微生物絮凝剂MBFGA1的结构鉴定及絮凝机理研究

摘要

With the flocculating rate of kaolin as index, flocculating activity analysis of various components in fermentation liquor was conducted, and it was confirmed that MBFGA1 fine product was nuclear effective component of the micro-bioflocculant. MBFGA1 fine product was acquired through purificating the coarse product(obtained from fermentation liquor by acetone extraction) using sevage reagent, identified to be polysaccharides employing full spectra scan, phenol sulfuric acid method and coomassie blue staining, and separated as MBFGA1-1 and MBFGA1-2 through twice gel chromatography separation filter. The structure of MBFGA1, MBFGA1-1 and MBFGA1-2 was analyzed adopting ESEM, EDS, FTIR, HPLC and GC. Results demonstrated that MBFGA1 had a linear long chain molecular structure, in which α-glucosidic bonds primarily existed among monosaccharides, and perssads with good effect of coagulation such as hydroxyl, carboxyl, methoxy;MBFGA1-1 was homogenous with the weight of 1.18×106 and mainly composed of xylose, mannose, glucose (0.3:1:1.09), and a bit of rhamnose; MBFGA1-2 with the molecular weight of 3.08×103D, and rhamnose, xylose, mannose, galactose and glucose (0.68:0.28:1.82:1:3.73) as its monosaccharide formation. The main flocculating mechanism was adsorption bridging, meanwhile the high molecular weight and polar groups made the long chain structure molecules well stretched, and played good role in adsorption bridging.%以对高岭土的絮凝率为指标对GA1发酵液中各组分的絮凝活性进行预分析,确定MBFGA1精产品为该絮凝剂的核心有效成分.通过丙酮沉淀法提取MBFGA1粗产品,经Sevage试剂纯化后得到MBFGA1精产品,采用全波长扫描、苯酚-硫酸法及考马斯亮蓝法鉴定精产品为多糖类物质,并经2次凝胶过滤层析分离获得MBFGA1-1和MBFGA1-2两组分；分别使用电镜(ESEM)、红外光谱(FTIR)、高效液相色谱(HPLC)以及气相色谱(GC)对MBFGA1、MBFGA1-1和MBFGA1-2进行检测分析.结果显示MBFGA1为线性长链状分子结构,多糖主链上单糖间的连接主要为α-型糖苷键,含有羟基,羧基,甲氧基等有利于絮凝的基团；高效液相色谱和气相色谱测定MBFGA1-1分子量为1.18×106D,单糖组成为0.3木糖∶1甘露糖∶1.09葡萄糖,另含有少量鼠李糖；MBFGA1-2分子量为3.08×103D,单糖组成为0.68鼠李糖∶0.28木糖∶1.82甘露糖∶1半乳糖∶3.73葡萄糖.根据分析结果推测絮凝机理主要为吸附架桥,其中MBFGA1的大分子量以及所含的极性基团使得絮凝剂长链结构分子能够充分伸展,较好地发挥吸附架桥作用.