一株氧化木糖无色杆菌对Cd的固定作用

Immobilization of Cd by a carbonate-biomineralization bacteria

【目的】研究一株氧化木糖无色杆菌LAX2对镉(Cd)的碳酸盐矿化作用及其对Cd污染稻田土壤的修复效果。【方法】将LAX2接种于含0~40mg/L Cd2+的牛肉膏蛋白胨液体培养基中,测定LAX2对Cd的耐受性。在LAX2发酵液中加入0.1mol/L CdCl2放置12h,利用X-射线衍射、红外光谱、扫描电镜和能谱对菌株LAX2矿化固结Cd的产物特征进行分析,并通过水稻盆栽试验验证菌株LAX2对Cd污染土壤的修复效果。【结果】菌株LAX2对Cd2+的耐受能力较强,当溶液中Cd2+质量浓度达35 mg/L时,其生长不受明显影响;但当Cd2+质量浓度为40mg/L时,LAX2生长受到明显抑制。矿化产物特征分析结果表明,菌株LAX2可通过碳酸盐矿化作用将Cd矿化为呈小颗粒团聚体的CdCO3晶体。Cd污染稻田土壤经菌株LAX2发酵液、无菌发酵液和菌体细胞修复后,水稻根部Cd含量分别下降了35.3%,19.4%和12.5%,茎叶Cd含量分别降低了26.7%,15.6%和8.4%,水稻籽粒中Cd含量分别降低了28.7%,16.4%和7.5%,土壤有效态Cd含量分别下降了56.9%,34.5%和21.0%。【结论】菌株LAX2可通过碳酸盐矿化作用固结土壤中的有效态Cd,从而减少水稻对Cd的吸收。

【Objective】This research aimed to investigate the carbonate mineralization of cadmium(Cd)and bioremediation of Cd-polluted paddy soil by strain Achromobacter xylosoxidans LAX2.【Method】LAX2 was inoculated in beef extract peptone liquid medium containing 0-40 mg/L Cd 2+,and the tolerance of CX to LAX2 was determined.CdCl 2 at concentration of 0.1 mol/L was added to LAX2 fermentation broth for 12 h and the bio-mineralization products were characterized by X-ray diffraction,infrared spectroscopy,scanning electron microscopy and energy spectrum analysis.The remediation of Cd-polluted paddy soil by strain LAX2 was studied using rice pot experiment.【Result】Strain LAX2 had stronger tolerance against Cd 2+and its growth was not affected when Cd 2+concentration was 35 mg/L,while the growth was significantly inhibited when Cd 2+concentration was 40 mg/L.Strain LAX2 could form small particle agglomerated CdCO 3 crystals by carbonate mineralization.Cd contaminated rice soil were remediated by the strain LAX2 fermentation broth,sterile fermentation broth and bacterial cells with Cd concentrations in rice roots decreased by 35.3%,19.4%and 12.5%,respectively.The contents of Cd in stem and leaf decreased by 26.7%,15.6%and 8.4%,the contents in rice grains decreased by 28.7%,16.4%and 7.5%,and soil available Cd contents decreased by 56.9%,34.5%and 21.0%,respectively.【Conclusion】Strain LAX2 could immobilize available Cd through carbonate mineralization and reduced Cd uptake by rice.