Changing the ratio of phenolic compounds to saccharides is an approach to the regulation of antioxidant properties of polysaccharides

Abstract

Rice straw is an agricultural waste rich in lignocellulose. Soluble polysaccharides (SPs) and phenolic compounds are released from rice straw during bioethanol production. In this study, the composition of the SPs was analyzed using HPLC. It was found that phenolic compounds were another major component in the SPs besides saccharides. FT-IR of the SPs indicates that the phenolic compounds were covalently linked to the SPs in the form of ester or ether bonds. GPC analysis showed that the ratio of phenolic compounds to saccharides (P/S) was related to the molecular weight. The SPs with higher P/S exhibit stronger antioxidant capacities. The relationships between the molecular weight, P/S, and antioxidant capacity were identified by regulating the P/S of the SPs using a laccase oxidation method. The results indicate that the oligosaccharides in the SPs have a higher P/S and were the major contributor to the antioxidant capacity. The SPs derived from rice straw exhibit much higher antioxidant capacities than commercial SPs, suggesting that lignocellulosic biomass is a suitable material for the preparation of SPs with high antioxidant properties.