Improving the extraction efficiency of sedimentary carbohydrates by sequential hydrolysis

摘要

Carbohydrates serve as structural materials, energy storage compounds, and energy carriers in organisms and provide insights into the dominant sources and the degradation state of organic matter (OM). Several studies have analyzed dissolved and/or particulate carbohydrates in the environment, often with the aim of studying particular carbohydrate groups of interest. These studies have often employed different acids and hydrolytic conditions, making comparisons across studies a challenge. Here, we introduce a sequential acid hydrolysis protocol for the comprehensive extraction, quantification and compositional investigation of carbohydrates in sediment samples. This protocol has four acid hydrolysis steps that sequentially increase in extraction strength, where each subsequent hydrolysis step is performed on the unextracted remains previously hydrolyzed. The four hydrolysis steps consist of 1 M HCl for 2 h at (1) room temperature, (2) 50 degrees C, and (3) 105 degrees C, followed by incubation for 8 h using (4) 6 M HCl and 105 degrees C. Based on tests using diverse carbohydrate standard compounds, the protocol recovers most diand oligosaccharides and soluble polysaccharides during the initial hydrolysis steps, whereas the recovery of most insoluble polysaccharides is highest during the final extraction step. Applying this protocol to different sediment types shows that recoveries of neutral sugars, amino sugars and sugar alcohols are on average similar to 60% higher than with a reference one-step extraction method using only hydrolysis with hot 6 M HC1. This sequential extraction protocol thus provides an important new tool for the quantitative and compositional analysis of carbohydrates in aquatic sediments. (C) 2020 Elsevier Ltd. All rights reserved.