Immobilized Cell Biotransformation Hemicellulose Hydrolyzate Production Of Xylitol

The research work in this thesis includes: preparation corn cob hemicellulosic enzymatic production and xylitol fermentation from corn cob hemicllucellulosic, enzymatic hydrolysate , microcapsule was applied in xylitol of corn cob hemicellulosic enzymatic hydrolysateCorn cob is composed of lignin cellulose and hemicellulose.It is difficulte to directly enzymatic hydrolysate.we must be pretreated .we select high temperature cooking solubility of the xylan . the optimum conditions were as follows:corn cob was pretreated by 0.1% acid at 60℃ for 12h. The best proportion of corncob with the water is 1 :10, high temperature cooking temperature is 170℃, reaction time is 2h. the optimum conditions of enzymatic hydrolysate as follows: xylanase 6% , at pH4.0 ,45℃, 200r/min reaction 8h in xylitol fermentation of corn cob hemicellulosic enzymatic production, the optimum conditions were as follows:xylose 40g/L, culture medium 100 ml in 250 ml flask, inoculum size, 5%; inoculum age, 20 h; nitrogen source. 2.5 g/L Bacto-yeast extract and 2.5 g/L Bacto-tryptone,temperature 30℃,In this condition ,the highest xylitol yield 66.35%.In order to evaluate the effect of aeration rate on the xylitol fermentation on corn cob hemicellulosic enaymatic production in fermentator ,batch fermentation were carriec out two-stage aeration strategies,which provided relative higher aeration rate in the early stage but reduced it in the later stage,and including a one-stage aeration strategy that it provbided a constant aeration rate.The two-stategy oxygen supply strstegy is 2.0wm for the fist 20h,then lowered it to 1 .0vvm.The preparation process of chitosan-alginate microcapsule is 0.5%chitosan solution (dissolved in 1% HAc, pH 6) and a simple droplet generator were employed to form chitosan-alginate microcapsules The best reaction time of the membrane's construction of microcapsules was found to be 15min, and the best reaction time of the liquefying of microcapsules to be 25min.Chitosan-alginate microcapsule was applied in xylitol batch fermentation. Themicrocapsules were used repeatedly in four batches. It was found that the fermentation with microcapsules had better and fixed conversion (55.17%), comparing with free-cells fermentation (changed from 67.5% to49.87%) and Ca-alginate immobilizing fermentation (changed from 41.23% to 45.67%), while the end time of microcapsule fermentation was enhanced and fixed to 64h.The chitosan-alginate microcapsuleused for xylitol productin on corn cob hydrolysates. The optimum batch fermtentation conditions was as follows:shaking speed was divided into two stages:200r/min 0-20h,140r/min at 20-64h. nitrogen source. 2.0 g/L Bacto-yeast extract and 2.0g/L Bacto-tryptone,the volume propotion between gel beads of immobilized cells and hydrolysates.The research work of thesis developed an xylitol fermentation process using corn cob hemicellulosic enzymatic hydrolysate in stead of acid hydrolysate .The technology is of importang value.