【作者】 张娟；

【导师】 包木太；

【作者基本信息】 中国海洋大学 ， 应用化学， 2011， 硕士

【摘要】 随着工业的发展,大量重金属进入沉积物中,严重危害水生生物的生长,并通过生物富集、食物链放大等过程,进一步影响陆地物种和人类,给国家的经济造成了重大危害。近年来,重金属修复方法得到广泛研究。常采用的重金属修复方法主要有物理修复、化学修复和生物修复方法。物理修复工程量大,耗材耗力,而且很难将沉积物处理到要求值;化学修复会造成二次污染,因此都不是理想的重金属修复方法。生物表面活性剂是微生物在一定条件下产生的集亲水性和亲油性于一体的代谢产物。生物表面活性剂具有无毒、易生物降解等环境友好性,因而十分适合修复重金属污染。本文首先介绍了沉积物中重金属污染现状,主要修复方法及生物表面活性剂的应用;实验是以油田污水所筛选的高产生物表面活性剂菌株为实验对象,通过单因素分析方法确定了菌株的最佳发酵条件并提取生物表面活性剂;采用多种方法鉴定生物表面活性剂的结构,确定其为糖脂类生物表面活性剂;最后重点考察了在各条件下,生物表面活性剂对沉积物中重金属及其各形态的去除效果并探讨了生物表面活性剂与重金属作用的机理。所得结论如下:（1）菌株B-1为混合菌株,经分离得到两株菌,分别为Bbai-1和Bru-1。通过菌的生理生化特性试验及16S rDNA对菌株进行鉴定,初步确定Bbai-1为负短短芽孢杆菌属,Bru-1为泛生菌属。（2）通过实验得到该菌的最佳发酵条件。培养基组成:花生油40 g/L;尿素5 g/L;K2HPO4 3 g/L;NaCl 5 g/L;pH值为7。培养条件:温度为25℃,转速为150 r/min。（3）B-1所产表面活性剂是一种糖脂类的生物表面活性剂,产量为0.6-0.7 g/L,临界胶束浓度为175 mg/L,对温度、pH值及盐度具有较好的稳定性。与合成表面活性剂相比,生物表面活性剂的乳化能力保持时间更长,具有更好的稳定性。（4）与化学合成表面活性剂相比,生物表面活性剂能有效去除沉积物中的铅。生物表面活性剂溶液的浓度及pH值对铅的去除率影响较大。在pH值为9时铅的去除效果最好,去除率为50.7%。加入低浓度的阳离子可以促进铅的去除,当加入浓度为10 mmol/L的NaNO₃,铅的去除率为46.6%。增加淋洗次数及时间有助于铅的去除,但是考虑到应用的经济性最佳淋洗时间为60 h。生物表面活性剂对天然沉积物中铅的去除率低于人为污染沉积物的去除率,为38.0%。对于铅的不同存在形态,生物表面活性剂对可交换态、碳酸盐结合态及Fe-Mn氧化态有较好的去除效果。（5）淋洗前后沉积物的红外光谱对照可知,生物表面活性剂可能是通过改变沉积物的表面性质,从而将重金属由沉积物上解析下来。更多还原

【Abstract】 With the development of industry, a mass of heavy metals are released into sediment. Contamination in sediment can endanger the growth of aquatic organism, and then harm land species and humans through bioconcentration and food chain amplifying function. It is promising to remove heavy metal from sediment because of its toxicity. In recent years, remediation methods to heavy metals were widely studied. There are three main methods to remediate heavy metal pollution, including physical method, chemical method and bioremediation method. The disadvantage of physical method is consumable, and physical method can’t remove heavy metals to background value. Chemical method can induce secondary pollution. So physical method and chemical method are not ideal remediation to heavy metals. Biosurfactants are amphiphilic molecules with both hydrophilic and hydrophobic portions which are produced by microorganism. Biosurfactant applications in environmental industries are promising due to their biodegradability, low toxicity and effectiveness in enhancing the biodegradation and solubilization of low solubility compounds.Summarization of the thesis introduced the situation of heavy metal pollution in sediment, main removal heavy metal methods and the applications of biosurfactant. In this study, bacteria B-1 isolated from oily-waste water is object of this study. The best fermentation condition was determined by one-variable-at-a-time method, and obtained large yield biosurfactant at that condition. Biosurfactant was extracted and analysed its structure by thin layer chromatography and Fourier transform infrared. The result suggested that biosurfactant produced by bacteria B-1 was glycolipid. At last, Pb removal efficiency by biosurfactant at difference conditions was tested. The conclusions are as follows:(1) Two strains were isolated from bacteria B-1, named Bbai-1 and Bru-1. Bbai-1 and Bru-1 were identified as Brevibacillus parabrevis and Pantoea agglomerans respectively by biochemical and physiological characteristics, morphological and 16S rDNA.(2) The study of B-1 fermentation determined the optimal substrate component was (in gram per liter of water): peanut oil 40 g/L; urea 5 g/L; K2HPO4 3 g/L; NaCl 5 g/L; pH 7.0. And the B-1 was cultured in a gyratory shaker at 150 r/min at 25℃.(3) A biosurfactant with a low critical micelle concentration, CMC (175 mg/L), was produced by B-1 strain. The yields of crude biosurfactant were 0.6-0.7 g. Measurements of surface tention showed a high level of tolerance to temperature, pH and salinity of the product.(4) Compared to synthesized surfactant SDS, biosurfactant removed heavy metal more effective. 14.6% lead could be removed by SDS solution, while biosurfatant can remove 25.3% lead at the concentration lower than SDS concentration. The concentration and pH of biosurfactant solution can influence removal efficiency of Pb at a large degree. Removal efficiency of Pb could be enhanced with the increase of the biosurfactant concentrations, and could finally reach 25.3%. The best remediation was got when the pH of biosurfactant was 9, and 50.7% lead was removed at the condition. The ionic strength had a slightly influence on the removal of lead. Removal efficiency of Pb increased to 46.6% when adding 10 mmol/L NaNO3 to biosurfacment solution. With increasing the concentration of NaNO3, the effect of Pb removal decreased. With increasing washing time and times, removal efficiency of Pb was improved. Considering application economy, 60 h was determined as the optimal washing time. Lead in inartificial polluted sediment was more difficult to remove than it in artifical polluted sediment by biosurfactant. Comparing the spices transformation of lead before and after remediation in the sediment by Tessier method, it was evident that soluble species, carbonated fractions and iron-manganese oxides bound of Pb adsorb on the sediment were wiped off effectively.(5) Fourier transform infrared illustrated that biosurfactants change sediment surface properties, and cause heavy metals desorption from sediment.更多还原