The Structural Changes Of Cell Wall Skeleton Components During The Isolation Of Polysaccharide From Chinese Quince Fruits

Chinese quince（Chaenomeles sinensis）belongs to the papaya genus of Rosaceae.The fruit is rich in phenols,organic acids and lignin,showing a sour and hard taste,so it is difficult to be eaten directly.Pectin,cellulose,hemicellulose polysaccharides and lignin components constitute the skeleton of plant cell walls.These cell polysaccharides are rich in Chinese quince,and can be widely used in food,medicine,construction and other fields.However,the current raw materials for of the production of cell wall polysaccharides are still insufficient.Therefore,extracting cell wall polysaccharides from Chinese quince will effectively alleviate the domestic demand for polysaccharides and improve the industrial value of processing chain of Chinese quince.Compared with other non-lignin materials,these polysaccharides in Chinese quince of cell wall skeleton crosslinked with lignin to form a lignin-carbohydrate complex（LCC）with complex structure.The existence of this structure is an important mechanism that seriously restricts the dissolution of polysaccharides from cell wall.Therefore,it is necessary to interpret the cell wall skeleton,especially the structure of LCC,which is very important to obtain the information of the isolation mechanism of cell wall polysaccharides.The main research contents and conclusions of this report are as follows:1.The structural changes of lignin during the sequential of pectin and hemicellulose in Chinese quince:The yield of lignin components was improved,and the thermal stability and molecular weight were also changed after sequential of pectin and hemicellulose.Arabinose,galactose and glucose were the main monosaccharides remaining in the five lignin samples,and the increase of aliphatic OH content is related to arabinose.The main linkages between lignin units wereβ-O-4′aryl ether bond,and during the removal of pectin and hemicellulose,β-O-4′aryl ether bond will produce polymerization.The above results provide a theoretical basis for the later study of the structural interpretation of LCC in the process of pectin and hemicellulose fractionation.2.The structural changes of LCC（Bj（?）rkman LCC and LCC-Ac OH）during the sequential of pectin and hemicellulose in Chinese quince:Galactose-lignin complex and glucose-lignin complex were the main linkages between polysaccharides and lignin in Bj（?）rkman LCC after the fractional separation of pectin and hemicellulose,while arabinose-lignin complex is the main linkages between polysaccharides and lignin in LCC-Ac OH.The LCC linkages in Bjorkman LCC were mainly phenyl glycosides,and the LCC linkages in LCC-Ac OH were mainlyγ-ester linkages,and CDTA and alkaline reagents can promote the dissolution of pectin and hemicellulose polysaccharides by destroyingγ-ester linkages in LCC.In addition,the S/G ratio of LCC-Ac OH component increased,and a large amount of S-type lignin was released,especially in the LA₅ component.Chemical linkages in the LCC can be broken by removing S-type lignin from the cell wall.These results reveal the mechanism of the dissolution of pectin and hemicellulose polysaccharides in LCC.3.The structural changes of LCC from Chinese quince during enzymatic hydrolysis of cell wall polysaccharides:The contents of arabinose and total sugar in PBL and CXPBL fractions were reduced after pectinase treatment,which indicated that pectinase could break the strong linkages between arabinose and lignin in LCC,so as to promote the dissolution of pectin polysaccharides.After xylanase enzymatic hydrolysis,XBL and XLA fractions have the worst thermal stability.It can be considered to reduce the thermal properties of these two components to weaken the bonding strength of hemicellulose and lignin in LCC to promote the dissolution of hemicellulose.In the process of cellulase and xylanase fractionation,β-O-4’bond polymerization occurred,which promoted the release of more G-type lignin.A large amount of S-type lignin could be removed from the secondary layer S2 by cellulase hydrolysis,so as to effectively improving the dissolution rate of cellulose polysaccharide in Chinese quince.These results further explain the bonding relationship between cell wall polysaccharides and lignin in LCC structure,and provide a theoretical basis for the dissolution mechanism of cell wall polysaccharide in enzymatic hydrolysis of LCC.4.Based on the structural changes of LCC cleavage components after high-pressure hydrothermal treatment of Chinese quince:High temperature and high pressure can break the glycosidic linkages in LCC to dissolve the cell wall polysaccharide and lignin,but in the process of dissolution,some cell wall polysaccharides will degrade and contain a large number of amorphous regions,and the lignin fragments will form polymers with high molecular weight.The RSD-1,RSD-2 and RSD-3 fragments dissolved by LCC under high temperature and high pressure at 200℃have high thermal stability.The glycosidic linkages between galacturonic acid in pectin polysaccharide in the form of LCC is mainly 4→)-α-D-Gal Ap-(1→.These results elucidate the dissociation mechanism of LCC structure in Chinese quince based on high-pressure hydrothermal method,so as to provide a theoretical reference for the process mechanism of extracting cell wall polysaccharides from Chinese quince by high-pressure hydrothermal method.In the study of this subject,it can be understood that the strong linkages mode of LCC from Chinese quince is mainly arabinose-lignin complex,which can be broken by cellulase.High temperature and high pressure conditions can destroy the glycosidic bonds in LCC,so as to promote the dissolution of cell wall polysaccharides.This paper reports the dissolution mode of polysaccharides in the cell wall skeleton of Chinese quince,in order to realize the potential application value of smooth skinned papaya fruit.