| China is a major country producing cotton in the world,and the cotton seed shell is rich. Actually the way of use cottonseed shell is unitary and the biological utilization rate is extremely low. Looking for a new utilization way and improving the value of cottonseed shell are urgently to solve. Xylan which comes from cottonseed shell can degrade xylo-oligosaccharide, xylo-oligosaccharide is a kind of functional oligosaccharides. It is stable and difficult to be digested in the human body. It can reduce diarrhea, prevent constipation, anti-cancer, lower blood pressure, etc. Therefore, isolation and purification of xylo-oligosaccharides from cottonseed hull is another way. It mainly includes following respects:(1) Xylan was extracted from cottonseed hull mainly uses two methods: ultrasonic assisted alkali method and microwave assisted alkali method. Basing on the experiment of single factor, the optimum extraction cindition were determined respectively.Ultrasonic temperature 60℃, ultrasonic time 30 min, solid-liquid ratio 1:15, Na OH concentration 8%, and the xylan extraction rate was 33.66%; solid-liquid ratio 1:15, Na OH concentration 12%, microwave power 400 W, microwave time 6min, the extraction rate of xylan was 43.23%.(2) Preparation of xylo-oligosaccharides from xylan by xylanase hydrolysis.Select enzyme amount, enzyme time, enzyme temperature and solid-liquid ratio as single factor, On the basis of single factor, the optimum process of enzymatic hydrolysis was obtained by using the response surface optimization: solid-liquid ratio 1:20, the amount of enzyme 4%, enzyme time 3.5h, enzyme temperature 64℃, the xylo-oligosaccharides in the enzyme solution was 3.35mg/m L.(3) Decolorization of hydrolysate of xylo-oligosaccharides, three methods of active carbon discoloration, chemical decolorization and decoloration with resin were compared, it comed to the conclusion: the effect of resin was better than the other two methods, the decolorization rate was as high as 61.77%, the recovery rate of xylo-oligosaccharides was 91.88%.Further study on the decolorization of resin, six kinds of resins were selected for initial screening, the highest decolorization rate was 76.84% of D392, the recovery rate of xylo-oligosaccharides was 91.58%. Select resin addition, decolorization time, decolorization temperature, p H as single factor, On the basis of single factor, the optimum process of decolorization was obtained by using the response surface optimization:resin added amount 5%, decolorization time 3h, decolorization temperature 55℃, p H7, at this time the decolorization rate was 78.06%. Dynamic decolorization of D392 resin, obtained the optimum bleaching time was 198 min, the optimal flow rate was 1.0m L/min, the best resin dosage was 120 m L.(4) Purification of xylo-oligosaccharides hydrolysate, the enzyme solution was ultrafilter under the pressure of 0.5MPa through hollow fiber ultrafiltration membrane.The conductivity decreased from 11.60ms/cm to 7.56ms/cm; the color value decreased from 0.27 to 0.11; the xylo-oligosaccharides content decreased from 3.08mg/m L down to 2.82mg/m L, the recovery rate was 91.56%. Using sephadex chromatogram to obtain an oligosaccharide solution of 92.81% purity. After rotary evaporation, madding xylo-oligosaccharides into powder form by spray drying.(5) Using xylo-oligosaccharides powder prepared into the concentration of 3.5mg/m L solution and analysised the components of the xylo-oligosaccharides by high performance liquid chromatography. The peak time of xylose, xylobiose, xylotriose, xylotetraose was 13.67 min, 11.24 min, 9.73 min, 8.68 min, the content was 149.90 μg/m L,1229.60 μg/m L,1737.40 μg/m L, 281.30μg/m L respectively. |
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