Pb2+对城市污水处理厂污泥中苏云金芽孢杆菌发酵的影响

以城市污水处理厂污泥为培养基,研究了添加Pb2+对Bt(Bacillus thuringiensis,苏云金芽孢杆菌)生长和晶体蛋白合成的影响,同时分析了Bt发酵过程中有效态Pb含量(以ρ计)的变化,并采用FTIR(傅立叶红外光谱)和XPS(X射线光电子能谱),初步探讨了Pb2+在Bt表面的作用机制.结果表明:污泥培养基在支持Bt生长代谢和降低重金属有效态含量方面均优于商用培养基,当初始ρ(Pb2+)高达400 mg/L时,与未添加Pb2+相比,污泥培养基中Bt活菌数与晶体蛋白产量约分别下降48%和54%,而商用培养基中约分别下降82%和75%,证实了污泥作为Bt发酵培养基的可行性;Bt对Pb2+有较好的耐受性,当ρ(有效态Pb)在80 mg/L以下时,Bt生长代谢不会受到显著影响.光谱学分析表明,Bt对Pb2+有少量吸附,从而降低Bt发酵过程中Pb的生物有效性,吸附位点主要为羟基,部分C O和S O也参与了吸附反应.

Effect of Lead Ions on Bacillus thuringiensisFermentation with Sewage Sludge as Medium

The effects of lead ions on the growth curves and crystal proteins synthesis of Bacillus thuringiensis(Bt) were investigated in sewage sludge.The variations of available lead were analyzed during Bt fermentation,and the adsorption mechanism of lead ions on Bt cells was also discussed using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy.The results show that the sewage sludge was superior to commercial medium in supporting Bt growth metabolism and reducing the available heavy metals.With the initial concentration of Pb2+ up to 400 mg/L,the number of viable cells and concentration of crystal protein decreased 48% and 54% respectively in sewage sludge,while the decreasing rates were 82% and 75% respectively in the commercial medium.These results confirm the feasibility of the sludge as a Bt fermentation medium.The results also indicated that Bt could resist efficiently with available lead concentration as high as 80 mg/L.Spectroscopy analysis indicated that Bt cells could reduce the bioavailability of lead by adsorption of the lead ions on their surfaces.The main adsorption sites were hydroxyl groups,and parts of carbonyl and sulfhydryl groups.