Production of xylooligosaccharides and monosaccharides from switchgrass by FeCl3 hydrolysis combined with sodium perborate pretreatment

Abstract

Abstract The production of xylooligosaccharides (XOS) using metal salt-catalyzed hydrolysis has the advantages of rapid reaction and mild conditions. At present, no metal salt has been reported that can be used to produce XOS from switchgrass. In this study, the productions of XOS from switchgrass using the hydrolysis of FeCl3 and that of FeCl2 were compared with each other, and the residual lignin in FeCl3-hydrolyzed switchgrass was removed using sodium perborate (SPB) for producing monosaccharides. The highest XOS (X2-X6) of 40.7% was obtained from switchgrass using the hydrolysis of 25 mM FeCl3 at 160°C for 50 min. The optimized conditions for the SPB pretreatment of FeCl3-hydrolyzed switchgrass were 8% (w/v) SPB, 70°C, and 4 h, which removed 75.5% of lignin and retained 90.5% of glucan. After the hydrolysis of switchgrass’s solid residue using cellulase, 87.5% glucose and 95.0% xylose were obtained. The results suggest that the hydrolysis of FeCl3 combined with SPB pretreatment is an efficient novel method for producing XOS and monosaccharides from switchgrass under relatively mild conditions.