【作者】 樊霆；

【导师】 刘云国；

【作者基本信息】 湖南大学 ， 环境工程， 2009， 博士

【摘要】 重金属及其化合物在工业中被广泛应用,导致大量含重金属废水、废渣产生,对环境造成严重污染。在重金属污染治理中,如何降低或消除重金属的毒性是减小重金属污染危害的关键。自然界中许多菌种具有重金属抗性和富集能力,因而用微生物法治理重金属污染具有较好的前景。本文选用几株不同形式的真菌用于重金属离子的富集和吸附,分别对生长中的菌体对重金属的抗性机制、富集特性,活性菌体和非活性菌体的吸附特征和机理进行了详细研究与探讨。从湖南省岳阳市临乡铜锌尾砂坝的尾砂中分离筛选出一株对Cu(II)和Zn(II)具有高抗性的富集菌CTB430-1,通过细胞形态观察、ITS基因序列测定和系统发育分析,被鉴定为黄曲霉(Aspergillus flavus)。菌株CTB430-1对Cu(II)和Zn(II)具有较强的抗性,Cu(II)和Zn(II)对其最低抑菌浓度分别为400和800mg/L。选择的对比菌株黑曲霉(Aspergillus niger)的最低抑菌浓度分别为200和300mg/L,其对两种重金属的抗性相对较弱。CTB430-1对Cu(II)和Zn(II)的富集量分别在浓度为200和250mg/L时达到最大,为30.82和40.37mg/g。A. niger分别在150和250mg/L时达到最大,为8.89和22.80mg/g。对菌体CTB430-1和A. niger富集Cu(II)和Zn(II)的影响因素如溶液初始pH值、重金属初始浓度、共存离子、孢子液接种量、温度进行了研究。结果表明,溶液初始pH值对两个菌株的生长和富集量均有重要影响,pH≤2.0时抑制菌体的生长;随pH值在2.0-5.0范围内增加,菌体生长量和富集量均增加;在pH值为5.0时均达到最大。在Cu(II)和Zn(II)为25-100mg/L范围内,重金属浓度增加对菌体CTB430-1和A. niger生长的有潜在抑制作用,导致菌体生长延滞期增加,两种菌体生长量均在5d时达到平衡;两种菌体对不同浓度Cu(II)和Zn(II)富集均分别在4d和5d时达到平衡。在Cu(II)和Zn(II)共存系统内,除在Cu(II)+Zn(II)浓度为(25+25)mg/L和(25+50)mg/L时对A. niger菌体生长有较小的促进作用外,对两种菌体生长抑制作用均大于单离子系统,金属单离子浓度较高时,其竞争能力较强,富集能力相对较大。菌体CTB430-1和A. niger在Cu(II)和Zn(II)溶液的生长量和富集能力随接入的孢子液体积增加而增加,在体积为1mL时达到平衡。两菌体的生长量均在25℃-30℃之间达到最大,富集量在30℃-35℃之间达到最大。电镜扫描和透射分析CTB430-1和A. niger菌丝体富集Cu(II)和Zn(II)前后的表面特征和内部结构变化,表明菌体生长受重金属毒害作用可能破坏了菌体表面结构,或菌丝体表面可能吸附了部分重金属而使表面模糊;富集过程主要由表面吸附和胞内富集两部分组成。红外光谱分析表明菌体CTB430-1对Cu(II)的富集并未破坏其本身的结构,羟基是CTB430-1吸附或络合或螯合Cu(II)的主要活性基团,而A. niger吸附是由菌体中多糖类基团上的P作为配位原子与Cu(II)配位络合所造成。对CTB430-1和A. niger对Cu(II)和Zn(II)抗性机制进行研究。结果表明,高浓度的Cu(II)和Zn(II)显著抑制了CTB430-1和A. niger生长,导致可溶性蛋白含量下降,还原型谷胱甘肽(GSH)含量显著增加,说明GSH缓解了重金属对细胞的氧化损伤作用;且超氧化物岐化酶(SOD)和过氧化氢酶(CAT)活性随重金属浓度增加显著增加,这是两种菌体抵抗过氧化的主要表征之一,CTB430-1的酶活增加较大,说明CTB430-1对Cu(II)和Zn(II)的抗性较A. niger强。Cu(II)和Zn(II)作用时,可诱导CTB430-1和A. niger菌体丙二醛(MDA)含量增加,Cu(II)作用时显著增加,说明活性氧自由基介导的膜质过氧化作用是Cu(II)导致CTB430-1和A. niger细胞损伤的主要原因。就外源NO对Cu(II)作用下菌株CTB430-1和A. niger抗氧化系统的影响进行研究。结果表明,低浓度NO处理(0.1mmol/L的硝普钠(SNP)溶液)时,能促进CTB430-1和A. niger生长。外源NO可能通过减缓可溶性蛋白质的降低,促成GSH的合成,诱导菌体内SOD和CAT活性增强来增加菌株CTB430-1和A. niger的抗氧化能力。低浓度的NO可有效降低两菌体内MDA的含量来减缓Cu(II)的毒性,但高浓度NO(0.3mmol/L的SNP)的缓解作用不明显。对活性黑曲霉(Aspergillus niger)对Cd(II)和Zn(II)的吸附特征进行研究。结果表明,A. niger对Cd(II)和Zn(II)吸附的最佳pH值分别为4.0和6.0;其最佳吸附温度和转速范围分别在25-30℃和100-150r/min。在最佳条件下,吸附量在Cd(II)和Zn(II)的初始浓度分别为75和150mg/L达到最大,分别为17.35和24.60mg/g;A. niger对两种重金属的吸附均在24h达到平衡;对Cd(II)和Zn(II)吸附均符合Langmuir等温模型,吸附过程可由二级速率动力学方程描述。本文还对非活性简青霉(Penicillium simplicissimum)吸附Cd(II)、Zn(II)和Pb(II)的吸附等温线、动力学和热力学进行了研究,同时就溶液初始pH值、重金属初始浓度、吸附剂用量、吸附时间、温度和共存离子对吸附的影响进行了研究。结果表明,P. simplicissimum对Cd(II)、Zn(II)和Pb(II)吸附均符合R-P等温模型,D-R方程的平均自由E值说明了吸附过程可能存在化学离子交换;不同温度条件下的吸附动力学可由准二级速率方程描述;吸附热力学常数ΔG o、ΔHo和ΔS o数值表明该吸附反应是自发过程,吸热反应。更多还原

【Abstract】 Heavy metal and its compounds are widely used in many industries and a large quantity of containing heavy metals wastes are released into environment. Heavy metal has posed great threat on environmental safety and human health. The reduction and removal of heavy metal is the key for the detoxification of heavy metal. Many tolerance strains have been found to be able to bioaccumulation of heavy metal and bioremediation has been regarded as a promising approach for the treatment of heavy matal pollution. In this paper, different fungal strains were applied to the biosorption and bioaccumulation of heavy metals. The resistence mechanisms, bioaccumulation characteristics of heavy metal by growing cells, and the biosorption characteristics and mechanisms by living and dead cells were studied in detail.A novel fungus CTB430-1 with resistance to copper and zinc was isolated from soil at a copper and zinc Tailing of Linxiang in Yueyang city, Hunan province. The fungus was identified as Aspergillus flavus by analyzing the morphology and measuring the ITS sequence.The minimal inhibitory concentration of the strain CTB430-1 for Cu(II)and Zn(II) were 400 and 800mg/L, respectively. Compared with CTB430-1, the minimal inhibitory concentration of Aspergillus niger which was contrastive stain in our study were only 200 and 300 mg/L. So the tolerance of CTB430-1 was high. The maximum bioaccumulation capacities of Cu(II)and Zn(II) by CTB430-1 were 30.82 and 40.37 mg/g at initial concentrations of 200 and 250 mg/L, and that of A.niger were 8.89 and 22.80 mg/g at initial concentrations of 150 and 250 mg/L, respectively.The factors that affected the bioaccumulation efficiency by isolated strain CTB430-1 and contrastive stain A. niger, were thoroughly investigated, such as initial pH value of liquid medium, initial Cu(II)and Zn(II) ions concentration, co-ions in the liquid medium, spores inoculum amount and temperature.The results showed that the initial pH value of liquid medium had important effect on growth and bioaccumulation of CTB430-1 and A. niger, at low pH value(≤2.0), the growth was inhibited when the initial. With the pH value increased, the growth and bioaccumulation capacity by the two strains increased with increasing pH value in the range of 2.0-5.0 for Cu(II)and Zn(II), and the maximum growth and bioaccumulation capacity were hold at pH 5.0. The potential inhibition on growth of CTB430-1 and A. niger were increase by increasing intial concentration of Cu(II) and Zn(II) in range of 25-100mg/L, and the growing period were delay,all the stains reached the growth balance in 5d. The bioaccumulation amount of Cu(II) and Zn(II) ions increases by CTB430-1 and A. niger with the increasing initial metal ion concentration and contact time. The bioaccumulation equilibriums of Cu(II) and Zn(II) by CTB430-1 reached in 4d, which of A.niger reached in 5d.In the binary Cu(II)+Zn(II) system, the presence Cu(II)/Zn(II) ions induced to the inhibition in the growth of CTB430-1 and A. niger except that the concentration of (25+25) and (25+50)mg/L could promote little the growth of A. niger. When the concentration of Cu(II)/Zn(II) ions was high, the competition and bioaccumulation ability of Cu(II)/Zn(II) ions were strong. With the spores inoculum amount increased, the growth and bioaccumulation of CTB430-1 and A. niger were increase, and reached balance at 1mL of the inoculum amount. Maximum growth and bioaccumulation capacities were obtained at different temperatures in the range of 25-30℃and 30-35℃, respectively.The changes of micrographs obtained from scanning electron micrograph and transmission electron microscope of CTB430-1 and A. niger before and after Cu(II) and Zn (II) accumulation showed that all the stain suffered the heavy metal toxicity in the growing process, which could destroy the surface structure possibly or some heavy metal ions maybe were uptaked on the surface of mycelium that made the surface become blurry. The bioaccumulation included mostly extracellular and intracellular biosorption. The results of FTIR spectrum showed that the Cu(II) ions counld not destroy the structure of CTB430-1 in the process of bioaccumulation, hydroxyl was the primary activity groups in the biosorption or complexing/chelated Cu(II) ions. However, the biosorption of Cu(II) ions by A.niger were made metal-ligand complexes by the phosphorus as donor atoms which in polyoses groups.The resistant mechanism of Cu(II) and Zn(II) by CTB430-1 and A. niger were studied. It was observed that high concentration of Cu(II) and Zn(II) could restrict the growth of CTB430-1 and A. niger obviously, cause decrease the soluble protein content and increase in GSH levels, which could alleviate the oxidation stress of Cu(II) and Zn(II). The activities of SOD and CAT in cells of CTB430-1 and A. niger increased obviously with the concentration of Cu(II) and Zn(II) increasing, which was one of the attributes of two stains’resisting peroxidation. The enzyme activities of CTB430-1 increased highly, so the resistance to Cu(II) and Zn(II) of CTB430-1 were stronger than A.niger. The MDA levels enhanced in the cells of CTB430-1 and A. niger under the stress of Cu(II) and Zn(II), but the chang were prominent of all the stains under the stress of Cu(II). It showed that the mechanisms for Cu(II) to damage CTB430-1 and A. niger by in ducing ROS and lipid peroxidation.The effects of exogenous nitric oxide (NO) on antioxidation system of CTB430-1 and A. niger under the stress of Cu(II) were explored, the result indicated that the pretreatment of sodium nitroprusside (SNP), a NO donor, at 0.1nmol/L could increase the growth of two stains, and alleviate the reduction of soluble protein, induce the creation of GSH, and enhance the activities of SOD and CAT, all of that could enhance the capacity of antioxidation for CTB430-1 and A. niger. At the same time, the NO (0.1mmol/L SNP) reduced the toxicy of Cu(II) by decreasing the MDA amount in cells of CTB430-1 and A. niger. However, the alleviations of high NO concentration (0.3mmol/L SNP) were not obvious.The biosorption characteristics of Cd(II) and Zn(II) by living A. niger were investigated. The optimum adsorption pH value for Cd(II) and Zn(II) were 4.0 and 6.0. The best temperature and agitation rate were in the range of 25-30℃and 120r/min for all metal ions. Under the optimal conditions, the maximum uptake capacities of Cd(II) and Zn(II) ionsare 15.50 and 23.70 mg/g at initial concentrations of 75 and 150 mg/L, respectively. Biosorption equilibrium isestablished within 24h for Cd(II) and Zn(II) ions. The adsorption data provide an excellent fit to Langmuir isotherm model. The results of the kinetic studies show that the rate of adsorption follows the pseudo-second order kinetics.The isotherms, kinetics and thermodynamics of Cd(II), Zn(II) and Pb(II) biosorption by non-living Penicillium simplicissimum were also investigated in a batch system. The effects of pH, initial metal ions concentration, biomass dose, contact time, temperature and co-ions on the biosorption were studied. Adsorption data were well described by the Redlich-Peterson model. Chemical ion-exchange was found to be an important process based on free energy value from Dubini-Radushkevich isotherm for all metal ions. The results of the kinetic studies of all metal ions at different temperature showed that the rate of adsorption followed the pseudo second-order kinetics well. The thermodynamics constantsΔG o,ΔH oandΔS oof the adsorption process showed that biosorption of Cd(II), Zn(II) and Pb(II) ions on Penicillium simplicissimum were endothermic and spontaneous.更多还原