克雷伯氏菌CW-D3T菌株硫酸盐厌氧呼吸对水中PHE-Cd2+的修复特性

Bioremediation characteristics of PHE-Cd2+ in water by anaerobic respiration of the sulfate-reducing bacterium Klebsiella sp. CW-D3T

摘要:

【目的】针对菲(phenanthrene, PHE)-Cd²⁺污染体系，探究一株兼性厌氧克雷伯氏菌属(Klebsiella sp.) CW-D3T菌株利用硫酸盐作为末端电子受体厌氧呼吸耦合降解目标污染物，解析硫酸盐还原体系中该菌株对不同Cd²⁺赋存浓度的响应机制以及PHE的厌氧代谢途径。【方法】构建硫酸盐初始浓度为20 mmol/L的还原反应体系，以促进功能菌的生长代谢活性并强化修复PHE-Cd²⁺污染；分析胞外聚合物分泌量变化以及特征峰的振动特征，探讨体系中Cd²⁺梯度浓度胁迫时细胞自身的响应行为；借助GC-MS和HPLC对硫酸盐还原体系中PHE的代谢产物进行定性和定量分析。【结果】Cd²⁺胁迫浓度为0.5−50 mg/L条件下，Klebsiella sp. CW-D3T菌株的硫酸盐厌氧还原体系可以良好强化去除目标化合物；Cd²⁺胁迫浓度不高于10 mg/L时，PHE和Cd²⁺去除率均高于70.00%。随着Cd²⁺胁迫浓度的增加，胞外聚合物(extracellular polymeric substances, EPS)中胞外多糖分泌含量较胞外蛋白更高，菌体细胞表面的多糖和蛋白骨架官能团特征峰的谱峰强度增强。Cd²⁺胁迫下PHE在硫酸盐还原体系中初始活化步骤更倾向于羧基化产生2-菲甲酸，初始Cd²⁺浓度分别为10 mg/L和50 mg/L时，2-菲甲酸含量在第5天均达到峰值(15.56μg/L和10.23 μg/L)，与未添加Cd²⁺对照组相比分别降低了27.56%和52.37%，Cd²⁺胁迫浓度对周期内与周期末2-菲甲酸含量具有显著影响。【结论】利用硫酸盐作为电子受体显著促进Cd²⁺赋存下Klebsiella sp. CW-D3T菌株对PHE的生物降解，胞外多糖和蛋白的解毒调控机制对提高微生物抗Cd²⁺胁迫具有积极作用。

Abstract:

[Objective] A facultative anaerobic bacterium Klebsiella sp. CW-D3T utilizing sulfate as the terminal electron acceptor for anaerobic respiration was used for degradation of target pollutants in the system with phenanthrene (PHE)-Cd²⁺ co-contamination. The response mechanism of the strain to different Cd²⁺ concentrations in the sulfate reduction system and the anaerobic metabolic pathways of the strain for degrading PHE were studied. [Methods] A sulfate reduction system with an initial sulfate concentration of 20 mmol/L was developed to enhance the growth and metabolic activity of functional bacteria and improve the bacterial performance for remediating PHE-Cd²⁺ co-contamination. The changes in extracellular polymer secretion and the vibrational characteristics of characteristic peaks were analyzed to explore the cellular responses to different Cd²⁺ concentrations. Furthermore, qualitative and quantitative analyses of the metabolic products of PHE in the sulfate reduction system were conducted by GC-MS and HPLC. [Results] In the presence of 0.5–50.0 mg/L Cd²⁺, the sulfate reduction system of Klebsiella sp. CW-D3T enhanced the remediation efficiency of target compounds, with the PHE and Cd²⁺ removal rates above 70.00% when the initial Cd²⁺ concentration was below 10 mg/L. As the concentration of Cd²⁺ increased, the secretion of extracellular polysaccharides in extracellular polymeric substances (EPS) was more than that of extracellular proteins, and the intensity of characteristic peaks of polysaccharides and protein functional groups on the surface of bacterial cells was enhanced. The initial activation of PHE in the sulfate reduction system tended to favor carboxylation to produce 2-phenanthroic acid under Cd²⁺ stress. When the initial Cd²⁺ concentrations were 10 mg/L and 50 mg/L, the content of 2-phenanthroic acid peaked at 15.56 μg/L and 10.23 μg/L on day 5, respectively, which decreased by 27.56% and 52.37% compared with that of the control group without the addition of Cd²⁺. Cd²⁺ stress significantly affected the 2-phenanthroic acid content within the cycle and at the end of the cycle. [Conclusion] The biodegradation efficiency of PHE by Klebsiella sp. CW-D3T was significantly improved when sulfate was used as an electron acceptor in the presence of Cd²⁺. The extracellular polysaccharides and proteins played a positive role in enhancing the microbial tolerance to Cd²⁺ stress by regulating the detoxification process.