【作者】 李艳；

【导师】 李志西；

【作者基本信息】 西北农林科技大学 ， 粮食、油脂及植物蛋白工程， 2013， 硕士

【摘要】 细菌纤维素（Bacterial Cellulose，BC）是由醋杆菌属等细菌异养产生的凝胶膜状物。与植物纤维素和动物纤维素相比，它是一种“超纯净”的纤维素，不掺杂其他多糖，具有许多优良特性。目前广泛应用于食品、声音器材、造纸、石油开采、医药等多个领域。本研究以长有BC膜柿子醋为材料，分离筛选BC高产菌株，优化发酵工艺参数，进行发酵动力学的初步探索，并对BC结构性质进行研究，得到以下研究结果：(1)经分离纯化获得一株BC高产菌株—L96，遗传性能稳定。经16S rDNA基因序列测定、系统发育树分析、生理生化试验等，确定该菌株为木葡糖酸醋杆菌(Gluconacetobacter xylinus)。(2)菌株L96静态条件下的最佳发酵培养条件是：种龄20h，初始pH值4.0，接种量11%，30℃培养9d。最适发酵培养基成分为：蔗糖5%(w/v)，酵母膏0.9%(w/v)，蛋白胨0.5%(w/v)，K2HPO40.3%(w/v)，MgSO42%(w/v)，乙酸0.2%(v/v)，乙醇1.5%(v/v)。采用优化后的发酵培养条件和发酵培养基，L96的BC湿膜平均产量为68.37g/100mL，是优化前(48.93g/100mL)的1.4倍。(3)菌体密度和BC生成量随糖度的消耗而增加，发酵生产BC属于生长偶联型。pH值随菌体生长和BC生成量增加而降低。(4)L96所产BC平均干重为0.37g/100mL，干膜中纤维素含量为89.24%，蛋白质含量为6.33%，脂肪含量为0.96%。扫描电镜观察结果显示该菌株合成的BC具有超微细网状结构，膜的持水量为130～210g/g干膜，干膜平均复水率为70.60%。更多还原

【Abstract】 Bacterial Cellulose (BC) is a kind of gelatinous membrane produced by bacteria such asAcetobacter on heterotrophic mechanism. Compared with plant fibers and animal fibers, it is akind of "super-pure" cellulose and isn’t mixed with any other polysaccharide. It has a lot ofgood qualities. BC has been widely used in the areas of food, high-grade acoustics, papermaking, oil drilling and medicine etc today.Persimmon vinegar with BC membrane was used as raw materials to isolate and obtain acellulose-producing strain with highproductivity and genetic stability, and the parameters offermentation process were optimized. Synthesis kinetics of the production was preliminarilyexplored and the structure and property of the BC was studied. The main research results areas follows:(1) Through separation and purification, a cellulose-producing strain—L96, with highproductivity and genetic stability was obtained. Accroding to the16S rDNA sequenceanalysis and phylogenetic tree analysis and physiological and biochemical analysis, this strainwas identified to be Gluconacetobacter xylinus.(2) The optimum cultivation conditions were as follows: seed ages20h, initial pH value4.0, inoculums amount11%, incubation time9d. The optimum fermentation medium were asfollows: sucrose5%(w/v), yeast extract0.9%(w/v), peptone0.5%(w/v), K2HPO40.3%(w/v),MgSO42%(w/v), acetic acid0.2%(v/v), ethanol1.5%(v/v). Using the optimized fermentationculture conditions and fermentation medium formula, the wet film weigh of BC was68.37g/100mL, which was as1.4times as that under initial fermentation medium(48.93g/100mL).(3) Bacteria density and BC production increased with the sugar concentration decreased.The fermentation process of producting BC belonged to the process of growth wasmembrane-associated. The pH value decreased with the bacteria density and BC productionincreased.(4) The average dry film weighs of BC synthesized by L96was0.37g/100mL, cellulosecontent in dry membrane was89.24%, protein content was6.33%, and fat content was0.96%.The images of scanning electron microscope (SEM) showed that BC synthesized by L96was ultrafine network structure. Moisture content of per gram of dried cellulose was130~210g, average rehydration rate of dried cellulose was70.60%.更多还原