Production of Xylooligosaccharides and Monosaccharides from Switchgrass by FeCl3 Hydrolysis Combined with Sodium Perborate Pretreatment

Abstract

The production of xylooligosaccharides (XOS) from lignocelluloses with a simple process and less chemical loading is challenging. Previously, some metal salts have been proven to depolymerize hemicellulose into xylose at low doses. However, few metal salts have been reported for the production of XOS from lignocelluloses. In this study, FeCl3 hydrolysis and FeCl2 hydrolysis of switchgrass were compared to produce XOS, then FeCl3-hydrolyzed switchgrass was delignified by sodium perborate (SPB) pretreatment for producing monosaccharides. The results showed that the highest XOS (DP 2-6) yield of 40.7% was obtained from switchgrass by 25 mM FeCl3 hydrolysis at 160 °C for 50 min. A high lignin removal (75.5%) and glucan retention (90.5%) of FeCl3-hydrolyzed switchgrass was obtained by 8% SPB pretreatment at 70 °C for 4 h. After cellulase (20 FPU/g dry mass) hydrolysis of SPB-pretreated switchgrass, 87.5% glucose, and 95.0% xylose were obtained. The results suggest that FeCl3 hydrolysis combined with SPB pretreatment is an efficient and novel method for producing XOS and monosaccharides from switchgrass under relatively mild conditions.Graphical Abstract