一株土壤产电菌Clostridium sporogenes的分离及其产电性能

Characterization of a novel electrogenic Clostridium sporogenes isolated from forest soil

摘要:

[目的] 从土壤中分离获得产电菌纯菌株SE6,鉴定其种类并分析其产电性能。[方法] 通过厌氧培养分离得到纯菌株,根据其形态、生理生化性质及16S rRNA基因测序分析确定其种属。以该菌株作为产电菌接种源,液体LB培养基和铁氰化钾溶液分别作为阳极液和阴极液,构建双室微生物燃料电池(Microbial fuel cells, MFCs),研究其产电能力;根据交流阻抗图谱,分析MFCs的内阻。应用循环伏安测试确定该菌株的胞外电子传递方式。并利用扫描电镜对阳极表面产电菌形态进行观察。[结果] 菌株SE6的16S rRNA基因序列与Clostridium sporogenes有100%同源性,结合其形态特征和生理生化特性,确定其属于梭菌属(Clostridium)。SE6接种到MFCs中可以获得44.42 mW/m²的最大功率密度。MFCs的阳极内阻、阴极内阻和欧姆内阻分别为(1488±193) Ω/cm²、(0.92±0.01) Ω/cm²和(20.69±1.76) Ω/cm²。其循环伏安图谱显示体系中存在电化学活性物质且峰值电流随扫速升高线性增大。扫描电镜观察到阳极表面聚集附着着长度约1 μm的杆菌。[结论] 本研究成功从土壤中分离出具有一定产电能力的菌株C. sporogenes SE6,可直接将电子传递至阳极,其产电过程阻抗较大。

Abstract:

[Objective] To identify and characterize an electrogenic bacterium SE6 isolated form forest soil. [Methods] Pure culture of the strain was obtained by anaerobic incubation. It was identified based on morphology, physiology and biochemistry, and 16S rRNA gene sequencing analysis. The strain was inoculated in a dual chamber microbial fuel cell with LB medium as anolyte and potassium ferricyanide as catholyte, to characterize its electrogenic ability. Electrochemical impedance spectroscopy was conducted to analyze internal resistances of the MFCs. Extracellular electron transfer mechanism of the strain was explored by cyclic voltammetry. Biofilm on the anode surface was observed using scanning electron microscope. [Results] The 16S rRNA gene sequence of strain SE6 was 100% phylogenetically related to Clostridium sporogenes. Their morphological, physiological and biochemical characteristics were identical. The maximum power density of the MFCs inoculated with SE6 was 44.42 mW/m². The anodic resistance, cathodic resistance and ohmic resistance were (1488±193) Ω/cm², (0.92±0.01) Ω/cm² and (20.69±1.76) Ω/cm², respectively. Cyclic voltammograms indicated the existence of an electrochemically active substance, of which the peak currents were linearly correlated with the scanning rates. The 1 μm-rodshaped bacteria densely attaching to the anode surface were observed in scanning electron micrographs. [Conclusion] A novel electrogenic strain of C. sporogenes was isolated from forest soil, which transfers electrons extracellularly to electrode with high resistance.