Variation in lignocellulose characteristics of 30 Indonesian sorghum (Sorghum bicolor) accessions

A comprehensive study on lignin contents and composition of 30 Indonesian sorghum accessions has been performed. Lignocellulose compositional analyses, i.e., thioglycolic acid assay, neutral sugar analysis, ash content measurement, and cell-wall-bound phenolic quantification, and lignin structural analyses, i.e., thioacidolysis and HSQC NMR analysis, of sorghum stem biomass were performed. In addition, their enzymatic saccharification efficiencies (ESEs) were also evaluated. The results showed that the total biomass was varied among accessions, ranging from 615.97 kg/plant (Pahat) and up to 1425.17 kg/plant (JP-1). Total lignin contents ranged from 14.35% to 22.89% of cell wall residues (CWRs), which were obtained from Pahat and KS, respectively. Analytical thioacidolysis and NMR analysis of selected 9 accessions with the lowest (Pahat, JP-1, and Buleleng Empok), moderate (Kawali, Super 1, and Super 2-300 Gy) and the highest (Sorgum Malai Mekar, 4183A, and KS) total lignin contents showed that lignin syringyl (S)/guaiacyl (G) unit ratio varied from around 0.8 to 1.5, where KS and 4183A had a relatively low and high S/G ratio, respectively. Correlation analysis of lignocellulose composition/structures with ESE showed significant associations of ESE with total lignin content, amorphous glucan content, and relative frequency of cinnamyl alcohol end-units in lignin polymers (P < 0.05, P < 0.01, P < 0.05, respectively). Taken together, this study provides a foundation toward further optimization of sorghum biomass composition for various biorefinery applications.