Study On Preparation Of Xylooligosacchrides From Corncobs By Enzyme System

Since the functional oligosaccharides have some physiological functions, such as promoting the multiplication of Bifidobacteria in intestine, keeping a good healthy for people, the functional oligosaccharides have been attached important to by the people. A xylooligosaccharide is a kind of functional oligosaccharides, composed of 2-7 xylose. The link between the molecules is β-1,4-xylosidate band. It can be prepared by β-xylanase reaction with corncob, cotton, seed hull or rapeseed hull. It's very difficult for xylooligosaccharide's digestion in intestines. The intestinal survivors of xylooligosaccharides are too much, and can keep a good multiplication for Bifidobacteria. The utilization of the xylooligosaccharide is the highest among the other oligosaccharides. A maize is one of three main foodstuff plants in China. The average yield of the corncob is very big. Most of the corncobs are burnt, although a few are used. It's very important to do the research about the xylooligosaccharides preparation with corncobs.The xylan from agricultural residues corncabs was enzymatic hydrolyzes into crude xylooligosaccharides with xylanases by Asperglllus nlger and purified xylooligosaccharides through the active carbon. And a capillary electrophoresis method for determination of main components in xylooligosaccharides was described.After pretreatment, the optimum extract process conditions of xylan were as follows: the ratio of water and corncobs was 10, and the concentration of NaOH was 10%, 100℃ for 2 h. Neutralized with HC1, The deposit was dried and got crude xylan. The yield of crude xylan was 22.7% (g crude xylan/ g corncob).The Asperglllus nlger's optimal culture conditions were as follows: corncob meal: carbon source C= 6:4, 1% of nitrogen source N₁ in dry medium weight, dry medium: water= 1:2, temperature was 28 ℃ and cultivation for 84 hours. The conditions of extraction xylanase were as follows: the dry culture was extracted with 0.05 mol/L acetic acid buffer (pH 4.6) for 2 h, the ratio between the solid culture and the extracting agent was about 1:5 (w/v). After filtrated, the (NH₄)₂SO₄ was used to salt out for 1.5 h. The saturation condition of (NH₄)₂SO₄ was 70%. The deposit was freezed-dry, the crude enzyme was got. The optimal temperature for xylanase activity was 45 ℃ and optimal pH value was 3.6. Xylanase activity was stable below 50℃ and pH 3.0 to pH 11.0. The common metal cation has little effect on the enzyme. So the enzyme is fit to the industrial production of xylooligosacchrides.The xylan was enzymatic hydrolyzes into crude xylooligosaccharides withxylanases. The optimum conditions were at 45 °C, pH 3.6, the agitation rate was 200 r/min, the reactive time was 4 hours, xylan 2 g/50 ml and xylanase lording 1% (v/v), the xylooligosaccharides' concentration was 4.02 mg/ml and 44.18% of total sugar.The xylooligosacchrides was absorbed by active carbon column. After purged by distilled water, 15% ethanol was used to purge and get purified xylooligosacchrides. The purity of xylooligosaccharides was 82.6%, the recovery was 78.1%.A capillary electrophoresis method for determination of main components in xylooligosaccharides was described. The influence of various separation conditions including buffer concentration, pH value and voltage were investigated. By using an uncoated silica capillary (75 um I.D, 40 cm bf total length, and 30 cm of efficient length) and 75 mmol/L borax (pH 10.5) as carrier electrolyte, the derivatized xylooligosaccharides with a-naphymethamine, the main components of xylooligosaccharides were sufficiently separated at the qualification of an applied voltage of 10 kV and a UV detection wave-length of 214 nm. The result indicated that the relative standard deviations for xylobiose's migration time and peak area were all less than 0.5%, and 2.0% respectively. Quantification by the peak area method allowed reproducible determination of analyte at the concentration range of 0.0001¹.000 mg/ml. This method is characterized by its sensitivity, reproducibility and low cost, should be useful for the determination of main components in xylooligosaccharides formulation.