荚膜红假单胞菌A12降低水培水稻幼苗对镉的积累

Rhodopseudomonas capsulatum A12 Reduced Cadmium Accumulation in Hydroponic Rice Seedlings

中国水稻田中重金属镉污染严重,目前尚无经济有效的治理方法。从镉污染土壤中分离出一株荚膜红假单胞菌A12,探究其对Cd^(2+)的吸附性能及吸附机制。通过设置4个自变量:Cd^(2+)初始浓度、pH值、生物吸附剂用量和时间,研究该菌对Cd^(2+)的生物吸附。将A12施加在水培的水稻幼苗上,观察其对水稻幼苗生长和镉积累的影响。结果表明:A12在200 mg/L高浓度的Cd^(2+)培养基中仍保持活性;当Cd^(2+)初始浓度为200 mg/L、溶液pH值为7.0、投菌量为0.5 mg/L、吸附时间为120 min时,A12对Cd^(2+)的吸附量最大。通过动力学模拟换算发现,Cd^(2+)的生物吸附遵循准二级动力学模型,推测化学反应是吸附的限速步骤;利用X射线光电子能谱(XPS)研究发现,A12表面的烃基、酰胺基团和质子化氨基参与了Cd^(2+)的吸附过程;同时,A12还可以促进水稻幼苗的生长,减少水稻幼苗对Cd^(2+)的积累。上述结果表明荚膜红假单胞菌作为生物吸附剂可吸附Cd^(2+)并有效降低水稻幼苗对Cd^(2+)的积累。

The heavy metal pollution in paddy?elds is serious,and there is no economic and effective treatment method.A strain of Rhodopseudomonas capsulatus A12 was isolated from cadmium-contaminated soil to explore its adsorption capacity and mechanism of Cd^(2+).Four independent variables (initial concentration of Cd^(2+),pH,dosage and time of biosorbent) were set to study the biosorption of Cd^(2+)by the bacteria.The effects of A12 on the growth and cadmium accumulation of rice seedlings were observed by applying A12 to hydroponic rice seedlings.The results showed that A12 remained active in 200 mg/L Cd^(2+)medium.When the initial concentration of Cd^(2+)was 200 mg/L,the pH value of solution was 7.0,the dosage of bacteria was 0.5 mg/L,and the adsorption time was 120 min,the adsorption capacity of A12 to Cd^(2+)was the maximum.Through the conversion of kinetic simulation,it was found that the bioadsorption of Cd^(2+)followed the quasi-second-order kinetic model,and it was speculated that the chemical reaction was the ratelimiting step of adsorption.X-ray photoelectron spectroscopy (XPS) showed that the hydrocarbon group,amide group and protonated amino group on the surface of A12 were involved in the adsorption process of Cd^(2+).At the same time,A12could promote the growth of rice seedlings and reduce the accumulation of Cd^(2+)in rice seedlings.These results indicated that R.capsulatum could adsorb Cd^(2+)as a biosorbent and effectively reduce the accumulation of Cd^(2+)in rice seedlings.