Cr(VI)还原菌Microbacterium sp.BD6的分离鉴定及还原特性

Isolation, identification and characterization of Cr(VI) reducing bacterium Microbacterium sp. BD6

摘要:

[目的] 从电镀厂下水道的淤泥中分离筛选Cr（VI）高效还原菌，并对其生长和还原特性进行研究，以期为Cr（VI）污染的生物修复提供优质的菌种资源和应用参考。[方法] 采用富集培养法从淤泥中分离、筛选出Cr（VI）还原菌，通过生理生化及16S rRNA基因序列分析进行初步鉴定。采用单因素实验确定菌株的最佳培养条件和抵抗胁迫环境的能力，利用外加电子供体改善菌株的Cr（VI）还原能力，筛选出最佳电子供体研究对菌株还原的影响。[结果] 经分离筛选得到1株Cr（VI）耐受还原菌，初步鉴定为微杆菌属（Microbacterium sp.），命名为BD6。菌株BD6适宜在中温、偏碱性的环境条件下生长，能耐受50.0 g/L NaCl的高盐环境。Mn²⁺对菌种的生长表现出较高的抑制，Ni²⁺、Zn²⁺、Cd²⁺的抑制作用较小，Cu²⁺产生了一定的促进作用。Cr（VI）对BD6的最低抑菌浓度为1700 mg/L。添加甘油、果糖、乳糖、葡萄糖、丙酮酸钠作为电子供体促进了菌株对Cr（VI）的还原。选择甘油作为菌株还原Cr（VI）的最佳电子供体，无电子供体添加时菌株96 h内对100 mg/L Cr（VI）的还原率仅为69.63%，添加2 g/L的甘油菌株在36 h内的还原率达到了100%。通过加大甘油的添加量可以促进菌株对初始浓度较高Cr（VI）的还原，但要受到Cr（VI）的毒性限制。菌株的最适还原条件和最适生长条件吻合，在50.0 g/L NaCl的高盐条件和50 mg/L Cd²⁺的毒性环境中，添加2 g/L的甘油，菌株对100 mg/L Cr（VI）的还原率分别为72 h 96.79%、54 h 99.86%。[结论] 分离筛选得到的Microbacterium sp.BD6是一株潜在的可用于Cr（VI）污染生物还原修复的候选菌株。

Abstract:

[Objective] In order to provide high-efficient strains for bioremediation of Cr(VI) pollution, growth and reduction characteristics of a strain of highly efficient Cr(VI) reducing bacteria separated from sewer sludge of electroplating plant were studied. [Methods] Cr(VI) reducing strains were isolated and screened from sludge by enrichment culture method. The primary identification was carried out by physiological and biochemical analysis and 16S rRNA gene sequence analysis. Single factor experiments were used to determine the optimal culture conditions and the resistance characteristics to stress environment. In addition, the best electronic donor was screened out by investigating the effect of electronic donor on reduction ability of strain. [Results] An efficient Cr(VI) reducing strain was isolated and preliminarily identified as Microbacterium sp., named as BD6. Strain BD6 is suitable to grow in medium temperature and alkaline environment. Meanwhile, it can tolerate high-salt environment with NaCl concentration up to 50.0 g/L. The test showed that growth of the strain is strongly inhibited by Mn²⁺, slightly inhibited by Ni²⁺, Zn²⁺ and Cd²⁺ and promoted by Cu²⁺. The minimum inhibitory concentration of Cr(VI) on BD6 was 1700 mg/L. The reduction of Cr(VI) by BD6 is significantly improved by electronic donors, including glycerol, fructose, lactose, glucose and sodium pyruvate. Glycerol is considered as the best electron donor for the reduction of Cr(VI) by BD6. The reduction rate of 100 mg/L Cr(VI) is only 69.63% in 96 h without adding electron donor, however, it could reach 100% in 36 h after adding 2 g/L glycerol. The reduction of the strain to higher initial concentration of Cr(VI) can be enhanced by adding the amount of glycerol, but restrained by the toxicity of Cr(VI). Reduction test shows that the optimum reduction conditions and growth conditions of the strain are consistent. In the high-salt environment with NaCl concentration of 50.0 g/L and toxic environment with Cd²⁺ concentration of 50 mg/L, the reduction rate of the strain to 100 mg/L Cr(VI) are 96.79% within 72 h and 99.86% within 54 h respectively with presence of 2 g/L glycerol. [Conclusion] Microbacterium sp. BD6 is a potential candidate strain for bioremediation of Cr(VI) contamination.