耐镉甲基营养芽胞杆菌吸附条件的优化及其抗逆性

Optimization of cadmium adsorption conditions and anti-stress characteristics of a cadmium-tolerant Bacillus methylotrophicus strain

摘要:

[目的]对所筛选的1株耐镉甲基营养芽胞杆菌NTGB29进行了环境抗逆性的研究，及影响菌株吸附镉离子效率的条件优化。[方法]以发酵液活菌数为指标，研究其对不同NaCl浓度、酸碱度、镉离子浓度的耐受情况；进一步通过单因素实验和响应面法优化影响菌株镉离子吸附效率的发酵条件；以有效镉离子含量为指标，验证菌株在镉污染土壤中的吸附效果。[结果]结果表明，菌株NTGB29对NaCl浓度、酸碱度、Cd²⁺浓度的最大耐受值分别为10%、pH 11.0、50 mg/L；菌株在发酵液初始Cd²⁺浓度10 mg/L、起始pH 6.4、培养温度37℃、NaCl浓度4.2%、装液量50 mL/250 mL、培养时间24 h时，对Cd²⁺的吸附率达到79.70%；菌株能有效降低镉污染土壤中的有效镉离子含量，吸附率为29.65%。[结论]菌株NTGB29在较高浓度Cd²⁺浓度、NaCl浓度及强碱环境条件下仍然能够生长，具有良好的环境抗逆性及Cd²⁺吸附能力，在镉污染土壤调理剂及微生物功能菌剂的研制方面能够提供有价值的菌种资源。

关键词:甲基营养芽胞杆菌;抗逆性;镉离子吸附率

Abstract:

[Objective] To assess the anti-stress characteristics and to optimize the conditions affecting its cadmium ions adsorption efficiency of a cadmium-tolerant Bacillus methylotrophicus strain NTGB29. [Methods] The anti-stress characteristics were studied by plate colony-counting method. In addition, we used single factor experiment and response surface methodology to optimize the fermentation conditions of cadmium ions adsorption of the strain. Moreover, the available cadmium ions contents were used to verify the cadmium ions adsorption ability of the strain in the cadmium contaminated soils. [Results] The maximum tolerance of NTGB29 to NaCl, pH and concentration of Cd²⁺ was 10%, 11.0 and 50 mg/L, respectively. The optimum cadmium adsorption conditions were as follows:initial pH 6.4, culture temperature 37℃, NaCl concentration 4.2%, liquid volume 50 mL in the 250 mL flask, and culture time 24 h. Under the conditions, the cadmium ions adsorption percentage reached to 79.70%. In addition, the available cadmium ions of the cadmium contaminated soils was decreased significantly by adding strain NTGB29, and the adsorption percentage was 29.65%. [Conclusion] Strain NTGB29 has good environmental resistance and Cd²⁺ adsorption capacity, and it could be a kind of valuable strain source to develop the heavy metal contaminated soil conditioners and microbial functional agents.

Key words:Bacillus methylotrophicus;anti-stress characteristics;cadmium ions adsorption percentage