Biodegradation And Regulation Of Xylan Extracted From Plant Fiber

Xylo-oligosaccharide is a kind of good functional food additive.Using corncob and bagasse as resources, this thesis studied on how to enhance the utilization and the efficiency of enzymatic hydrolysis of xylan, mainly involving the improvement of extracting conditions, enzymatic hydrolysis methods, high temperature pyrogenation of enzymatic hydrolysis residues and rehydrolysis of its product. The experimental results are as followed:1. The proportion of xylan in dry corncob and dry bagasse were 36.85% and 21.44%. In the process of alkaline extraction, by adjusting alkaline volume, temperature and time of reaction, the highest xylan yield from corncob reached to 97.15%, while highest xylan yield from bagasse was only 54.52%. In order to get easy operation and less alkaline volume, the best technological conditions of alkaline extraction of corncob were as followed: alkaline volume was 0.5gNaOH/g dry corncob, the ratio of solid to liquid was 1:7, extraction temperature was 60 ~90 , extraction time was 3.0h; in order to increase extraction rapid, the best technological conditions of alkaline extraction of corncob were as followed: alkaline volume was 0.8gNaOH/g dry corncob, the ratio of solid to liquid was 1:10, extraction temperature was 120 , extraction time was 0.5h. The best technological conditions of alkaline extraction of bagass were as followed: alkaline volume was 0.8gNaOH/g dry corncob, the ratio of solid to liquid was 1:7, extraction temperature was 80 , extraction time was 1.0h.2. Substrate concentration and enzyme dosage did not make obvious impact on the efficiency of enzymatic hydrolysis. When substrate concentrations were 2.86ml, 6.43ml, 10.0ml and enzymatic hydrolysis conditions were at 50 and pH5.5, filtrate xylan yields were almost changeless. So, when substrate concentration was certain, less enzyme dosage was feasible in enzymatic hydrolysis. In addition, several runs of enzymatic hydrolysis could enhance filtrate xylan yield to a certain extent. During the successive four runs of enzymatic hydrolysis, filtrate xylan yields were 53.91%, 14.04%, 10.25% and 8.04%, averge degree of polymerization were 2.1,2.2, 2.8 and 3.2.3. High temperature pyrogenation could enhance the utilization of enzymatic hydrolysis residues. When the reaction conditions were 160 , 170 and 180 , with the increasing of reactive time and temperature, pH and averge degree of polymerization continued to decline,while filtrate xylan yield continued to increase. For the total xylan, the highest filtrate xylan yield could reach to 46.86% in enzymatic hydrolysis residues. Meanwhile, the loss of xylan also continued to increase with the highest loss of 34.15% . The best pyrogenation conditions of xylan in enzymatic hydrolysis residues were as followed: pyrogenation temperature was 180 and pyrogenation time was 40min. Under such conditions, filtrate xylan yield could reach to 46.86%.4. HPLC illustration showed that filtrate xylan yield could increase to 47.22% after high temperature pyrogenation, but in which xylo-oligosaccharides(averge degree of polymerization 2~6) were comparatively lower with the highest proportion of 46.83% in filtrate xylan. Through the rehydrolysis of filtrate xylan after high temperature pyrogenation, xylo-oligosaccharides increased obviously with the highest proportion of 84.93% in filtrate xylan.Meanwhile, the proportion of effective components梮ylobiose and xylotriose in xylo-oligosaccharides also increased obviously with the highest proportions of 57.49% and 18.18% in filtrate xylan.The experimental results of this thesis provided a new convenient method for increasing the utilization and the efficiency of enzymatic hydrolysis of the xylan resources. This method , which had higher applied value, could reduce the practical costs of production and cut down the wastes of production.