城市污泥中重金属镉对苏云金杆菌发酵的影响机制

为揭示苏云金杆菌（Bacillus thuringiensis,简称Bt）富集重金属的可行性,考察重金属对Bt发酵的影响,以生物毒性较大的重金属镉（Cd）为研究对象,以城市污泥为培养基,研究了添加Cd（II）对Bt生长和晶体蛋白合成的影响,分析了Bt发酵过程中Cd有效态质量浓度的变化,利用傅立叶红外光谱（FTIR）和X线光电子能谱（XPS）初步探讨了Cd（II）在Bt表面吸附的作用机制。结果表明：培养基中外加Cd（II）对Bt生长的影响主要取决于Cd有效态质量浓度,污泥培养基在支持Bt生长和降低重金属有效态质量浓度上均明显优于常规培养基;Bt对Cd（II）有较好的耐受性,当Cd有效态质量浓度在20 mg.L-1以下时,Bt能较好地完成生长代谢过程;光谱学分析表明Bt对Cd（II）有少量吸附,吸附位点主要为羟基,少量C=O基团也可与吸附反应,可有效降低重金属的生物有效性。

Effects of heavy metal cadmium on Bacillus thuringiensis fermentation in sewage sludge

In order to reveal the potential of heavy metals bioaccumulation by Bacillus thuringiensis（Bt） and investigate the effect of heavy metals on Bt fermentation,cadmium（Cd） was chosen as research object in this paper for its high biological toxicity to human beings.The effect of cadmium ions on the growth curves variation and the crystal proteins synthesis of Bt were investigated with sewage sludge as medium.The variations of available cadmium were measured during Bt fermentation.The adsorption mechanism of cadmium ions on Bt cells was also discussed by means of Fourier transform infrared spectroscopy（FTIR） and X-ray photoelectron spectroscopy（XPS）.The results show that the effect of heavy metals on Bt growth depends on the available concentration of heavy metals,and sewage sludge is superior to commercial medium on supporting Bt growth metabolism and reducing the available heavy metals.Bt can resist efficiently with available cadmium concentration as high as 20 mg.L-1 Spectroscopy analysis indicates that Bt cells can reduce the bioavailability of cadmium by adsorbing the cadmium ions on their surfaces.The main adsorption sites are hydroxyl groups,and some carbonyl groups can also participate in the adsorption reaction.