一株产絮凝剂芽孢杆菌的分离鉴定及絮凝剂特性分析

摘要

从山东及河北沿海分离到一株严絮凝剂细菌(编号200903091102,简称1102),分别用细菌全脂肪酸气相色谱法和16S rDNA序列分析比对法对该菌进行鉴定,两种方法的鉴定结果均显示细菌1102为一种芽孢杆菌(Bacillus sp.).系统发育分析显示,细菌1102与枯草芽孢杆菌(B.subtilis)、特基拉芽孢杆菌(B.tequilensis)等亲缘关系最近.应用高氏1号培养基培养细菌1102,提取其絮凝剂进行絮凝力测定,结果显示,该菌所产絮凝剂的絮凝率达到80.19％.发酵72 h时,絮凝剂得率最高达19.5 g/L;分别采用凝胶渗透色谱法、苯酚-硫酸法及氨基酸自动分析仪对所得絮凝剂的相对分子质量、多糖含量及氨基酸含量进行分析,结果显示絮凝剂的重均相对分子质量为7 063 D,多糖质量分数占58.58％,氨基酸质量分数占2.49％.提示该菌在海水养殖中将具有较高的开发价值.本研究旨在为海水养殖废水的生物净化提供科学依据.%Microbial bioflocculants (MBF) may be produced by various kinds of bacteria. They are usually composed of glycoprotein, polysaccharide, cellulose and nucleic acid. As MBF can agglutinate suspended solids in waste water and can be easily broken down by microorganisms in the environment, they have potential application in the sewage treatment industry. In aquaculture, some microorganisms that are able to produce MBF play an important role in the conversion of food energy and in the maintenance of the stability of the ecological systems in fish and shrimp ponds. In this study, we isolated a flocculant-producing bacterium numbered 200903091102 (hereinafter referred to as 1102) from coastal water of the south coast of Laizhou Bay China. Methods including 16S rDNA sequence analysis and gas chromatographic whole-cell fatty acid analysis were employed to identify the bacterium 1102. To analyze its flocculating activity, the MBF was extracted and purified from the fermentation broth of bacterium 1102 that had been fermented in Gauze's medium No.l for 96 h. Bacterium 1102 is a Bacillus sp. genetically related to B. subtilis, B. tequilensis, B. mojavensis and B. amyloliquefaciens. The flocculation rate of bacterium 1102 was 80.19%. The highest yield of MBF (19.5 g·L-1) was obtained 72 h after inoculating. Further studies were carried out to investigate the molecular weight of MBF, the total polysaccharide content, and amino acid content, by gel permeation chromatography, phenol sulfuric acid colorimetry, and automatic amino acid analysis, respectively. The average molecular weight of MBF was about 7 063 D, the polysaccharide content was 58.58%, and the amino acid content was 2.49%. We discuss the potential application of bacterium 1102 to aqua-culture. Bio-floc technology (BFT) has been used in fish and shrimp culture in many countries and shows a great potential for in increasing food conversion rate and for zero water exchange. BFT usually depend on microorganisms that are able to produce MBF in the culture system. Bacterium 1102 is highly efficient for production of MBF at high flocculation rates and can be used in marine aquaculture to flocculate organic detritus and microalgae in ponds. In addition, bacterium 1102 is a Bacillus sp. which may be helpful because many species of bacillus are probiotic for aquaculture.