Optimizing yield and chemical compositions of dimethylsulfoxide-extracted birchwood xylan

Dimethylsulfoxide (DMSO) extraction is commonly used to study the chemical structures of original xylan in the plant cell wall, since the DMSO can preserve the original structure of the xylan as much as possible during the extracting process. In addition, the DMSO-extracted xylans have unique properties allowing their potential applications in emulsifying or filming materials. However, the yield of DMSO-extracted xylan is always low and the effects of different DMSO extraction conditions on the chemical compositions of xylan have not been fully studied, which greatly hinders its researches and applications. In this study, we have found that extensive delignification before DMSO extraction results in destruction of lignin-carbohydrate complex (LCC), leading to xylan yield and xylose unit content increased by up to 220% and 20%, respectively. Tert-butanol washing of the holocellulose can further increase the DMSO extracted xylan yield by ∼10%. The yield of xylan extracted by the DMSO at 80 °C for 7 h was obviously higher than that at room temperature for 3 d by 30%–40%. Thermal analysis showed that the xylans extracted at different conditions had thermal stability without obvious differences. The results indicate that the DMSO-extracted xylan with a high yield, a high purity and a high degree of acetylation can be extracted at a high delignification level, a high reaction temperature and a short reaction time. This study is of great significance for studying xylan structure-property relationships and promoting the applications of DMSO-extracted xylan.