Xuehui Xie

Microbial diversity in acid mineral bioleaching systems of dongxiang copper mine and Yinshan lead–zinc mine

To understand the composition and structure of microbial communities in acid mineral bioleaching systems, the molecular diversity of 16S rDNA genes was examined using a PCR-based cloning approach. A total of 31 Operational Taxonomic Units (OTUs) were obtained from the four samples taken from four different bioleaching sites in Yinshan lead–zinc mine and Dongxiang copper mine in Jiangxi Province, China. The percentages of overlapping OTUs between sites ranged from 22.2 to 50.0%. Phylogenetic analysis revealed that the bacteria present at the four bioleaching sites fell into six divisions, α-Proteobacteria (1.1%), β-Proteobacteria (2.3%), γ-Proteobacteria (30.8%), Firmicutes (15.4%), Actinobacteria (0.3%) and Nitrospira (50.1%). Organisms of genera Leptospirillum, Acidithiobacillus, and Sulfobacillus, which were in Nitrospira, γ-Proteobacteria, and Firmicutes divisions, respectively, were the most dominant. The results of principal component analysis based on the six phylogenetic divisions and biogeochemical data indicated that the microbial community structure of a site was directly related to the biogeochemical characteristic of that site. It follows therefore that sites with similar biogeochemical characteristics were comprised of similar microbial community structures. The results in our study also suggest that the elements copper and arsenic appear to be the key factors affecting the compositions and structures of microbial community in the four bioleaching sites.

Characteristics, Process Parameters, and Inner Components of Anaerobic Bioreactors

The anaerobic bioreactor applies the principles of biotechnology and microbiology, and nowadays it has been used widely in the wastewater treatment plants due to their high efficiency, low energy use, and green energy generation. Advantages and disadvantages of anaerobic process were shown, and three main characteristics of anaerobic bioreactor (AB), namely, inhomogeneous system, time instability, and space instability were also discussed in this work. For high efficiency of wastewater treatment, the process parameters of anaerobic digestion, such as temperature, pH, Hydraulic retention time (HRT), Organic Loading Rate (OLR), and sludge retention time (SRT) were introduced to take into account the optimum conditions for living, growth, and multiplication of bacteria. The inner components, which can improve SRT, and even enhance mass transfer, were also explained and have been divided into transverse inner components, longitudinal inner components, and biofilm-packing material. At last, the newly developed special inner components were discussed and found more efficient and productive.

Microbial Communities in Acid Mine Drainage and Their Interaction with Pyrite Surface

Microbes such as Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans have been investigated a lot, because of their important role in acid mine drainage (AMD) generation. In this article, the composition of microbial communities in two AMD samples was studied. A culture-independent 16S rDNA-based cloning approach, restriction fragment length polymorphism has been used. The interaction between microbes and natural pyrite specimen surface was researched by scanning electrode microscopy (SEM) and fluorescence in situ hybridization (FISH). The phylogenetic analysis revealed bacteria in these two samples fell into three major groups: Proteobacteria, Nitrospira, and Firmicutes. Archaea was also detected in these two samples. Thermoplasma and Ferroplasma lineages were abundant. From SEM and FISH, a number of A. ferrooxidans, a few cells of Archaea and Acidiphilium were detected adsorbed on the pyrite specimen surface. Leptospirillum sp. (hybridize with the probe LF655) has not been detected to be present on the pyrite specimen surface.

Microbial communities in acid water environments of two mines, China

To understand the compositions and structures of microbial communities in different acid-aqueous environments, a PCR-based cloning approach was used. A total of five samples were collected from two mines in China. Two samples, named as G1 and G2, were acid mine drainage (AMD) samples and from Yunfu sulfide mine in Guangdong province, China. The rest of the three samples named as D1, DY and D3, were from three sites undertaking bioleaching in Yinshan lead-zinc mine in Jiangxi province, China. Phylogenetic analysis revealed that bacteria in the five samples fell into six putative divisions, which were alpha-Proteobacteria, beta-Proteobacteria, gamma-Proteobacteria, Firmicutes, Actinobacteria and Nitrospira. Archaea was only detected in the three samples from Yinshan lead-zinc mine, which fell into two phylogenentic divisions, Thermoplsma and Ferroplasma. In addition, the results of principal component analysis (PCA) suggested that more similar the geochemical properties in samples were, more similar microbial community structures in samples were.

Experimental measurements of short-term adsorption of Acidithiobacillus ferrooxidans onto chalcopyrite

Abstract The influencing factors in adsorption such as adsorption time, pulp concentration, bacterial concentration, pH as well as ionic strength were investigated to explore the relationship among them and bacterial adsorption. The adsorption was a rapid process for bacterial adhesion to chalcopyrite. The extent of adsorption increased with increasing initial bacterial concentration and pulp concentration. The optimal pH for Acidithiobacillus ferrooxidans adsorption onto chalcopyrite surfaces was in the range of pH 1-3. The increase of ionic strength led to decrease in bacterial adsorption, which can be well explained by electric double layer theory. The adsorption behavior appeared to be controlled by both hydrophobic and electrostatic interactions at the interface of bacteria and mineral.

Compositions and Structures of Archaeal Communities in Acid Mineral Bioleaching Systems of Dongxiang Copper Mine and Yinshan Lead–Zinc Mine, China

Four samples were studied from four separated sites with heap leaching in the Yinshan Lead–Zinc Mine and the Dongxiang Copper Mine in Jiangxi province, China. The compositions and structures of archaeal communities in four sites were identified by a polymerase chain reaction-based cloning approach. A total of six operational taxonomic units (OTUs) was obtained from four samples. The highest percentage of overlapped OTUs was 88.9% between sites DX and D1. Phylogenetic analysis revealed that archaea in the four acid mineral bioleaching systems fell into two divisions: Thermoplasma and Ferroplasma. The proportions of Thermoplasma and Ferroplasma in all four sites were 20.6% and 79.4%, respectively. The proportions of clones clustered with Ferroplasma in four sites were 93.8% (D1), 30.5% (D3), 100% (DY), and 93.2% (DX), respectively. The proportions of clones clustered with Thermoplasma in the other three sites were 6.2% (D1), 69.5% (D3), and 6.8% (DX), respectively. The results of principal component analysis based on the percentages of six OTUs obtained from four sites and geochemical data from four sites suggested that the concentrations of elements such as lead, cobalt, and sulfur might be the reason causing the different archaeal structure in site D3 than those in the other three sites.

Performance and microbial community structures of hydrolysis acidification process treating azo and anthraquinone dyes in different stages

In this study, performance of hydrolysis acidification process treating simulated dyeing wastewater containing azo and anthraquinone dyes in different stages was investigated. The decolorization ratio, CODCr removal ratio, BOD5/CODCr value, and volatile fatty acids (VFAs) production were almost better in stage 1 than that in stage 2. Fourier transform infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC-MS) confirmed the biodegradation of Reactive Black 5 (RB5) and Remazol Brilliant Blue R (RBBR) in hydrolysis acidification process. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analyses revealed that significant difference of microbial community structures existed in stage 1 and 2. The dominant species in stage 1 was related to Bacteroidetes group, while the dominant species in stage 2 was related to Bacteroidetes and Firmicutes groups. From the results, it could be speculated that different dyes’ structures might have significant influence on the existence and function of different bacterial species, which might supply information for bacteria screening and acclimation in the treatment of actual dyeing wastewater.

Effects of mutation on a new strain Leptospirillum ferriphilum YXW and bioleaching of gold ore

Abstract Leptospirillum ferriphilum YXW was isolated through serial dilution from mixed microorganisms enriched in AMD from Dexing copper mine in Jiangxi Province, China. It was mutated by ultrasonic, UV and microwave to collect more efficient strain for bioleaching of gold ore. Physiological and biochemical characteristics indicate that strain YXW is a strict chemoautotrophic microorganism, and the optimal condition for its growth is temperature of 40 °C and pH 1.5. After mutation by ultrasonic, UV and microwave, the density of bacterial cells reached 9×109, 8.4×109 and 4.3×108 mL−1, increased by 291%, 265% and 87%, respectively, compared with the original culture. The bacterial total protein activity was improved by microwave and UV mutations, but was reduced by ultrasonic. Mutations had effects on bioleaching of gold ore in sequence of microwave > UV > ultrasonic. During gold ore bioleaching, the bacterial mutant after mutation by microwave had the best effect on the extraction rates of arsenic and iron, which were 19.6% and 17.7% higher than that of the original strain after bioleaching for 10 d, respectively. The results suggested that the effects of mutation on bioleaching of gold ore may not be mainly due to increase of bacterial cells density, but may be mainly attributed to the improvement of bacterial total protein activity.

Characteristics of estrogenic/antiestrogenic activities during the anoxic/aerobic biotreatment process of simulated textile dyeing wastewater

The presence of estrogenic/antiestrogenic chemicals in textile dyeing wastewater has been well demonstrated according to previous studies. However, the characteristics of estrogenic/antiestrogenic activities during conventional biological treatment have been poorly investigated. In this study, the yeast two-hybrid assay (YES) was used to evaluate the agonistic and antagonistic estrogen activities during the anoxic/aerobic treatment of textile dyeing wastewater. The results indicated that the estrogenic activity of the textile dyeing wastewater was negligible throughout the anoxic/aerobic treatment, but the antiestrogenic activity increased obviously after the aerobic treatment. By fractionating the dissolved organic matter (DOM) in wastewater into different fractions, it was found that hydrophobic acids (HOA) and hydrophobic neutrals (HON) were the key fractions involved in increasing antiestrogenic activity of the wastewater during anoxic/aerobic treatment. Furthermore, the fluorescence spectroscopy analysis on wastewater samples and their fractions of soluble organic compounds suggested that HOA and HON fractions contained more humic/fulvic acid in aerobic effluent than that in anoxic effluent, which could mask estrogenic activity in aerobic effluent.

Bioleaching of Arsenic-Rich Gold Concentrates by Bacterial Flora before and after Mutation

In order to improve the bioleaching efficiency of arsenic-rich gold concentrates, a mixed bacterial flora had been developed, and the mutation breeding method was adopted to conduct the research. The original mixed bacterial flora had been enrichedin acid mine drainage of Dexing copper mine, Jiangxi Province, China. It was induced by UV (ultraviolet), ultrasonic, and microwave, and their combination mutation. The most efficient bacterial flora after mutation was collected for further bioleaching of arsenic-rich gold concentrates. Results indicated that the bacterial flora after mutation by UV 60 s combined with ultrasonic 10 min had the best oxidation rate of ferrous, the biggest density of cells, and the most activity of total protein. During bioleaching of arsenic-rich gold concentrates, the density of the mutant bacterial cells reached to 1.13 × 108 cells/mL at 15 days, more than 10 times compared with that of the original culture. The extraction of iron reached to 95.7% after 15 days, increased by 9.9% compared with that of the original culture. The extraction of arsenic reached to 92.6% after 12 days, which was increased by 46.1%. These results suggested that optimum combined mutation could improve leaching ability of the bacterial flora more significantly.