【作者】 陈宇华；

【导师】 魏群； 马湘蒙；

【作者基本信息】 广西大学 ， 环境科学与工程， 2021， 硕士

【摘要】 微藻凭借其对重金属有着良好的去除效果和耐受能力受到了广泛的关注。因此,探究重金属胁迫对微藻生理响应和抗氧化防御机制的影响至关重要。本文首先研究了镉胁迫对微藻生理活性的影响,并通过综合性分析优选出对镉耐受性强、去除效果好的藻种;然后在镉胁迫下对该藻种的抗氧化防御机制进行研究;此外,引入K3载体,进一步提升微藻对镉的去除效果和耐受能力;最后对镉胁迫前后的微藻细胞进行表征分析,阐明微藻对镉的去除机理及其解毒机制。本文的主要结论如下:(1)镉胁迫对微藻的生理活性产生了不利的影响。镉对蛋白核小球藻和斜生栅藻生物量的抑制作用较小,实验组的生物量与对照组相比仅减少了2.40%和1.56%;镉胁迫对斜生栅藻叶绿素a和硝酸还原酶(NR)的不利影响最小,实验结束时,实验组斜生栅藻叶绿素a的平均含量比初始值高13.54%,15 mg/L实验组斜生栅藻的NR含量比同期对照组低27.06%;此外,斜生栅藻对镉离子的平均去除率达到了85.20%,分别比蛋白核小球藻、铜绿微囊藻和小环藻高31.68%、13.77%和21.39%;综合性分析结果表明,斜生栅藻更适合应用于含镉废水处理。(2)镉胁迫使得斜生栅藻的抗氧化水平升高。含镉实验组的总抗氧化能力(T-AOC)、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)和谷胱甘肽(GSH)的平均活性或含量与对照组相比分别提高了17.71%、27.37%、4.05%、16.17%和34.27%,这是微藻抗氧化防御机制发挥作用的重要体现。(3)斜生栅藻生物膜对镉的去除效果和耐受能力优于悬浮的斜生栅藻。斜生栅藻生物膜对镉的平均去除率比悬浮的斜生栅藻高3.61%,胞外聚合物(EPS)的平均含量也高了40.45%;在20 mg/L镉浓度下胁迫72 h后,悬浮的斜生栅藻叶绿素a和叶绿素b的含量仅为对照组的42.79%和58.54%,斜生栅藻生物膜则为52.77%和83.09%;10 mg/L实验组斜生栅藻生物膜SOD的平均活性与悬浮的斜生栅藻相比提高了18.30%,GSH的平均含量也提高了35.73%。(4)表征分析阐明了斜生栅藻对镉的去除机理及其解毒机制。扫描电镜(SEM)图像显示镉的毒害会导致斜生栅藻的表面形态结构发生变化;傅里叶变换红外光谱(FT-IR)的结果说明斜生栅藻藻细胞表面的C-H、C=O、-OH或N-H酰胺I等官能团参与了斜生栅藻对镉离子的吸附;X射线光电子能谱(XPS)显示斜生栅藻藻细胞表面的C-C,C-H、C-O,C-N、C=O,O-C-O、O-H等化学键与镉离子发生了络合;X射线衍射(XRD)数据分析表明,斜生栅藻处理镉后,结晶度发生了明显的变化。更多还原

【Abstract】 Microalgae has received extensive attention due to its effective removal effect and tolerance to heavy metals.Therefore,it is very important to explore the influence of heavy metal stress on the physiological response and antioxidant defense mechanism of microalgae.This article first studied the effect of cadmium stress on the physiological activity of microalgae,and selected algae species with strong cadmium tolerance and good removal effect through comprehensive analysis.Then under the cadmium stress,the antioxidant defense mechanism of this algae was studied.In addition,the introduction of K3 carrier further improves the removal effect and tolerance of microalgae to cadmium.Finally,the microalgae cells before and after cadmium stress were characterized and analyzed to clarify the mechanism of microalgae’s removal of cadmium and its detoxification mechanism.The main conclusions of this article are as follows:(1)Cadmium stress has an adverse result on the physiological activity of microalgae.The inhibitory effect of cadmium on the biomass of Chlorella pyrenoidosa and Scenedesmus obliquus(S.obliquus)was relatively small,and the biomass of the experimental group was only reduced by 2.40% and 1.56%compared with the control group.Cadmium stress has the least adverse result on the chlorophyll a and nitrate reductase(NR)of S.obliquus,at the end of the experiment,the average content of chlorophyll a of S.obliquus in the experimental group was 13.54% higher than the initial value,and the NR content of S.obliquus in the 15 mg/L experimental group was 27.06% lower than that in the control group during the same period.Furthermore,the average removal rate of cadmium(II)by S.obliquus reached 85.20%,which was 31.68%,13.77% and 21.39% higher than that of Chlorella pyrenoidosa,Microcystis aeruginosa and Cyclotella hebeiana respectively.Comprehensive analysis results show that S.obliquus is more suitable for the treatment of cadmium-containing wastewater.(2)Cadmium stress increases the antioxidant level of S.obliquus.The average activity or content of total antioxidant capacity(T-AOC),superoxide dismutase(SOD),catalase(CAT),peroxidase(POD)and glutathione(GSH)of the cadmium-containing experimental group increased by 17.71%,27.37%,4.05%,16.17% and 34.27% respectively compared with the control group,this is an important manifestation of the role of the antioxidant defense mechanism of microalgae.(3)The removal effect and tolerance of S.obliquus biofilm to cadmium are better than those of suspended S.obliquus.The average removal rate of cadmium by S.obliquus biofilm is 3.61% higher than that of suspended S.obliquus,and the average content of extracellular polymeric substances(EPS)is also 40.45% higher.After 72 hours of stress at a concentration of 20 mg/L cadmium,the contents of suspended S.obliquus chlorophyll a and chlorophyll b were only 42.79% and 58.54% of those in the control group,while the S.obliquus biofilms were 52.77% and 83.09%.Compared with the suspended S.obliquus,the S.obliquus biofilm SOD average activity of the 10 mg/L experimental group increased by 18.30%,and the GSH average content also increased by 35.73%.(4)Characterization analysis clarified the removal mechanism and detoxification mechanism of S.obliquus to cadmium.Scanning electron microscopy(SEM)images show that cadmium poisoning can cause changes in the surface morphology and structure of S.obliquus.Fourier transform infrared spectroscopy(FT-IR)results indicate that C-H,C=O,-OH or N-H amide I and other functional groups on the surface of S.obliquus were involved in the adsorption of cadmium(II)on the surface of S.obliquus.X-ray photoelectron spectroscopy(XPS)showed that C-C,C-H,C-O,C-N,C=O,O-C-O,O-H and other chemical bonds on the surface of S.obliquus were complexed with cadmium(II).X-ray diffraction(XRD)data analysis showed that the crystallinity of S.obliquus treated with cadmium changed significantly.更多还原