一株黑曲霉的分离鉴定及其对土壤重金属的生物浸出效果

Isolation and identification of Isolation and identi cation of Aspergillus niger Y9 and its role in bioleaching of metal contaminants from soils

某些真菌可产生小分子有机酸,既具有酸化环境介质的功能,又具有络合重金属能力,因此可有效浸出环境介质(如土壤、底泥等)中的重金属.本研究从土壤中分离得到一株产酸能力较高的真菌,经形态学及ITS rDNA基因序列分析鉴定为黑曲霉,命名为Aspergillus niger Y9.测定了其生长特性,并采用摇瓶培养法探究其同步、分步培养法去除污染土壤中重金属的效果.结果显示,该菌适宜生长pH范围较广(3.0-8.0),对Zn2+、Cd2+、Pb2+的80%抑制浓度分别为250、130、2 700 mg/L.培养20 d后pH降至2.1,柠檬酸、葡萄糖酸、草酸和苹果酸的产量分别为54.8、20.1、15.9、6.3mmol/L.分步培养法污染土壤中重金属的浸出率最高为Zn 75%,Cd 100%,Pb 43%,略优于同步培养法(Zn 64%,Cd86%,Pb 19%).上述结果表明,Aspergillus niger Y9具有较强的重金属耐受性,能有效浸出土壤中的Zn、Cd、Pb,为后期采用该菌处理重金属污染土壤提供了技术参考.

Fungus is reported to have the capability of producing organic acids that can serve as leaching agents for removing heavy metals from the environment. In this study, an acid-producing heterotrophic fungus named Y9 was isolated from soil and identified as Apergillus niger through morphological and molecular identification. Furthermore, its growth and acid production characteristics, as well as its application in leaching heavy metals from contaminated soil by the one-step and two-step bioleaching processes were investigated and evaluated in shake flask culture. The results showed that A. niger Y9 had not only a wide range of optimal pH value from 3.0 to 8.0, but also a strong tolerance to Zn2＋, Cd2＋ and Pb2＋ and the 80% inhibitory concentration was 250 mg/L, 130 mg/L, 2 700 mg/L, respectively. After incubating for 20 days, this fungus excreted 54.8 mmol/L citric acid, 20.1 mmol/L gluconic acid, 15.9 mmol/L oxalic acid and 6.3 mmol/L malic acid. As a result, pH value of the pure culture system declined to 2.1. Besides, in the bioleaching experiment, the two-step process exhibited a relatively higher leaching efficiency of heavy metals with a maximum solubilization of 75% Zn, 100% Cd and 43% Pb, as compared to the one-step bioleaching process with removal efficiencies of 64% Zn, 86% Cd, and 19% Pb. It implied that Aspergillus niger Y9 has a good resistance of heavy metals and could be used to remove heavy metals from contaminated soils.