Bioleaching Of Arsenic-rich Gold Ores With Bacterial Mixture Before And After Mutation And Study Of Community Shift

With the development of economic, high-grade gold ores are almost processed, low-grade gold ores become the main gold resources in the future. Thus, it is increasingly necessary to process ores of lower grade to meet demand, especially on arsenic-rich gold ores. Therefore, the effective recovery of gold from arsenic-rich gold ores become the hot spot and nodus in researches over the world. In this paper, original bacterial mixture were enriched in acid mine drainage of Dexing copper mine, Jiangxi Province, China, which was adopted to the study on bioleaching of arsenic-rich gold ores. Firstly, the optimize bioleaching conditions of arsenic-rich gold ores with bacterial mixture were obtained through orthogonal design. Secondly, RFLP and DGGE-PCR were used to study community shift of the bacterial mixture during the arsenic-rich gold ores bioleaching. Thirdly, excellent bacterial mutant was obtained through physical mutagenesis, which was used to the arsenic-rich gold ores bioleaching. Finally, a new strain Leptospirillum ferriphilum named YXW was isolated through serial dilution from bacterial mixture. The experimental results are as follows:In this paper, biodiversity of bacterial mixture was analyzed by RFLP. The results showed that the optimum pH and temperature for bacterial growth were2.0and40℃, and the bacterium was moderate thermophilic bacterial mixture including Leptospirillum spp. and Sulfobacillus spp. two putative divisions. In addition, Leptospirillum spp. was dominant in the bacterial mixture, representing52.5%of the total strains in bacterial mixture.For the influence of temperature, pulp density, initial pH and inoculation on the bioleaching of arsenic-rich gold ores, orthogonal design was used to obtain optimize bioleaching conditions. Orthogonal design results showed that optimize bioleaching condition of Fe was5%pulp density. initial pH1.5and10%inoculation, and optimize bioleaching condition of As was10%pulp density, initial pH1.5and30%inoculation. Under optimize bioleaching condition, the leaching rate of Fe reached to96.59%and As reached to97.12%at20days.In this study, DGGE-PCR was used to study the changes of the bacterial community in the process of arsenic-rich gold ores bioleaching,and community composition of bacterial mixture was analyzed by RFLP after20days bioleaching. DGGE profiles showed that there was a clear phenomenon of community shift during the whole process of arsenic-rich gold ores bioleaching with bacterial mixture. Leptospirillum spp. were dominant at the early bioleaching stage, and Sulfobacillus spp. became the predominant strains at the later bioleaching stage.The results of RFLP analysis indicated that Sulfobacillus spp. were dominant after20days bioleaching, the percentage increased from47.5%to80%. In addition, the percentage of Leptospirillum spp. had a decline from52.5%to20%. These results of RFLP analysis were similar to that of DGGE-PCR.UV, ultrasonic and microwave were adopted to treat bacterial mixture for obtaining excellent bacterial mutant. The results showed bacterial mutant with group Dl (UV60s+ultrasonic10min) had the best ferrous oxidation rate, the density of cells and activity of total protein, which was selected for arsenic-rich gold ore bioleaching. For bacterial mutant, after15days bioleaching, the extraction rate of iron reached95.7%, increased by1.8%and shortened the leaching time (I day). In addition, the extraction rate of arsenic reached to92.62%after12days, which was increased by2.7%and shortened the leaching time (4days), compared with that of the original bacteria.In this paper, a new strain named YXW was isolated through serial dilution from bacterial mixture. Characterization of16S rDNA indicated that strain YXW belonged to Leptospirillum ferriphilum, the optimal condition for its growth is temperature40℃and pH1.5. During gold concentrate ores bioleaching, the bacterial mutant after mutation by microwave10s was the most effective, the extraction rate of arsenic and iron reached to99.7%and76%after bioleaching10days, which was19.6%and17.7%higher than the original strain,respectively.