Studies On Production Of Xylooligosaccharides From Corncob With Xylanase

Xylooligosaccharides are oligasaccharides composed of xylose units linked by β-1,4-xylosidete bonds. They are highly-effective Bifid bacteria improver and have good physiological activities, and are widely studied all over the world. This dissertation systemically studied the processing of the xylooligosaccharides production with enzyme, including the extraction of corncob xylan, the hydrolization of xylan by xylanase, the refinery of the raw xylooligosaccharides solution and the separation of the components of xylooligosaccharides.The processing of the corncob xylan extraction was established through orthogonal test as the followings: corncob powder was mixed with 0.7 mol/L sodium hydroxide at the ratio of 1:10(w/v); the mixture was heated to 120℃ for 30 min and then filtrated; the filtrate was alcoholized to the final alcohol concentration 65%, and then centrifuged, and the deposit was collected. Under this condition, the yield of corncob xylan is 16.63% in a 100 L reactor. Xylanase produced by Bacillus pumilus WUN024 had different effect on different xylan, that were good on the easy solubilized birch wood and bad on the difficult solubilized oat spelt, and the soluble xylan had better effect than the insoluble xylan. The processing parameters of xylan hydrolysis by xylanase were optimized as the substrate concentration 10%, xylanase dosage 800 IU per gram substrate on 40℃ for 6 h. Under this condition, the yield of xylooligosaccharides is 66.29%. Stiring rate in hydrolysing reactor effected the yield of xylooligosaccharides, and the better yield 50.25% was attained at 300 r/min. Insolvable xylan was treated with 0.1% vitriol at 120℃ for 30 min, then dealt with xylanase(800 IU per g substrate) for 6 h. The DP of xylooligosaccharides obtained from insolvable xylan is 1.43 and the yield is 13.6%.Activated carbon and ion exchange resin were commonly used in xylooligosaccharieds refinery. The absorption effects on coloring matters were evaluated with Freundlich Equation, and activated carbon Ly-T-ac and anion exchange resin D-301G were chosen as pigment sorbents. The optimum condition for decoloration with activated carbon was pH 5.0, 80℃, 30 min treatment and 3% carbon dosage. Under this condition, 81.1% of the pigment was removed and 15.26% of the xylooligosaccharides were lost. By using 8% anion exchange resin D-301G at 40℃ for 3 h, 42.1% of the pigment was removed, and after treated with ion exchange resin D-301G and 732, 61.45% salt was removed. The HPLC showed that 65.52% of the refined oliosaccharides are xylobiose and xylotriose, and more than 98% are xylooligosaccharides.The xylooligosaccharides components were separated on activated carbon chromatography eluded with alcohol. The results showed, all xylose and part of xylobiose can be washed out with 13% alcohol; xylotriose and higher DP sugar can be washed out when eluded with 30% alcohol.