【作者】 黄凯；

【导师】 李小明； 曾光明；

【作者基本信息】 湖南大学 ， 环境工程， 2004， 硕士

【摘要】 微生物絮凝剂是一类由微生物产生并分泌到细胞外具有絮凝活性的代谢产物，具有良好的絮凝沉淀性能，安全、无毒，易于生物降解。由于其克服了无机和有机絮凝剂在使用安全和环境污染方面的问题，所以研究和开发微生物絮凝剂具有重要的现实意义和广阔的应用前景。 本课题采用常规的分离、纯化方法，从长沙市某污水处理厂活性污泥、岳麓山土样、湘江畔污泥中分离筛选出5株产絮凝剂的菌株，复筛得到1株絮凝活性较高的微生物絮凝剂产生菌，经初步鉴定为气单胞菌属，定名为Aeromonas sp．N11。以Aeromonas sp．N11为研究对象，研究了培养条件和培养基成份种类及其用量对菌产微生物絮凝剂的影响，同时对其所产微生物絮凝剂的絮凝特性也进行了研究。 实验结果表明，培养基的成份及其用量对菌产絮凝剂具有重大影响。通过单因子实验和正交实验发现，较高的C／N比对菌产絮凝剂有利；碳源中的蔗糖是菌株Aeromonas sp．N11产絮凝剂的良好碳源；氮源以采用复合氮源为佳；培养基中加入酵母膏有利于絮凝剂的产生；NaCl能够促进所产絮凝剂的絮凝活性；碳源蔗糖和有机氮脲对菌产絮凝剂的影响最大；根据正交实验结果确定产絮凝剂优化培养基组成为：蔗糖20g／L，酵母膏0.8g／L，脲0.5g／L，硫酸胺0.5g／L，NaC17g／L。适宜的培养条件是：pH值7，温度为30℃，摇床转速170r／min，培养时间72h。 对Aeromonas sp．N11所产絮凝剂的絮凝特性实验发现，N11絮凝活性由菌细胞生长后期的次生代谢产物产生，絮凝物质主要存在于发酵液中。除Fe³⁺离子在较高浓度时抑制絮凝作用外，本实验中各类一价阳离子和二价阳离子对絮凝都有促进作用，其中以K⁺、Na⁺、Ca²⁺三种阳离子助凝效果最好。对不同的被絮凝物质絮凝剂和助凝剂具有不同的最佳投加量。pH值、温度等条件都能够影响絮凝剂的絮凝活性。该絮凝剂的最适pH值跟助凝剂的种类和被絮凝物质有关。100℃水浴加热1小时后絮凝率只降低9.2％说明该絮凝剂对高温不敏感，热稳定性较强。絮凝剂对土壤悬浊液也具有良好的絮凝能力，絮凝率最高可达96.6％。另外对Aeromonas sp．N11所产的微生物絮凝剂进行了初提，得到其粗产品产量约为2.25g／L，产量相对较高。 对Aeromonas sp．N11所产絮凝剂的研究表明，该微生物絮凝剂在较宽的pH值和温度范围内，较低的投加量时仍然保持有较高的絮凝活性，显示出其具有良好的应用前景。更多还原

【Abstract】 Bioflocculants, having good flocculating activity, are the metabolic products of the microorganism, which are safe, non-toxic and can be biodegraded easily. Since they overcome the shortcomings in utilizing safety and environmental pollution of the inorganic flocculants and organic flocculants, research and exploration of bioflocculants is realistically significant and have wide prospect in application.This research screened 5 strains of bioflocculant-producing microorganisms from activated sludge from a municipal wastewater treatment plant in Changsha, soil sample from Yuelu Mountain and sludge beside Xiangjiang River by conventional methods. A strain with high flocculating activity was obtained after rescreening, which was identified as Aeromonas sp. and was named Aeromonas sp. N11. Taking the Aeromonas sp. N11 as the subject investigated, .the effect of the cultural conditions and the medium composition and proportion on bioflocculant production was studied, and the flocculating characteristic of the bioflocculant produced by strain Aeromonas sp. N11 was studied also.The experimental results showed that the medium composition and proportion had significant effect on bioflocculant production. After single factor experiment and orthogonal experiment it was found that: high C/N ratio was beneficial to bioflocculant production; carbon source sucrose was beneficial to bioflocculant production of Aeromonas sp. N11; the compound nitrogen source was better than the single nitrogen source; yeast extract was beneficial to bioflocculant production; NaCl could increase the flocculating activity of the bioflocculant produced; carbon source sucrose and nitrogen source carbamide had the maximun effect. The optimium component proportion of medium obtained according to the orthogonal experiment was: sucrose 20g/L, yeast extract 0.8g/L, carbamide 0.5g/L, (NH4)2SO4 0.5g/L, NaCl 7g/L. The optimiun cultural conditions was: pH 7, 30, 170r/min, cultivated for 72hours in flakes.The results of the experiment on the flocculating characteristic of the bioflocculant produced by strain Aeromonas sp. N11 showed that the flocculating activity of the bioflocculant was due to the secondary metabolic product of N11. The bioflocculant was present in the fermentation liquid mainly and had a high thermostability. Univalent ions and divalent ions could promote the flocculating effect while Fe3+ of high concentration restrained flocculation, in which K+, Na+, Ca2+ hadthe best effects. The best dosage of the bioflocculant and the coagulant aids was different for different substances to be flocculated. pH and temperature had effect on flocculating activity of the bioflocculant. The optimum pH had reference to the coagulant aids and the substances to be flocculated. The bioflocculant also had a good effect on soil suspension and the highest flocculating rate was 96.6%. The bioflocculant was simply purified and the producibility of the crude bioflocculant was 2.25g/L, which is relatively high.The study on the bioflocculant produced by Aeromonas sp. N11 showed that the bioflocculant could keep high flocculating activity in wide range of pH and temperature and in low dosage, which indicated a good utilization prospective of the bioflocculant.更多还原