【作者】 周娜；

【导师】 刘云国；

【作者基本信息】 湖南大学 ， 环境工程， 2008， 硕士

【摘要】 重金属的生物吸附是以吸附、离子交换、络合或微沉淀作用为基础的一种物理-化学现象,金属的生物吸附因其科学的新颖性和在环境保护中的应用潜力,一直受到极大的重视,许多研究表明,活的或死的、完整的微生物细胞以及微生物的代谢产物都能高效地吸附金属离子。目前关于死菌吸附重金属的研究已有很多报道,但是有关生长中的真菌对重金属吸附的报道很少。从湖南临乡桃林矿区土壤中分离到一株高抗铜和锌的菌株,经26S rRNA D1/D2鉴定为棘孢曲霉Aspergillus aculeatus。本实验将生长中的该菌体作为活性生物吸附剂,选择铜(Ⅱ)、锌(Ⅱ)两种离子作为吸附质。在单一重金属离子体系中,研究在不同溶液初始pH值、不同吸附质初始浓度、不同吸附时间情况下,菌体对铜(Ⅱ)、锌(Ⅱ)两种离子的吸附能力。根据实验结果确定真菌吸附的优化条件。不少重金属是微生物正常生长的必需元素,但是当重金属在菌体内浓度过高时,会对菌体产生毒性。微生物可通过细胞的表面富集与细胞膜成分的改变减小毒性的破坏,通过多途径的联合作用对重金属的毒性进行解毒。重金属的抗性增强了各种微生物在恶劣环境下的生存能力。本文研究了铜(Ⅱ)、锌(Ⅱ)两种离子对菌体的最低抑制浓度(MIC),并通过电镜照片和红外光谱图分析菌体吸附金属离子前后的变化。此外还通过碘量法测定不同培养环境中菌体内谷胱甘肽含量的变化,初步探究菌体产生金属抗性的机理。实验表明在优化条件下:30℃,pH值5.0,起始铜离子和锌离子浓度为50mg/L,摇床转速为120r/min,培养时间120h,该菌体对铜离子和锌离子的吸附率分别达到54%和60%。菌株可以单抗铜400mg/L、锌800mg/L。电镜照片表明25mg/L铜锌两种离子对菌体造成了一定程度的损伤,使其细胞表面形态和内部结构均发生了变化;红外光谱图说明菌体表面的-OH、磷酸酯、糖环等参与了吸附活动。A. aculeatus菌在重金属铜和锌胁迫下,体内的谷胱甘肽起了显著变化。在铜锌离子浓度为50mg/L时,菌体内谷胱甘肽的含量达到最大值,分别为0.98和0.88mg/g。而没有金属离子胁迫时生长的菌体体内谷胱甘肽含量很低,只有0.04mg/g。可以初步认为谷胱甘肽缓解了铜、锌离子对Aspergillus aculeatus的氧化损伤。更多还原

【Abstract】 The metal biosorption is a physico-chemical phenomenon based on absorption, ion exchange, complexation or microprecipitation. Biosorption of metals has been recently receiving a great deal of attention for both its scientific novelty and application potential in environmental protection or recovery of precious metals. Many investigations have showed that intact microbial cells, living or dead,and derived microbial products,can be highly efficient absorption of metal ions, especially from diluted external concentration. There have been a number of reports on the biosorption of heavy metals. However, there have been only a few reports on living epiphyte absorption.A stain of resistance to copper and zinc with high concentration was isolated from soil of tiaolin in HuNan province. With the identification of 26S rRNA D1/D2 gene sequence, the strain was identified as Aspergillus aculeatus. This experiment used the growing fungus as adsorbent, and Cu2+, Zn2+ as adsorate. The influences of experimental conditions such as time, pH value, temperature, inditial concentration of adsorbent and adsorate on adsorbing effect are studied.Many heavy metals are the necessary elements for the microorganisms. But when the concentrations of the intercellular heavy metals are too high, the metals become poisonous. The microorganisms can minish the destroy of the toxicity by alter the componential of the membrane and enhance the superficial enrichment. Metal-resistance of microorganisms may enhance their ability to live in bad surroundings.This text maked sure the Cu2+, Zn2+ to 2# fungus’minimal inhibitory concentration (MIC). Using the electron magnifier and FTIR technic analysed the normal and absorption metals’fungus. Furthermore, the meath of iodimetric estimation was used to analyse the contents of glutathione which were cultured in different mediums. Primery research the mechanism of Metal-resistance by fungus.Its optimum growth conditions were temperature 30℃, pH 5.0, initial concentration of Cu2+ and Zn2+ 50mg/L, rate of the shaker 120r/min, cultured time 120h, the adsorption efficiency could reach 54% and 60% respectively. It can resist copper of 400mg/L and zinc of 800mg/L. The electron magnifier photos show that fungus cells appeared different degree damnification under 25mg/L Cu2+, Zn2+. The results of FTIR show that the fungus surface’s–OH、phosphate、polyoses are absorption movement centers. Stress of Cu2+, Zn2+ induced fungus interior GSH’s change. Under the condition of 50 mg/L Cu2+, Zn2+, GSH achieved to the maximum, respectively 0.98 and 0.88mg/g. While GSH at normal fungus only was 0.04 mg/g. It can confer that glutathione seems to play a favorable role in avoidance of heavey metal oxidation stress from the results.更多还原