An integrated treatment coupling ultrasonic and hydrothermal pretreatments with sequential alkali post-extractions was performed to isolate and characterize hemicelluloses from perennial ryegrass and improve the enzymatic hydrolysis efficiency of cellulose. The yield, chemical composition, and structure of water-soluble and alkali-soluble hemicelluloses obtained from the hydrothermal supernatant and hydrothermally pretreated ryegrass as well as the enzymatic hydrolysis efficiency of cellulose were comprehensively investigated by gel permeation chromatograph, high-performance anion exchange chromatography, Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectra. Results showed that more than 90 % of the original hemicelluloses in ryegrass were released during the integrated treatment and all hemicellulosic fractions obtained were mainly composed of ʟ-arabino-(4-O-methyl-ᴅ-glucurono)-ᴅ-xylans, galactoanrabinoxylans and β-glucans. In addition, the effective removal of amorphous hemicelluloses and lignin significantly increased the cellulose enzymatic hydrolysis rate of ryegrass from 43.8 to 91.1 %. These results provided new insights into the collaborative utilization of hemicelluloses and cellulose in ryegrass.
Keywords: Enzymatic hydrolysis; Hemicelluloses; Integrated treatment; Perennial ryegrass; Structural characterization.
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