Dear Colleagues,

Biometallurgy is a technology that extracts valuable metals from ores through the use of microorganisms. In this process, ores are decomposed under the actions of microorganisms, so that the valuable metals in the minerals are dissolved into or exposed onto solution, and further extracted using various physical and chemical methods, e.g., liquid-phase extraction, electrodeposition, adsorption. This technology has been successfully applied in metal extraction in a dozen of metals, e.g., Cu, Au, U, Zn, Ag, Ni, Co, Sn, Sb, and become one of the most important industrial methods of processing low-grade complex refractory ores. The environments of the minerals bioleaching are usually extremely acid and full of various toxic metal ions in very high concentrations; thus, the microorganisms that survive in these environments are considered a miracle of life and possess many peculiar abilities and properties. The microorganisms and these genes and proteins that they harbor are also precious resources for various applications’ developments, e.g., cell biosensors, Taq DNA polymerase enzyme. Therefore, studies in this field are of both great interest and great application significance.

We invite you to contribute to this Special Issue dedicated to biometallurgy and all its relevant aspects, e.g., minerals bioleaching, microorganisms, community structure and function, genes and proteins, microbe–mineral interface, solution reactions, metals extraction, mechanism and techniques, are in consideration.

Dr. Yuandong Liu
Prof. Dr. Ruiyong Zhang
Guest Editors

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• minerals bioleaching
• microbe–mineral interface
• solution reactions
• microorganisms
• community structure and function
• genes and proteins
• multiple bio-omics
• bioleaching mechanism
• biometallurgy techniques
• new applications development

Title: Isolation, identification and whole genome sequencing of a high active bioleaching microorganism of Acidithiobacillus ferriphilus
Authors: Yuandong Liu
Affiliation: Central South University, Changsha, China

Title: Bioleaching of argentite and its interfacial electrochemical behavior
Authors: Yuandong Liu
Affiliation: Central South University

Title: Expression, purification, characterization and direct electrochemistry of HiPIP from Acidithiobacillus ferrivorans SS3
Authors: Yuandong Liu
Affiliation: Central South University

Title: Pan-genomic analysis of Sulfobacillus thermosulfidooxidans reveals bioleaching mechanism of sulfide minerals
Authors: Yuandong Liu
Affiliation: Central South University

Title: Integrative chemical and omics analyses reveal bioleaching mechanism of chalcopyrite by Acidithiobacillus ferriphilus
Authors: Yuandong Liu
Affiliation: Central South University

Title: Bioleaching of lepidolite by an enriched acidophilic microorganism
Authors: LI Jingna, LIU Hongchang*, WANG Mengyuan, HUANG Shiyun
Affiliation: School of Minerals Processing and Bioengineering, Central South University, Changsha 410083, China; * [email protected]
Abstract: Bioleaching is a promising technology for minerals processing and separation, with low-cost and eco-friendly. In this paper, the bioleaching process, morphology, and composition changes during bioleaching of lepidolite was studied based on Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and 16S RNA high-throughput sequence analysis. The results showed that the leaching efficiency of lepidolite was 26.93% at 14 days of bioleaching, compared with the sterile control group (3.45%), and there was significant difference (p<0.05), indicating that the leaching effect was significantly promoted. The results had important reference value for the optimization of the bioleaching process of lepidolite

Title: Mesophilic bioleaching of chalcopyrite concentrate mixed with limestone
Authors: Yuandong Liu*, Guanzhou Qiu, Jiaju ji, Xueduan Liu, Xinxing Liu
Affiliation: Key Laboratory of Biometallurgy, Ministry of Education,School of Minerals Processing and Bioengineering, Central South University, Changsha, Hunan 410083, P. R. China
Abstract: When mixed with proper limestone, mesophilic bioleaching of chalcopyrite concentrate by an acidophilic consortium showed good performance. The assay results showed that the concentration of CO2 and the amount of microorganisms in the sample mixed with limestone was obviously more than those in the sample unmixed with limestone. So it suggested that limestone can provide abundant carbon source to the microorganisms and then accelerate their growth to perform more bioleaching function. Furthermore, the bacterial community structure was analyzed by using Amplified Ribosomal DNA Restriction Analysis and real-time PCR showed four predominant bacteria, Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans, Acidithiobacillus thiooxidans and Acidiphilium acidophilum in the sample mixed with limestone. The whole microorganisms prefer to grow on the minerals surface, which were also with more amount than that in the solution. A. ferrooxidans could be always detected during bioleaching both on the minerals surface and in the solution. L. ferrooxidans was mainly on the minerals surface. A. thiooxidans was mainly in the solution. A. acidophilum appeared at later stage

Title: Hydrophobic adsorption enables direct electrochemistry of iron oxidase on 4,6-dimethyl-2-pyrimidinethiol modified gold electrode
Authors: Yuandong Liu*, Xiangdong Shangguan, Run Liu, Jiayu He, Wissal Belqadi, Kan Wang, and Yan Tong
Affiliation: Key Laboratory of Biohydrometallurgy of Ministry of Education, School of Minerals Processing and Bioengineering, Central South University, Changsha 410083, China
Abstract: Iron oxidase (Iro) plays a crucial role in ferrous biooxidation of Acidithiobacillus genus bacteria but its fundamental redox potential remains undetermined due to lack of successful electrochemistry method. Here, a recombinant Iro from A. ferrianus and its mutant proteins were constructed, overexpressed, and purified. These proteins were used to explore the direct electrochemistry methods of Iro and investigated the underlying mechanism. The successful electrochemistry of Iro on some pyrimidinethiols modified gold electrodes were found, the stronger the non-polarity of the groups on the pyridine ring of modifiers, the better the electrochemical effects, and the 4,6-Dimethyl-2-pyrimidinethiol (DMMP) achieved the best effect. The redox potential of Iro was determinated and its electrochemistry showed an interface electrochemical polarization dynamics control process. Electrochemical impedance spectroscopy analysis and scanning probe microscope observation revealed that protein adsorption on the surface of DMMP-modified gold was formed. Bioinformatics analysis and molecular simulation uncovered the interactional configuration of the protein with its large hydrophobic surface faced and closed to the surface of DMMP-modified gold. Structure-guided mutagenesis of the protein on electrochemistry confirmed that the hydrophobic surface residues are very crucial for the success of electrochemistry, their changes to hydrophility caused weak or loss of electrochemistry siganal. All the results suggest that hydrophobic adsorption enables direct electrochemistry of Iro on non-polar surface-modified gold electrode. Overall, our study contributes to uncovering the role of the protein in ferrous biooxidation, lays the foundation for its application in biosensor, and systematically exhibits a paradigm of direct protein electrochemistry caused by hydrophobic interaction

Title: Insights into the cyoA gene in the sulfur oxidation from Acidithiobacillus ferrooxidans
Authors: Jia-qi LIANG, Yuan-dong LIU*, Ning-ning AN, Jing-ying OUYANG, Wei-min ZENG , Run-lan YU, Jiao-kun LI, Xue-ling WU, Li SHEN,Wen-qing QIN, Guan-zhou QIU
Affiliation: Key Laboratory of Biometallurgy, Ministry of Education,School of Minerals Processing and Bioengineering, Central South University, Changsha, China;
Abstract: Acidithiobacillus ferrooxidans has different terminal oxidases (cytochrome aa3 complex, cytochrome bo3 complex and so on). Particularly, the role of the cytochrome bo3 complex, encoded by the gene cluster cyoABCD, in A. ferrooxidans is still under reveal. Here we report the differential gene transcription, bioinformatics analysis and molecular modeling of the subunit II of the cytochrome bo3 complex encoded by the cyoA gene from A. ferrooxidans (CyoA). The qRT-PCR results showed that the expressions of the cyoA gene were significantly upregulated in the conditions of pyrite culture for the cells attached on mineral surface, thiosulfate culture and, particularly, sulfur culture. Bioinformatics analysis indicated that the CyoA was affiliated to the heme-copper oxidase superfamily subunit II, contained a membrane lipid attachment site, a cupredoxin-like fold absent four copper binding residues and an aromatic rich motif. Molecular modeling results further exhibited that the CyoA protein had no cytochrome c binding site, nor two-Cu center akin to cytochrome c oxidase subunit II. So the CyoA in A. ferrooxidans functions as the subunit II of an ubiquinol terminal oxidase and plays a role in the sulfur or RISCs (reduced inorganic sulfur compounds, e.g. element sulfur, thiosulfate) oxidation in bioleaching

Title: OA strengthens the removal ability of a biosynthetic surface-modified schwertmannite/graphite composite for Cr(VI) reduction
Authors: Min Gan*, Chenzi Huang, Yao Xiong, Dandan Yang, Jianyu Zhu
Affiliation: Key Laboratory of Biohydrometallurgy of Ministry of Education, School of Minerals Processing and Bioengineering, Central South University, Changsha 410083, China
Abstract: Schwertmannite was selected to load on graphite to produce a pyrolysis composite material for efficient removal of Cr(VI). Characterization of the composite demonstrated that it possesses the properties of both graphite and Schwertmannite, with stable electron supply capacity and electrical conductivity, which can effectively catalyze the reduction of Cr(VI) to Cr(III). To enhance the removal effect, oxalic acid was selected to increase the dissolution rate of Fe in the material surface and promote the redox cycle of iron and chromium. The batch experiment results showed that when the roasting temperature was controlled at 700 ℃, [email protected] 700 ℃ could reduce 90.42% of Cr(VI) within 60 min after the addition of oxalic acid, which indicated that oxalic acid and the composite material could be used for the efficient removal of Cr(VI). In addition, the prepared composites were magnetic and could be easily recycled. In conclusion, considering the removal efficiency, recyclability, cost, and stability of the system, the joint removal of Cr(VI) by [email protected] 700 ℃ and oxalic acid provides an excellent demonstration of reducing Cr(VI) in aqueous