【作者】 李晓慧；

【导师】 廖安平； 廖丹葵；

【作者基本信息】 广西大学 ， 化学工艺， 2008， 硕士

【摘要】 右旋糖酐是一种由若干葡萄糖脱水形成的无毒无害的高分子聚合物,是世界上第一个工业化生产的微生物多糖,是最早使用的一种优良的血浆代用品,在医药、食品和石油等方面都有着广泛的应用。本课题选用中国工业微生物菌种保藏中心的肠膜明串珠菌20074,以蔗糖为底物发酵制备右旋糖酐。研究了发酵液中右旋糖酐沉析条件及右旋糖酐分子量的测定方法,菌种的培养条件,发酵工艺条件,并初步探索了固定化菌体的方法制备右旋糖酐。获得的最适合肠膜明串珠菌20074生长的培养基组成为:蔗糖10%、蛋白胨0.2%、磷酸氢二钠0.2%、磷酸二氢钾0.03%、酵母浸膏0.5%。获得的最佳发酵条件为:种子液发酵时间10-12h,接种量约10%,培养基pH值7.0-7.5,培养温度28℃,转速为50r/min,发酵时间20-24h,底物浓度15%,维生素E和Mn²⁺有利于右旋糖酐的形成,配置成一定浓度溶液作为添加剂加入到发酵培养基中,加入量为0.8mL/L。用高效凝胶渗透色谱法测定发酵液中右旋糖酐分子量大于40万,用红外光谱表征产品结构中的特征基团与标准品相符。活性炭是较好的固定化菌体的载体,肠膜明串珠菌20074在活性炭上的最佳固定化条件为:培养基初始pH值为7.10,接种量10%,固定化时间10-13h,摇床转速150r/min,固定化温度25℃。固定化菌体方法制备所得的右旋糖酐与直接发酵法制得的产品在分子量和结构上都相同,但产率有所降低。更多还原

【Abstract】 Dextran is a kind of polymerization composing by glucose dehydrating,is of innocuity,is the first microbiology polysaccharid produced in industry, is the substitute of blood plama used at first,is used widely in medicament, food and petroleum.In this subject, Leuconostoc mesenteroides 20074 bought from CICC is choosed,preparing dextran by fermenting when sucrose is used as substrate.The culture condition,precipitating condition of dextran in fermenting culture medium, method of measuring molecular weight of dextran and fermenting condition are investigated, research of preparing dextran by immobilizing Leuconostoc mesenteroides 20074 is done primarily.The optimal composition of Leuconostoc mesenteroides 20074 culture medium is: sucrose 10%, peptone 0.2%, Na₂HPO₄ 0.2%, KH₂PO₄ 0.03%, yeast extract 0.5%.The best technology condition: fermenting time of Leuconstoc Mesenteroides 20074 10-12h, transferring content 10%, pH of culture medium 7.0-7.5, culturing temperature 28℃, vibrator speed 50r/min, fermenting time 24h, consistency of substrate 15%, vitamine E and Mn²⁺ is available for dextran forming and content of vitamine E and Mn²⁺ with certain consistency is 8mL/L. The molecular weight of dextran producd by fermenting is more than 400,000 measured by HPGPC, and the IR spectrum of dextran is accordant with the IR spectrum of standard sample.Active carbon is a better carrier,the best technology condition of immobilizing Leuconostoc mesenteroides 20074 on active carbon is: pH of culture 7.1, transferring content 10%,immobilizing time 10-13h, vibrator speed 150r/min,immobilizing temperature 25℃.The molecular weight and structure of dextran is accordant with dextran preparing by fermenting, and the yield rate of dextran decreases.更多还原