一株耐Cd菌株的分离、鉴定及基本特性

Isolation, identification and characterization of a Cd resistant bacterium

摘要:

[目的]从活性污泥中筛选耐镉（Cd）菌株，并研究其生长特性及对溶液中Cd²⁺吸附的最佳条件，以期为重金属Cd污染水体的微生物修复提供菌株资源和应用技术参考。[方法]采用平板划线法，从活性污泥中分离、筛选、驯化出耐Cd菌株，通过16S rRNA基因序列分析及溶血试验、蛋白质毒素结晶试验进行初步鉴定，并采用单因素实验优化菌株的培养条件，通过正交实验确定菌粉吸附溶液中Cd²⁺的最佳条件，同时利用SEM-EDS及FTIR分析探讨菌粉吸附Cd²⁺的机理。[结果]经分离、驯化得到1株耐Cd细菌菌株，命名为H6，初步鉴定为蜡样芽孢杆菌（Bacillus cereus），最大Cd²⁺耐受浓度为350 mg/L。菌株H6的最佳生长条件为：pH 6.0-8.0，温度28℃，转速120-210 r/min，接种量1%-5%；菌株H6在生长过程中，培养液pH值先稍微下降然后不断上升。菌粉吸附Cd²⁺的正交优化条件为：菌粉用量0.125 g/L，吸附时间2 h，pH 5.0，温度30℃，此条件下吸附量为205 mg/g。SEM-EDS分析和红外光谱（FTIR）分析表明，在吸附过程中主要作用基团有羟基、羧基、羰基、酰胺基和烷基，此外，Ca²⁺与Cd²⁺发生了离子交换。[结论]从活性污泥中分离出的菌株H6，初步鉴定为蜡样芽孢杆菌（Bacillus cereus），是1株具有较强Cd²⁺吸附能力的细菌菌株。

Abstract:

[Objective] We isolated and identified a cadmium resistant bacterium from activated sludge. Furthermore, we studied its growth characteristics and optimal biosorption conditions of Cd²⁺. This study was expected to provide strain resources and applied reference for microbial remediation of cadmium contaminated water.[Methods] The bacterium was isolated by streak plate and identified based on its 16S rRNA analysis, hemolysis testing and protein crystallization dying experiment. The growth conditions of the strain were determined by single factor test. The optimal biosorption conditions of bacterial powder were investigated by designed orthogonal experiment. Besides, the biosorption mechanisms were discussed by Scanning electron microscope (SEM), Energy Dispersive X-ray Scanning (EDS) and Fourier transform-infrared spectroscopy (FTIR) analysis. [Results] The strain was identified as Bacillus cereus and named as H6. The maximum cadmium tolerance concentration of strain H6 was 350 mg/L. Its culture conditions were:initial pH 6.0 to 8.0 at 28℃, shaking speed of 120 to 210 r/min, inoculation 1% to 5%. During the growth of strain H6, the pH of culture medium first decreased slightly and then increased gradually. The optimal biosorption conditions of bacterial powder were:dosage of 0.125 g/L, contact time of 2 h, pH 5.0 and 30℃, the biosorption capacity reached 205 mg/g. SEM-EDS and FTIR results revealed that ion exchange between Ca²⁺and Cd²⁺ occurred and the functional group of hydroxyl, carboxyl, carbonyl, amido and alkyl played a principal role during the biosorption process. [Conclusion] Strain H6, isolated from the activated sludge, was identified as Bacillus cereus with good adsorption property for Cd²⁺.