镉抗性细菌的筛选及其生物矿化硫化镉去除溶液中的镉离子

Screening of Cd(Ⅱ)-resistant bacteria and its biomineralization of cadmium sulfide to remove cadmium ions in solution

水体重金属污染中,镉[Cd(Ⅱ)]因其高毒性成为最受关注的对象之一。生物矿化是通过生物作用影响金属形态,把有毒重金属转化为不相容的危害较小的化合物,成为环境污染治理领域的研究热点。本研究从重金属污染土壤中筛选出一株镉抗性细菌N1905,基于16S rRNA序列分析鉴定为Enterobacterludwigii N1905。研究其对多种重金属抗性和不同镉浓度下生长情况,结果表明菌株N1905具有多种重金属耐受性,在LB液体培养基中对Cd(Ⅱ)的最小抑制浓度(MIC)为8 mmol·L^(-1),高浓度的Cd(Ⅱ)抑制其生长代谢。同时研究发现,细菌N1905以L-半胱氨酸为特异性底物产硫化氢;在细菌N1905、1 mmol·L^(-1)硝酸镉和2 mmol·L^(-1) L-半胱氨酸共存培养过程中,通过细胞外沉淀硫化镉可以100%去除水溶液中的Cd(Ⅱ)。此外,细菌N1905对消除多种复杂水溶液中Cd(Ⅱ)污染有较好应用潜力。XRD、SEM-EDS及光谱学分析表明细菌N1905可生物合成具有光学特性的硫化镉纳米颗粒。

Cadmium in heavy metal-polluted water has attracted widespread attention because of its high toxicity.Biomineralization is the transformation of toxic heavy metals into incompatible and less harmful compounds through microbial metabolism processes;it has become a research hotspot in the field of environmental pollution prevention and control.In this study,a cadmium-resistant bacterium,N1905,was isolated from heavy metal-contaminated soil and identified as Enterobacter ludwigii N1905 based on 16S rRNA sequence analysis.Results showed that strain N1905 was tolerant to many heavy metal types.The minimum inhibitory concentration(MIC)of Cd(Ⅱ)in an LB liquid medium was 8 mmol·L^(-1),and the normal growth of strain N1905 was significantly inhibited under high concentrations of Cd(Ⅱ).Simultaneously,it was found that bacteria N1905 could produce hydrogen sulfide with L-cysteine as the specific substrate.In the co culture of strain N1905 with 1 mmol·L^(-1)cadmium nitrate and 2 mmol·L^(-1)L-cysteine,Cd(Ⅱ)ions in aqueous solution were approximately 100%removed by extracellular precipitation of cadmium sulfide.In addition,N1905 could efficiently remove cadmium ions from a variety of complex aqueous solutions.X-ray diffraction,scanning electron microscopy-energy dispersive spectroscopy,and spectroscopic analysis showed that the biosynthesized CdS was composed of nanoparticles with optical properties.