Production of Xylooligosaccharide, Nanolignin, and Nanocellulose through a Fractionation Strategy of Corncob for Biomass Valorization

The three-step fractionation strategy of corncob was performed for the efficient production of xylooligosaccharide, nanolignin, and nanocellulose. High yield of xylooligosaccharide (XOS) was produced from corncob through organic acid-NaOH pretreatment. The influences of the type and concentration of organic acids and the amount and time of NaOH added on the XOS yield were investigated. For resource efficiency, the pretreated corncob residue was further soaked in p-toluenesulfonic acid (p-TsOH) at 80 degrees C to extract lignin, and then the residue after secondary treatment was catalyzed by TEMPO to produce cellulose nanofibers. Results showed that 38.3% of XOS was achieved by formic acid-NaOH pretreatment, and the addition of NaOH at the later stage of the pretreatment process was proved to prevent the excessive hydrolysis of xylan, resulting in the selective depolylmerization of xylan during pretreatment. In addition, the atomic force microscopy (AFM) analysis showed that nanoscale lignin and cellulose were obtained by the subsequent treatment. TEMPO-oxidized cellulose remarkably swelled in water, and the nanocellulose paper with high transparency was successfully prepared.