Fractional Separation and Structural Characterization of Chlorophyll and Lignin from Perennial Ryegrass (L. perenne) and Cocksfoot Grass (D. glomerata)

Effect of integrated treatment on enhancing the enzymatic hydrolysis of cocksfoot grass and the structural characteristics of co-produced hemicelluloses

BACKGROUND

Cocksfoot grass (Dactylis glomerata L.) with high biomass yield and rich cellulose can be used to produce bioethanol as fuel additive. In view of this, ultrasonic and hydrothermal pretreatments followed by successive alkali extractions were assembled into an integrated biorefinery process applied on cocksfoot grass to improve its enzymatic hydrolysis. In this work, the effects of ultrasonic and hydrothermal pretreatments followed by sequential alkali extractions on the enzymatic hydrolysis of cocksfoot grass were investigated. In addition, since large amount of hemicelluloses were released during the hydrothermal pretreatment and alkali extraction process, the yields, structural characteristics and differentials of water- and alkali-soluble hemicellulosic fractions isolated from different treatments were also comparatively explored.

RESULTS

The integrated treatment significantly removed amorphous hemicelluloses and lignin, resulting in increased crystallinity of the treated residues. A maximum saccharification rate of 95.1% was obtained from the cellulose-rich substrate after the integrated treatment. In addition, the considerable hemicelluloses (31.4% water-soluble hemicelluloses and 53.4% alkali-soluble hemicelluloses) were isolated during the integrated treatment. The released water-soluble hemicellulosic fractions were found to be more branched as compared with the alkali-soluble hemicellulosic fractions and all hemicellulosic fractions were mixed polysaccharides mainly composed of branched xylans and β-glucans.

CONCLUSION

The combination of ultrasonic and hydrothermal pretreatments followed by successive alkali extractions can dramatically increase the enzymatic saccharification rate of the substrates and produce considerable amounts of hemicelluloses. Detailed information about the enzymatic hydrolysis rates of the treated substrates and the structural characteristics of the co-produced hemicelluloses will help the synergistic utilization of cellulose and hemicellulose in cocksfoot grass.

Preparation of Cellulose Succinates with High Degree of Substitution in Solvent System [C4mim]Cl/DMSO

Homogeneous derivatization of cellulose was investigated with succinic anhydride (SA) in a solvent system containing 1-butyl-3-methylimidazolium chloride ionic liquid ([C4mim]Cl) and dimethylsulfoxide (DMSO) using iodine, N-bromosuccinimide (NBS), and 4-dimethylaminopyridine (DMAP) as a catalyst. The results showed that the high degree of substitution (DS) of modified cellulose significantly increased from 0.24 without any catalysts to 0.84, 2.31, and 2.34 under same conditions except with I2, NBS, and DMAP, respectively, as a catalyst. The possible mechanism of succinoylation catalysed with different catalysts was discussed. Fourier transform infrared and solid-state cross-polarization/magic angle spinning 13C NMR spectroscopies also provided evidences of catalyzed homogeneous succinoylation reaction. The results indicated that iodine, NBS, and DMAP could effectively improve the succinoylation efficiency of cellulose in [C4mim]Cl/DMSO.