Production of Hemicellulose Sugars Combined with the Alkaline Extraction Lignin Increased the Hydro-Depolymerization of Cellulose from Corn Cob

Hydro-depolymerization is a novel method for converting agricultural waste into eco-friendly and promising products. Due to the complex structure and composition of corn cob (CC), a three-step process was developed, which involved pre-hydro-depolymerization of hemicellulose, alkaline extraction of lignin, and hydro-depolymerization of cellulose. The pre-hydro-depolymerization step was at first optimized to produce five-carbon and six-carbon sugars, achieving a maximum hemicellulose conversion rate of 78.48 ± 3.92%, and reducing a sugar yield of 59.12 ± 2.95%. Alkaline treatment achieved a maximum lignin extraction efficiency of 73.76 ± 3.68%. After hemicellulose removal and delignification, the cellulose conversion rate increased to 36.63% and further increased to 76.97% after five cycles. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were performed to confirm physical and chemical changes in CC residues. The integrated process of hydro-depolymerization and alkaline treatment enables the complete exploitation of cellulose, hemicellulose, and lignin, and thus holds great potential for application in the agriculture industry.