Hydrolysis Enhancement Of Highly Crystal Polysaccharides By Ultrasonic And Lonic Liquid Pretreatment

Structure analysis of polysaccharides is essentially important for exploring thestructure-activity relationship of polysaccharide and developing new functionalpolysaccharide. Acidic hydrolysis is the key step for polysaccharides structural analysis.However, acid hydrolysis is required for crystalline polysaccharides, but the strong acidconditions evidently lead to degradation of sugars. As crystal polysaccharides are of tightlypacked strucuture, high crystallinity and insoluble in water, degradative efficiencies forcrystalline polysaccharides are relativly low. In this study, acidic hydrolysis and mechanismof brewer’s yeast β-glucan,cordyceps polysaccharide and cardlan enhanced with ultrasonicand Ionic liquid1-butyl-3-methylimidazolium chloride ([BMIM]Cl) pretreatment werestudied by3,5-dinitrosalicylic acid assay (DNS), high performance anion-exchangechromatography with pulsed amperometric detection (HPAEC-PAD) and X-ray powderdiffraction. These results are indicated as following:1. The hydrolysis enhancement of crystal polysaccharides by ultrasounic pretreatment.The reducing sugar content and components analysis of crystal polysaccharides wereinvestigated by DNS assay and HPAEC-PADafter acidic hydrolysis, respectively. Resultsshowed that both the yields of reducing sugar and glucose were enhanced after ultrasounicpretreatment. Comparing to the untreated polysaccharides in4mol/L trifluoroacetic acid at100oC for4h, the yield of the reducing sugar with ultrasounic pretreatment (300w,20min)released from the regenerated brewer’s yeast β-glucan, cordyceps polysaccharide and cardlanis increased by20.8%,31.6%and26.2%, respectively. Meanwhile, the yield of glucose isincreased by21.8%,35.4%and35.6%, respectively, and maltose and maltotriose contents arelower than the untreated controlled polysaccharides.2. The hydrolysis enhancement of crystal polysaccharides by lonic liquid pretreatment.Results showed that when the mass fraction of crystal polysaccharides is5%, crystalpolysaccharides are dissolved well in [BMIM]Cl solvent at the temperature of100oC for2h.Both efficiencies of the acidic hydrolysis and components analysis of highly crystalpolysaccharides pretreated with [BMIM]Cl were investigated by DNS assay andHPAEC-PAD. It was showed that the yield of the reducing sugar with [BMIM]Clpretreatment released from the regenerated brewer’s yeast β-glucan, cordyceps polysaccharideand cardlan is increased by56.8%,44.0%and57.2%, respectively, than that of the untreatedsample in4mol/L trifluoroacetic acid at100oC for4h. Meanwhile, the yielding of glucose isincreased by44.6%,72.9%and75.2%than that of the untreated sample, respectively. The maltose and maltotriose content are lower than the untreated sample.3. The mechanisms of ultrasounic and ionic liquid pretreatment for promoting acidichydrolysis of highly crystal polysaccharides were investigated by X-ray powder diffraction,dynamic laser light scattering, FT-IR and differential scanning calorimetry. Results showedthat the ultrasounic and ionic liquid pretreatment may weaken the intra-molecular hydrogenbond in polysaccharide and reduce the crystallinity and aggregation state. These resultsshowed that the acid permeated in the structure of polysaccharide easily, indicating that theefficiency of acidic hydrolysis of crystalline polysaccharides can be enhanced.