重金属镉胁迫下胞外聚合物在小球藻脱氮除磷过程中的作用

发布时间：2018-03-05 13:49

本文选题：胞外聚合物　切入点：脱氮除磷　出处：《湘潭大学》2015年硕士论文　论文类型：学位论文

【摘要】：基于藻类的生物膜技术具有脱氮除磷的优势,在城镇污水处理中具有应用前景,但污水中的重金属等毒物可影响藻细胞及其胞外聚合物(EPS)。EPS是藻类等生物在特定环境下产生的高分子物质,具有多种生物作用,而目前对于EPS在重金属胁迫藻类脱氮除磷过程的作用及机制尚不明晰。本文以小球藻(Chlorella vulgaris)为研究目标,以镉为重金属代表,在考察镉胁迫对小球藻脱氮除磷效率影响的基础上,探明镉胁迫下氮、磷、镉在EPS及藻细胞内的分布;明确镉胁迫下EPS的产生特性及其与脱氮除磷效率之间的关系。论文主要得到了以下的研究结论:(1)Cd2+对小球藻生长具有较强的毒性效应,其96h-EC50值为1.17 mg/L。低浓度的Cd2+(0.1 mg/L)能促进小球藻的生长、酯酶活性和脱氮除磷效率,而高浓度的Cd2+(0.5 mg/L)则会产生抑制效应。Cd2+浓度为1.0 mg/L时,6天实验周期中小球藻的平均生长速率是3.29×105 cells/(mL*d),为无Cd2+对照组的59.4%。在1.0mg/L Cd2+胁迫下,小球藻对氨氮(NH4+-N)和正磷酸盐(PO43--P)去除率仍然能保持在对照组(分别为68.0%和50.5%)的62.6%和64.9%,单个藻细胞对NH4+-N和PO43--P的去除量也能保持在对照组的69.3%和62.5%。酯酶活性的实验结果表明,EPS对Cd2+胁迫小球藻脱氮除磷中具有缓解毒性作用。(2)在1.0 mg/L Cd2+胁迫下,溶解态EPS(S-EPS)中总氮(TN)和总磷(TP)的含量分别减少至6.15 mg/L和1.44 mg/L,相比于对照组增加了56.8%和30.7%;结合态EPS(B-EPS)中TN和TP的平均含量分别为0.27 mg/L和0.18mg/L,比对照组高26.8%和27.5%;处理组中单个藻细胞内TN和TP的含量增加至1.39×10-6 mg/L和0.20×10-6 mg/L,为对照组的82.5%和79.9%。Cd2+在EPS及细胞内的分布表明,EPS(尤其是B-EPS)可作为细胞的防护栏障阻止Cd2+进入细胞。在1.0 mg/L Cd2+胁迫下,55.4%的Cd2+分布在B-EPS中,仅有19.5%分布在S-EPS中。此外,Cd2+胁迫减慢了EPS中氮、磷的扩散速率以及藻细胞对氮、磷的吸收速率,但NH4+-N和PO43--P扩散的平均速率仍然分别保持为对照组的65.8%和64.1%;藻细胞对NH4+-N和PO43--P的吸收速率也能保持在对照组的62.0%和56.2%。(3)1.0 mg/L Cd2+胁迫加速了EPS的产生,实验周期中第6天时S-EPS含量达到15.56×10-7μg/cell,平均B-EPS含量为4.38×10-7μg/cell,比对照组分别增多了20.0%,30.4%。同时,S-EPS中多糖和蛋白质分别达到9.74×10-7和7.53×10-7μg/cell,比对照组增多了17.5%和19.3%;B-EPS中多糖和蛋白质平均含量分别为5.45×10-7和3.17×10-7μg/cell,较对照组增加20.3%和33.2%。三维荧光光谱(3D-EEM)表明,S-EPS中含有类色氨酸和类腐殖酸,B-EPS含有类酪氨酸和类色氨酸。Cd2+胁迫下EPS中各组分含量相比于对照组都有所增加,且S-EPS中的类色氨酸和B-EPS中的类酪氨酸峰位置发生了红移现象。傅里叶红外转换光谱(FTIR)结果表明,与Cd2+相互结合的主要官能团是S-EPS和B-EPS中的-OH或-NH(3446-3460 cm-1)、蛋白质中的C=O(-1642 cm-1),以及S-EPS中多糖上的C-O-C或C-O(-1081 cm-1),且出现了新的官能团,如属于蛋白质的-NH(1558,1540 cm-1)和C=O(1384 cm-1),说明EPS中的蛋白质和多糖是与Cd2+作用的主要成分。在1.0 mg/L Cd2+胁迫下,EPS的产生总量与小球藻脱氮除磷效率之间呈现出良好的正相关性,其R2值分别为0.9905(NH4+-N)和0.9414(PO43--P)。相比于PO43--P,EPS含量与NH4+-N去除率之间线性关系更为明显。
[Abstract]:Biofilm technology of algae with nitrogen and phosphorus removal based on the advantages of application in urban sewage treatment, but the sewage in the heavy metal poison can affect algal cells and extracellular polymers (EPS).EPS is a polymer material such as algae organisms in a particular environment, with a variety of biological effects, but the effect and the mechanism of EPS in heavy metal stress algal nitrogen and phosphorus removal process is still not clear. In this paper, Chlorella (Chlorella vulgaris) as the research object, with the heavy metal cadmium as representative, in the study of cadmium based efficiency of nitrogen and phosphorus removal effect of Chlorella, proven under Cadmium Stress of nitrogen, phosphorus, and distribution of cadmium in EPS in algae cell the relationship between characteristics; clear under cadmium stress EPS and nitrogen and phosphorus removal efficiency. The thesis obtained the following conclusions: (1) Cd2+ has strong toxic effects on the growth of Chlorella vulgaris, 96h-EC The 50 value is 1.17 mg/L. and low concentration of Cd2+ (0.1 mg/L) can promote the growth of Chlorella, esterase activity and nitrogen and phosphorus removal efficiency, and high concentration of Cd2+ (0.5 mg/L) will have the inhibitory effect of.Cd2+ concentration was 1 mg/L, the average growth rate of the 6 day experimental period of C.pyrenoidosa is 3.29 x 105 (cells/ mL*d), no Cd2+ control group 59.4%. in 1.0mg/L under the stress of Cd2+, Chlorella vulgaris (NH4+-N) on ammonia nitrogen and orthophosphate (PO43--P) removal rate remained in the control group (68% and 50.5%) of 62.6% and 64.9%, the experimental results of single algae cell removal on NH4+-N and PO43--P can maintain 69.3% 62.5%. and esterase activity in the control group showed that EPS and Cd2+ stress on nitrogen and phosphorus removal can alleviate the toxic effect of Chlorella. (2) at 1 mg/L under the stress of Cd2+, dissolved EPS (S-EPS) in total nitrogen (TN) and total phosphorus (TP) content decreased to 6.15 mg/L and 1.44 mg/L respectively, phase Than in the control group increased by 56.8% and 30.7%; bound EPS (B-EPS) TN and TP in the average content of mg/L and 0.18mg/L were 0.27, 26.8% higher than the control group and the treatment group was 27.5%; in the individual algal cells within TN and TP increased to 1.39 * 10-6 * 10-6 mg/L and 0.20 mg/L distribution the control group 82.5% and 79.9%.Cd2+ in EPS cells and that EPS (especially B-EPS) can be used as a protective barrier to prevent Cd2+ cells into cells. In 1 mg/L Cd2+ under the stress of 55.4% Cd2+ distribution in B-EPS, only 19.5% of the distribution in S-EPS. In addition, Cd2+ stress slows down the EPS in nitrogen. The diffusion rate of nitrogen and phosphorus and algal cells, the absorption rate of phosphorus, but the average rate of NH4+-N and PO43--P diffusion are still maintained as the control group 65.8% and 64.1%; the absorption rate of algae cells to NH4+-N and PO43--P can be maintained at 62% in the control group and 56.2%. (3) 1 mg/L Cd2+ stress accelerated The production of EPS in the sixth day experimental period, the content of S-EPS was 15.56 * 10-7 g/cell, the average content of B-EPS is 4.38 x 10-7 g/cell, than in the control group were increased by 20%, 30.4%. and S-EPS in protein and polysaccharide were up to 9.74 x 10-7 and 7.53 x 10-7 g/cell more than that of control group. 17.5% and 19.3%; the average B-EPS content of polysaccharide and protein were 5.45 * 10-7 and 3.17 * 10-7 g/cell, increased 20.3% than that in control group and three dimensional fluorescence spectra of 33.2%. (3D-EEM) showed that S-EPS contains tryptophan like and humic acid, B-EPS containing tyrosine and tryptophan were under.Cd2+ stress EPS content compared with the control group increased, and the peak position of tyrosine in S-EPS tryptophan and B-EPS in the red shift phenomenon. Fourier transform infrared spectroscopy (FTIR) results show that the main functional groups combined with Cd2+ and B-EPS in S-EPS -OH or -NH (3446-3460 cm-1), C=O (-1642 cm-1 protein), and S-EPS polysaccharide on C-O-C or C-O (-1081 cm-1), and the emergence of new functional groups, such as belonging to protein -NH (15581540 cm-1) and C=O (1384 cm-1), EPS in protein and polysaccharide the main component of the interaction between Cd2+ and mg/L in 1. Under the stress of Cd2+, EPS between the total nitrogen and phosphorus removal efficiency of Chlorella showed a good positive correlation, the R2 values were 0.9905 (NH4+-N) and 0.9414 (PO43--P). Compared with PO43--P, the linear relationship between EPS content and NH4+-N removal rate is more obvious.

【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X703;X173

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