木糖酸辅助水解木聚糖制备低聚木糖及其分离与回收工艺研究

Preparation of Xylooligosaccharides by Xylonic Acid Assisted Hydrolysis of Xylan and Its Separation and Recovery Process

以玉米芯碱抽提木聚糖为原料,设计了木糖酸质量浓度、反应温度及反应时间3因素3水平的响应面试验以确定木糖酸辅助水解木聚糖制备低聚木糖的最优条件,同时通过氧化葡萄糖酸杆菌的生物氧化作用将木聚糖水解液中的木糖转化为木糖酸,最后通过电渗析装置实现了木糖酸与低聚木糖产品的分离与回收。研究结果表明:固液比1∶10(g∶mL)的条件下,木糖酸质量分数6%,反应温度170℃,反应时间22 min的条件下,低聚木糖质量浓度达到38.4 g/L,得率为54.9%。此外,未经处理的酸水解液中的18.5 g/L木糖可在12 h内直接经由4 g/L氧化葡萄糖酸杆菌氧化为18.2 g/L的木糖酸,木糖利用率91.6%,木糖酸得率为90.9%,酸水解液中木糖酸总质量分数由6%提升至7.8%,最后该发酵液通过双极膜电渗析可实现木糖酸与低聚木糖的分离与回收,二者的回收率分别为95%和98%,低聚木糖纯度由30%提高到75%。

Using reaction temperature,xylonic acid(XA-H)mass fraction and reaction time as independent variables,a response surface design was employed to optimize the yield of xylooligosaccharides(XOS)from acidic hydrolysis of the alkali extraction xylan obtained from corncob.And the Gluconobacter oxydans was used to bio-oxidize by-products xylose to XA-H.Then,XA-H and XOS products were simultaneously separated and recovered by bipolar membrane electrodialysis.The results indicated that the optimal conditions for producing XOS were solid-to-liquid ratio 1∶10(g∶mL),reaction temperature 170℃,mass fraction of XA-H 6%,and reaction time 22 min.Under the optimum conditions,the yield of XOS was 54.9%,while 18.5 g/L xylose was generated as byproduct.Sequentially,the xylose was converted into XA-H within 12 h with C.oxydans of 4 g/L(mass concentration 18.2 g/L,yield 90.9%)cells,and the total content of XA-H increased from 6%to 7.8%.Finally,the hydrolysate after biooxidation was subjected to electrodialysis for separating the XA-H and XOS;the corresponding recovery rates were 95%and 98%,respectively,the purity of XOS was increased from 30%to 75%.