一株氧化木糖无色杆菌对Pb的生物矿化作用及其应用效果研究

Biomineralization of Pb by a strain of Achromobacter xylosoxidans and its practical application in bioremediation

为了筛选可用于Pb污染土壤生物修复的优良菌种,研究了一株氧化木糖无色杆菌LAX2利用含尿素培养基生长的发酵液对Pb的生物矿化作用,及其对土壤中Pb的固定效果,结果表明当培养基中Pb的浓度低于105 mg·L^(-1)时,菌株LAX2的生长不受明显影响,扫描电子显微镜、X射线衍射分析、傅里叶红外光谱分析和能谱分析结果表明,菌株LAX2在含有尿素的培养体系中生长产生的发酵液可通过生物矿化作用形成一种球形的Pb CO_3晶体,其最大直径可达2μm。生物矿化、菌体细胞吸附和化学沉淀对Pb^(2+)的去除率分别为86.3%、91.6%和67.4%,表明三者存在不同的作用机制。菌株LAX2发酵液添加到土壤中培养,2 d后有效态Pb的浓度开始迅速下降,第5 d开始变缓,但在30 d的培养周期内有效态Pb的浓度一直呈现下降的趋势,培养5、10、30 d后,土壤中有效态Pb的含量分别下降了56.1%、76.5%和86.8%。向Pb污染土壤中加入发酵液、无菌发酵液、菌体细胞后进行小白菜盆栽试验,与对照相比,小白菜的株高分别增加了49.4%、21.6%和9.6%;土壤中有效态Pb含量分别降低78.1%、64.2%和52.4%,小白菜中Pb的含量分别下降了56.5%、27.4%和14.5%。以上研究结果表明菌株LAX2可通过生物矿化作用形成晶体结构的Pb CO_3,进而固定土壤中的有效态Pb,降低Pb对植物的毒害及其在植物体内的积累,因此在Pb污染土壤的生物修复当中具有重要的应用价值。

The biomineralization of Pb by a fermentation broth of bacterial strain Achromobacter xylosoxidans LAX2 growing in a urea-containing medium, and the effect of Pb immobilization effect in soil, were studied. The results showed that the growth of LAX2 was not significantly affected when the concentration of Pb in the medium was less than 105 mg·L^-1. Scanning electron microscopy, X-ray diffraction analysis, Fourier transform infrared spectroscopy, and energy spectrum analysis showed that the fermentation broth produced by the LAX2 growing in a urea-containing culture system formed a spherical Pb CO_3 crystal, with a maximum diameter of 2 μm, by biomineralization. The Pb^2＋removal rates via biomineralization, bacterial cell adsorption, and chemical precipitation were 86.3%, 91.6%, and 67.4% respectively, indicating that there were different mechanisms in the three processes. Two days after incubation with the LAX2 fermentation broth, the amount of available Pb in the soil decreased rapidly; but after 5 d, the tendency slowed down. Overall, the amount of available Pb in the soil showed a declining trend during 30 d of incubation. The content of available Pb in the soil decreased 56.1%,76.5%, and 86.8% after 5, 10, and 30 d of incubation, respectively. Compared with the control groups, the addition of fermentation broth, sterile fermentation broth, and bacterial cells to Pb-contaminated soil increased the heights of Chinese cabbage plants by 49.4%, 21.6%, and 9.6%, respectively;the content of available Pb in the soil decreased by 78.1%, 64.2%, and 52.4%, respectively; and the content of Pb in the Chinese cabbage decreased by56.5%, 27.4%, and 14.5%, respectively. These results indicate that the strain LAX2 has important value in bioremediation of Pb-contaminated soil, due to its ability to form crystalline Pb CO_3 with via biomineralization, leading to Pb immobilization and a reduction of Pb toxicity to, and accumulation in plants.