玉米秸秆半纤维素制备木糖醇的研究

首先采用无污染的碱性过氧化氢法研究了半纤维素的分离与提取,然后对提取的半纤维素分别进行化学水解和酶水解比较,最后研究了水解液发酵制备木糖醇。结果表明,半纤维素分离提取的优化参数为:2%过氧化氢,2%氢氧化钠,加热时间4 h,反应温度75℃。使用CF3COOH水解半纤维素所得木糖含量为67%~73%,水解率为76%~84%,稀盐酸预处理半纤维素再化学水解所得木糖含量高达88%,水解率上升至大约90%。半纤维素的酶水解实验表明,木聚糖酶的水解专一性高于半纤维素酶,木聚糖酶水解率为38%~60%。在水解液发酵实验中,酶水解液的木糖醇转化率高于化学水解液。另外,通过浓缩半纤维素水解液,提高发酵液的木糖初始浓度,有利于菌株生长,可以提高木糖醇转化率。研究对于玉米秸秆半纤维素制备化学品具有一定的指导意义。

Preparation of xylitol from corn stalk hemicelluloses

The extraction and separation of hemicelluloses by using alkali peroxide were studied,chemical hydrolysis and enzymatic hydrolysis of extracted hemicelluloses were compared,and fermentation of the hemicellulosic hydrolysate to prepare xylitol was researched.The experimental results showed that the optimized parameters for isolation of hemicellulose was:2% hydrogen peroxide,2% sodium hydroxide,heating time 4 h,reaction temperature 75 ℃.The content of xylose hydrolyzed hemicellulose by CF_3COOH is 67%～73%,the hydrolysis rate is 76%～84%.The xylose content with hydrochloric acid pretreatment rose to 88%,and the hydrolysis rate rose to around 90%.The results of enzymatic hydrolysis show that the specificity of xylanase is higher than hemicellulase.The hydrolysis rate of xylanase was about 38%～60%.The conversion rate of xylitol in enzymatic hydrolysate is higher than chemical hydrolysis.In addition,concentrating the hemicellulosic hydrolysate to improve the initial concentration of xylose in fermentation broth is good for the growth of strains,which can improve the conversion rate of xylitol.The study on preparation of chemicals from straw hemicelluloses is significant for future production.