Study On Chemical Composites And Degradation Of Parenchymal Tissue In Bamboo

Bamboo resources are widely used in the area of artificial board, pulping and paper-making and natural bamboo fiber so far. However, few studies focus on bamboo classification and high-value utilization of bamboo, which limite the comprehensive utilization of the values of bamboo resources. In this paper, parenchymal tissues were separated from moso bamboos, relevant physical and chemical properties of parenchymal tissues were studied and the chemical components were analyzed and characterized.The main component, hemicellulose in the parenchymal tissues, was degraded by hemicellulase. The operation conditions of using hemicellulase to degrade hemicellulose was optimized and the enzymatic hydrolysate were analyzed as well. The main research contents and results of this paper are as follows:In order to explore the differences in chemical composition contents of parenchymal tissues and vascular bundles, the method of physical and mechanical and manual separation was used for separating parenchymal tissues and vascular bundles from bamboo. The composition contents were measured by corresponding methods. It turns out that the differences of ash and lignin contents between these two tissues were not apparent, and they were at a level of 1% and 20% respectively. Benzene-ethanol extract of parenchymal tissues was at a level of 10.7% which is about twice of that in vascular bundles. The content of hemicellulose in parenchymal tissues was about 46.74%, much higher than 28.53% in vascular bundles. The main components of parenchymal tissues was hemicellulose and the vascular bundles was cellulose.In order to explore the differences in physical and chemical properties of parenchymal tissues and vascular bundles, SEM, TG, XRD were used to characterize morphology features, hygroscopicities, heat stabilities and crystallinities of the two separated tissues correspondingly. SEM graphs showed that parenchymal tissues were with a shape of square cell and a loose and friable texture while vascular bundles are like fiber bundles and packed closely. Analysis of TG and thermal decomposition kinetics indicated that vascular bundles had a better heat stability and needed more activation energy when in the pyrolysis. XRD results showed that vascular bundles has a higher relative crystallinity of 7.8% than parenchymal tissues.In order to explore the specific chemical components and architecture features of parenchymal tissues, extracts, lignin, hemicellulose and cellulose were separated from parenchymal tissues. The chemical components and structure were analyzed and characterized by using instruments like GC-MS, UV, FTIR, GC, XRD correspondingly. Analysis of GC-MS showed that the main chemical components of the extracts are esters, ketones and alcohols. Characterization of UV and FTIR says indicated that there is a large amount of guaiacyl units and syringyl units in lignin. Analysis of FTIR and GC suggested that hemicellulose is mainly constituted of xylan which backbone is linked by (1�'4)β glycosidic linkage of xylosylation. Monosaccharides were mainly consisted of xylose, glucose and arabinose. The cellulose was extracted from parenchymal tissues and vascular bundles, and their molecule weight measured by viscometric method showed that the viscosity average molecular weight of cellulose in parenchymal tissues was smaller than that in vascular bundles at about 4.0×104. And the result of XRD suggested that crystallinity of cellulose in vascular bundles was higher than that in parenchymal tissues, the increse of crystallinity could be attributed to the increase of molecular weight of cellulose.The main components of parenchymal tissue, hemicellulose, was degraded by hemicellulase. The optimal conditions of hemicellulase degrading hemicellulose was studied and the degradational processes was optimized by the method of response surface. The main components of enzymatic hydrolysates was analysed by high-performance liquid chromatography. The results showed that, hemicellulase has the greatest activity under the condition of PH=4.8 with a temperature of 48 ℃. Based on the single factors of enzymolysis, by method of response surface and considered all factors comprehensively and drawn a conclusion that the best conditions of the degradation of hemicellulase were enzyme concentration is 4mg/mL and liquid-solid ratio is 25:1 with a degradation time of 60h. HPLC showed that the enzymatic hydrolysate of hemicellulose are mainly constituted of xylose, xylobiose, xylotriose, and contained a little monosaccharide and xylooligosaccharide as well.