Study On The Preparation Of Xylooligosaccharides From Steam-exploded Corncob By Xylanase Of Streptomyces Cirratus D-10

This study covers the researches on the extraction of corncob xylan by steam-explosion, the optimal condition of Streptomyces cirratus D-10 xylanase hydrolyzing steam-exploded corncob and purifing the hydrolyzed steam-exploded corncob by yeast, The conclusions are as follows:1.The effects of explosion pressure, reaction time and ratio of corncob with water on the extraction rate of xylan, the soluble value of lignin and the degree of polymerization of xylan were investigated. It is found that explosion pressure and extraction rate of xylan are positive correlation, while with the pressure increasing, the D.P. increases firstly and then decreases; The longer the reaction time is, the more the extraction rate of xylan and lignin; The D.P. will decrease with the increasing reaction time, however, excess reaction time will lead to the excess degration of xylan. With the increase of ratio of corncob with water, the amount of lignin increases, while the amount of xylan and the D.P. increases firstly and then decreases. It is concluded that optimal ratio of corncob with water is 1 : 20.2.The optimal conditions of Streptomyces cirratus D-10 xylanase hydrolyzing steam-exploded corncob and alkali-extracted corncob xylan were studied. It is obtained that 80 U/ 100 mL of the enzyme concentration hydrolyzing for 6 h and 60 U/g of the enzyme concentration hydrolyzing for 8 h are the optimal conditions of the Streptomyces cirratus D-10 hydrolying the steam-exploed corncob and alkali-extracted corncob xylan, respectively. It is shown that the xylanase is more effective on the steam-exploed corncob than on the alkali-extracted corncob xylan, and steam-exploed corncob is a more suitable substrate for Streptomyces cirratus D-10 xylanases to prepare xylooligosaccharides.3.In this study, we also selected an yeast, which can metabolize selectively xylose and arabinose, but can not degrade xylobiose. Xylose and arabinose in the hydrolysate of the steam-exploded corncob are fully consumed with 10 % inoculation at 48 h, while the mount of the xylooligosaccharides don't change notably. After purification by the yeast, the main compontents of the hydrolysate of the steam-exploded corncob are xylobiose and xylotriose.