Controlled conversion of sodium hyaluronate into low-molecular-weight polymers without additives using high-temperature water and fast-heating-rates

In this work, molecular weight reduction of the polysaccharide biopolymer, sodium hyaluronate (NaHA), was obtained without added chemicals or catalysts using high temperature water (180 to 260) degrees C, fastheating-rates (417 to 750) degrees C.s(-1) and short reaction times (< 18s) in a flow reactor. Results show that hydrothermal treatment of NaHA with fast-heating-rates convert the substrate into low molecular weight oligomers with minimal byproduct formation. A kinetic model assuming random depolymerization provided data correlation and allowed estimation of molecular weight reductions. Mechanism of NaHA decomposition in high temperature water with fast-heating rates seems to be related to initial disentanglement of NaHA random coils through convective (turbulent) mixing and shear that minimizes heterogenous decomposition. Evidence for the mechanism includes lack of significant furan byproducts (fast-heating), clear product solutions and model applicability. Fast-heating with high temperature water allows selective conversion of high molecular weight NaHA into low molecular weight HA fragments without chemical modification, catalysts or additives. (C) 2019 Elsevier B.V. All rights reserved.