一株李氏禾内生细菌去除Cr(VI)的特性

Characteristics of Cr( VI) removal from Leersia hexandra by an endophytic bacteria isolated

李氏禾(Leersia hexandra)是中国境内发现的第一种铬超积累植物,该文对李氏禾内生菌及其除铬性能进行了研究。采用添加Cr(Ⅵ)的牛肉膏蛋白胨固体平板培养方法,从李氏禾根部分离筛选获得一株具有较强Cr(Ⅵ)抗性的内生细菌G04,分子生物学鉴定结果表明该菌株属于阴沟肠杆菌(Enterobacter cloacae)。采用摇瓶培养方法,以Cr(Ⅵ)去除率、总Cr(铬)的去除率以及菌体生物量为指标,考察了pH、温度、底物浓度、装液量、接种量、摇床转速以及反应时间等因素对Cr(Ⅵ)去除率、总铬去除率和菌株生长的影响。结果表明:在牛肉膏蛋白胨液体培养基中,菌株 E. cloacae G04去除Cr(Ⅵ)的较优反应条件为初始pH5.0、温度37 ℃、Cr(Ⅵ)浓度为100 mg·L^-1 、装液量80 mL(250 mL三角瓶)、接种量15%、摇床转速为120 r·min^-1 、反应时间48 h。在此条件下,菌株 E. cloacae G04对Cr(Ⅵ)和总铬的去除率分别为84%和8%。根据Cr(Ⅵ)去除率和总铬去除率的结果推测该菌株去除Cr(Ⅵ)的机制可能是以还原为主、吸附为辅。这表明李氏禾内生细菌 E. cloacae G04菌株具有较好的应用潜力,既有可能直接用于土壤、水环境铬污染的修复,也有可能作为促植物修复铬污染的后备菌株,另外可为深入研究李氏禾的铬积累作用机制提供参考。

Leersia hexandra is a chromium hyper-accumulative plant which was firstly found in China. The endophytic bacteria of L. hexandra and their removal capacity for Cr(Ⅵ) were studied. A Cr(Ⅵ)-resistant endophytic bacterium G04 was isolated from the roots of L. hexandra by solid plate culture method using the media of beef extract peptone containing Cr(Ⅵ). Biological identification results showed the strain belonged to Enterobacter cloacae . Effects of culture conditions, such as initial pH, temperature, Cr(Ⅵ) concentration, liquid volume, inoculation amount, shaking speed and culture time, on the removal rate of Cr(Ⅵ), removal rate of total Cr and the growth of the strain were studied in detail by shaking flask culture. The results showed that the optimal conditions for the removal of Cr(Ⅵ) by E. cloacae G04 were initial pH of 5.0, culture temperature of 37 ℃, substrate concentration of 100 mg·L^-1 , liquid volume of 80 mL in 250 mL conical flask, inoculum size of 15%, shaking speed of 100 r·min^-1 and culture time of 48 h. Under these conditions, the removal rate of Cr(Ⅵ) and total chromium were about 84% and 8%, respectively. The results of this study indicate that the endophytic bacteria Enterobacter cloacae G04 has better application potential for removing chromium. It may be used directly for remediation of soil and water environment contaminated of chromium, and also may be used as alternative strain for promoting plant remediation of chromium pollution. Furthermore, the result has an important refe- rence value for illuminating the mechanism of chromium hyper-accumulation of L. hexandra .