically (540 nm). Recovery of glucose from mineral soils was not significantly affected by soil pH and OC, but decreased to 96% for increasing clay contents (up to 45% clay). Extraction of soil in water (1:5, w/v) for 0.5 min was sufficient for sandy soils, whereas clayey soils were extracted for 5 min with benzoic acid (0.1%, w/v) as antimicrobial agent. Assays with organic soils (20% and 29% OC) showed that enzymatic glucose quantification was impeded presumably by extractable humic substances. It was possible to address this limitation with matrix-matched standard curves, but results from organic soils should be interpreted with care. The procedure had a detection limit of ~1.5 μg g−1 soil and was applicable to small (1 g) soil samples allowing to trace the recovery and dynamics of glucose in time-course experiments. The procedure could also be applied to native soil samples in which case references for colorimetric background are prepared by adding H2SO4 to the soil extract prior to the addition of assay reagents.

EPrint Type:Journal paper
Keywords:Glucose extraction; glucose quantification; enzymatic assay; clay; organic soils
Subjects: Soil > Soil quality > Soil biology
Research affiliation: Denmark > Private funders/foundations > Deep Frontier
Deposited By: Liang, Zhi
ID Code:37962
Deposited On:11 May 2020 10:48
Last Modified:11 May 2020 10:48
Document Language:English
Refereed:Peer-reviewed and accepted

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