| 摘要: |
| 于1993年5月由南京大学藻类培养室提供极大螺旋藻藻种，用Zarrouk培养基培养后，用活藻体和甲醛杀死的藻体分别进行吸附实验；过滤出的藻体置于6×10-3 g/L左右浓度的Co2+，Ni2+，Cu2+，Zn2+离子混合液中。结果显示，死、活藻体都具有相似的吸附能力，对Co2+，Ni2+，Zn2+的富积大于203倍，对Cu2+的富积大于185倍；用热水提取、DEAE-纤维素D-23柱和Sephadex G-200柱纯化后，获得了纯细胞外壁多糖，其分子量为52kD。将该糖溶液盛在透析袋内，并置于4种离子混合液中进行吸附实验，结果显示，核糖对Co2+，Ni2+，Cu2+，Zn2+的富积倍数分别达1744，1644，1340，1750。藻体和多糖对Co2+，Ni2+，Zn2+的吸附都高于对Cu2+的吸附。比较藻体与多糖对4种离子的吸附结果可见，藻体对离子的吸附主要是多糖的作用；多糖的红外光谱显示，金属离子改变OH和CO-NH的吸收峰，表明这两种基团与金属离子发生了络合作用；对Cu2+的络合滴定测定表明，Cu2+与多糖的结合度为0.40。 |
| 关键词: 极大螺旋藻 多糖 重金属离子 吸附作用 |
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| STUDY ON MECHANISM OF HEAVY METAL ACCUMULATION IN SPIRULINA MAXIMA, CYANOPHYTA |
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LI Jian-hong,ZENG Zhao-qi,XUE Yu-ming,TAI Zi-hou
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1.Department of Biology, Nanjing Normal University, Nanjing, 210008;2.Department of Biological Science and Technology,Nanjing University, Nanjing, 210008;3.Statdkey Laboratory of Coordination Chemistry, Nanjing, 210008
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| Abstract: |
| The accumulation of heavy metals by an intact alga, Spirulina maxima, and its extracelullar polysaccharide (EPS) was studied The alga was supplied by Algae Culture Laboratory of Nanjing University in may 1995. The culture medium was Zarrouk medium. Living algae and dead algae killed by formol were obtained by filtration and mixed with a Co2+, Ni2+, Cu2+, Zn2+ complex solution (pH = 5.0), which was CoCl2, NiSO4, CuSO4, and ZnSO4 salts. Every metal ion content in the solution was around 6×10-3 g/L. After mixing with the metal ion solution for 30 min, the algae were filtered out and the concentrations of the four ions in the solution were measured. The results show that S. maxima strongly adsorb the four ions; the quantities of Co2+, Ni2+, Zn2+ adsorbed in the algae were more than 203 times higher than in the initial solution, with that of Cu2+ being more than 185 times. The abilities of the algae adsorpting Co2+, Ni2+, Zn2+ were higher than Cu2+. There is no significant differences between the living and the dead (Tab.l) EPS of S. maxima was extracted by hot water and separated by a DEAE-cellular D-23 column and s Sephadex G-200 column. Its molecular weight was 52kD, measured by high liquid chromatogram. To measure the ability of EPS adsorpting metal ions, an EPS solution placed in a dialyzer was put into Co2+, Ni2+, Cu2+, Zn2+ ions complex solution. Each of the four ions in the solution had a concentration of around 6×10-3 g/L. The results show that the EPS strongly adsorbs the ions; it concentrated Co2+, Ni2+, Cu2+, Zn2+ ions for 1774, 1644, 1340 and 1750 times respectively (Tab.2). The EPS and the intact algae adsorbed more Co2+, Ni2+, Zn2+ than Cu2+. Comparing the adsorption of intact algae with the EPS, it is suggested that the adsorption of intact algae is mainly caused by the adsorption of EPS.
Infrared spectra of EPS and the EPS combined with different metal ions show that metal ions can change the key vibration of OH (3422, 1416, l230) and CO-NH (1622) (Tab.3). Thus, the adsorption of metal ions by the EPS is due to OH and CO-NH coordinating the metals.
The capacity of EPS combining Cu2+ was measured using the method of ion-selective electrode. A curve of Cu2+ titrating EPS was obtained (Fig.1). At the equilibrium point, the titrate was 0.40. This observation means that each single sugar molecular of EPS can combine 0.40 molecular Cu2+. |
| Key words: Spirulina maxima, Polysaccharide, Heavy metal ions, Adsorption |
