Effect of ultrasonic time on the structural and physico-chemical properties of hemicelluloses from Eucalyptus grandis.

Effect of sonication on the extractability and physico-chemical properties of hemicelluloses from Eucalyptus grandis using 5% KOH solution at 50 °C for 3 h has been comparatively studied. The results showed that the yield of hemicelluloses increased from 2.6 to 19.6% as the ultrasonic time was extended from 5 to 35 min. The highest yield of hemicelluloses (95.2%) was achieved at 30 min ultrasonic time. Xylose was the dominant sugar (82.94-84.96%) of all the hemicellulosic fractions. Furthermore, the hemicelluloses obtained by ultrasound-assisted extractions had slightly lower molecular weights (74,510-66,770 g/mol) and thermal stabilities, but higher contents of xylose (83.95-84.96%). The increased yield of ultrasonically extracted hemicelluloses, which have preserved their main structural properties, confirmed the great potential of ultrasound-assisted extraction to separate hemicelluloses from Eucalyptus grandis at an industrial level.