| With the development of the society and people's life pace becoming faster and faster, all kinds of health problems have significantly appeared. Oligosaccharide is one of high quality bifidus factor that has a good effect on human intestinal health and great commercial value. In this paper, wheat bran(WB) and cottonseed hull(CH) which were both agricultural waste were selected as raw materials, and high temperature cooking method was applied to optimize the xylan extraction condition. On that basis, the hydrolysis reaction kinetics of hemicellulose was studied. Then the selected optimum conditions was conducted in amplification experiments, which can provide theoretical basis for the industrial production of oligosaccharide. The main results were as follows:(1) The de-starch WB and acid-alkali treated CH was used as raw materials to explored the effect of stock-to-liquid, acid species and concentration during the extraction process of xylan on the content and average polymerization degree of soluble pentosan in 350 mL glass pressure bottle under the temperature of 160 ?. The single factor experiment showed that the optimum condition of WB is stock-to-liquid 1:20 and acetic acid concentration 0.012 mol/L; CH is stock-to-liquid 1:15 and sulfuric acid 0.024 mol/L.(2) Both of two stocks' hydrolysis behavior followed the first-order continuous reaction kinetic model, and simulation results matched the experiment results well. Under high temperature conditions the concentration of soluble pentosans significantly improved, but the soluble pentosan concentration decreased rapidly in a short time. The temperature and time of reaction are the main factors that influenced the hydrolysis process of lignocellulosic biomass, but the dynamic behaviors of the materials are significant difference. This difference mainly stems from different content and structure of lignocellulose. The extraction activation energy(Ea1) of WB and CH xylan is 74.81 and 49.42 kJ/mol respectively; The xylan degradation activation energy(Ea2) is 83.05 and 66.30 kJ/mol respectively.(3)The temperature, time and acid concentration which had greater impact of the xylan extraction were selected for orthogonal experiment, and the each optimal conditions are as follows:the WB and 0.006 mol/L acetic acid were blended by the ratio of 1:20, cooking at 180? for 25 min, when the concentration of soluble pentosane was 15.19 g/L and the average degree of polymerization(DPa) was 2.41, the sugar yield of WB was 17.01%; The alkali-acid treated CH and 0.006 mol/L sulfuric acid were blended by the ratio of 1:15, cooking at 190? for 15 min, when the concentration of soluble pentosane was 27.21 g/L, DPa was 2.84, and sugar yield of CH was 22.85%.(4) The amplification experiment under optimal process conditions failed to reach the optimal level both in soluble pentosane content and DPa. The process conditions was optimized by reducing the reaction time and temperature. Finally WB was treated in 170? for 20 min, when the concentration of soluble pentosane was 10.19 g/L, DPa was 2.25, and sugar yield of WB was 11.41%; CH was treated in 170? for 35 min, when the concentration of soluble pentosane was 18.89 g/L, DPa was 2.37, and sugar yield of WB was 15.86%. The high-performance liquid chromatography(HPLC) was applied to analyze the composition of sugar liquor enzymolysis by xylanase. The results showed that:sugar degradation phenomenon under amplification experiment was worse than that under laboratory conditions. WB sugar liquor's monosaccharide component includes xylose, arabinose and glucose, which is complex than CH. |
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