An integrated biorefining approach was implemented to refine the hemicellulose, cellulose, and lignin polymers from sorghum stover, the best-suited crop for semi-arid regions, and the sequential extraction procedure was optimized to maximize biopolymer yield while minimizing feedstock waste. First, the extractives rich in 3-deoxyanthocyanins (2% w/w of biomass), proteins (7% w/w), and monosaccharides (12% w/w) were extracted via accelerated solvent extraction with 51% aqueous, acidified ethanol at 50 °C. Next, the extractives-free biomass was subjected to hydrothermal fractionation (170 °C, 30 min, 10% w/v loading) to isolate the hemicellulosic oligosaccharides (18% w/w yield). The resulting liquid fraction enriched in xylooligosaccharides (44%) was fed to pre-weaned dairy calves (7 to 21 days old) as a dietary supplement. Exhaustive transcriptomics profiling of the dairy calves’ hindgut epithelia was conducted to determine the anti-inflammatory mechanism and shifts in gut microbiome proffered by the sorghum stover xylooligosaccharides.
In the final step, hydrothermally treated solid residues were subjected to organosolv fractionation (butanol, water, 0.05% acetic acid), where six pulping conditions were tested (140, 160, 180 °C and 15, 30, 60 min) and optimized to maximize the yield of lignin (18% w/w) and cellulose (33% w/w). The cellulose fractions with varying amount of lignin were spun using the Lyocell process and the resulting fibers were tested for their resistance to water and oil. Presence of organosolv lignin residues significantly improved the water resistance as well as oil absorption of these fibers, thereby demonstrating their potential application in oil-water separation. Overall, the sequential fractionation process facilitated the use of ≥90% of sorghum stover in diverse value-added products. Such systems-based approach is essential to improve the profit margin as well as the sustainability of the biorefining industry.
