Preparation Of Xylooligosaccharides From Sugarcane Bagasse

Sodium hydroxide was used to prepare xylan from sugarcane bagasse and xylan was then hydrolysed by xylanase and dilute sulfuric acid to prepare xylooligosaccharides(XOs); The refinery technology for XOs was also investigated. The main results were as follows:1. Xylan preparation and enzymatic hydrolysisXylan was extracted from sugarcane bagasse and used to prepare XOs by enzymatic hydrolysis.20.67% xylan was recovered when sugarcane bagasse was extracted with 15 volume of 4.0% Sodium hydroxide at 30.0℃, under constant stirring at 160 rpm for 24.0 h. The alkali hydrolyzates were ultrafiltrated using hollow fiber ultrafiltrator (3000 Da molecular cutoff) and the concentrate was continously ultrafiltrated by addition of tap water to remove residual alkaline. The concentrate which contained 60.17g/L xylan was hydrolysed by xylanase. The orthogonal test showed that 31.13g/L of XOs with average DP 2.64 (degree of polymerization, DP) was produced when 5.0g/L of xylanase was added and reacted at 40.0℃, pH=6.0 for 4.0 h. The results of small scale tests showed that 9.942 L XOs (concentration=29.62g/L) was prepared when 6 kg sugarcan bagasse was done with the enzymatic process mentioned above. The enzymatic hydrolysis rate was 4.91%.2. Refinery technology for XOsThe effect of four types of activated charcoal and seven types of macroporous ion exchange resins on static decoloration of XOs prepared from sugarcane bagasse were investigated. Results showed that HC-303 powder activated charcoal and macroporous anion ion exchange resin D750 performed best.95.4% of color value was removed and only 4.8% of reducing sugars were lost when 3.0g/L of activated charcoal was added and stirred at 160 rpm, 80.0℃, pH=3.0 for 60min; when 4.50% of macroporous ion exchange resin D750 was added and stirred at 160 rpm,60℃, for 3.Oh,96.5% of color value was removed and 6.0% reducing sugars lost.90% of color value was removed when a cation-anion resin column composed by cation exchange resin 732 and anion exchange resin D750(V732:V750=1:2) was used to adsorb color agent in a dynamic way. The adsorption conditions for the cation-anion column was pH= 7.0, the flow rate was kept at 4.0 BV/h and the column capacity was 8.0 BV. 3. Hydrolysis of xylan by dilute sulfuric acid18.46% XOs was released from sagarcane bagasse xylan by 0.05mol/L dilute sulfuric acid hydrolysis at 100℃for 15min and the DP of XOs was 2.19. The effect of enzymatic hydrolysis was significantly improved when the extracted xylan was hydrolyzed by 0.05mol/L sulfuric acid at 80℃for 90min. The effects of Viscozyme L, xylanase, cellulase or their complex on hydrolysis of sugarcane bagasse were also explored. Results showed that complex addition of the three enzymes (Viscozyme L, xylanase, cellulase) performed best,4.15% soluble sugar was obtained when the dosage of Viscozyme L, xylanase, cellulase was 2%,4%,6%, respectively.Ion chromatography (IC) was used to analyze the components of the acid hydrolyzates refinery XOs. The results showed that the main components of the acid hydrolyzate from the prepared XOs were glucose, xylose, arabinose and galactose.