Abstract

Understanding the amount of cellulose present on the deep-sea floor is a major challenge in studying deep-sea ecosystems. However, conventional sugar analysis methods cannot directly address this question. Here, we propose a novel quantification methodology based on extraction with a heavy liquid followed by selective enzymatic hydrolysis. First, sediment samples undergo acid and alkaline pretreatment. Then, extraction is performed using density separation with a heavy liquid. The extracts contain not only cellulose but also minor amounts of light inorganic matter. Therefore, the extracts are further subjected to the selective hydrolysis by cellulase and β-glucosidase. During enzymatic hydrolysis, cellulose is converted into glucose, which is quantified using a commercial glucose assay kit. From the measured glucose content, the cellulose concentration in benthic sediment samples can be determined. While this method successfully quantified 1 mg of artificially added cellulose in 200 mg of spiked model deep-sea sediment, no native sediment samples have yet exhibited cellulose concentrations above the detection limit.