Characterization and uranium bioleaching performance of mixed iron- and sulfur-oxidizers versus iron-oxidizers

Sulfur enhancement effects for uranium bioleaching in column reactors from a refractory uranium ore

“…However, it would be transferred into jarosite on the surface of ore particles if only using iron-oxidizers like L. ferriphilum , or using iron/sulfur-oxidizers like A. ferrooxidans without enough sulfur as growth substrate. When using the single microbial species or single energy substrate, it would lead to the passivation accumulation on the mineral surface, which acts as a barrier against the diffusion of ions and then inhibits the uranium dissolution (Li et al, 2017 ). Herein, mixed iron-oxidizing bacteria and sulfur-oxidizing bacteria assist metabolic activities cooperatively and decompose minerals more effectively when presented at an appropriate Fe/S ratio in bioleaching operations.…”

“…In this way, the leaching efficiency was improved. The contribution of A. thiooxidans to the leaching efficiency was especially obvious in the initial bioleaching phase (Brune and Bayer, 2012 ; Li et al, 2017 ). It is noteworthy that the iron-oxidizers ( L. ferriphilum and A. ferrooxidans ) and sulfur-oxidizer A. thiooxidans maintained a good balance (nearly 1:1) on the ore surface at the sulfur dosage of 1 g/kg ( Figure 6 ).…”

“…The leaching organisms were activated by inoculating in 100 mL culture medium to an initial density of ~5 × 10 5 cells/mL (determined by hemocytometry) in 250-mL Erlenmeyer flasks. The medium was the 0K basal salt medium [(NH 4 ) 2 SO 4 3 g/L, KCl 0.1 g/L, K 2 HPO 4 0.5 g/L, MgSO 4 ·7H 2 O 0.5 g/L, Ca (NO 3 ) 2 0.01 g/L, pH 2.2 adjusted with H 2 SO 4 , sterilized at 120 °C for 20 min] (Selkov et al, 2000 ; Li et al, 2017 ). 44.7 g/L FeSO 4 ·7H 2 O were added for A. ferrooxidans ATCC 23270 and L. ferriphilum YSK as energy source, while 10 g/L elemental sulfur for A. thiooxidans A01.…”

“…The procedure was repeated for five times to collect effectively the attached microorganisms. Both the genomic DNA of the attached microorganisms and planktonic cells was extracted using the TIANamp ® Bacteria DNA kit (Tiangen Biotech Co. Ltd., Beijing, China) (Li et al, 2017 ). The DNA samples were checked on 1% agarose gel, and DNA concentration and purity were determined with a NanoDrop 2000 UV-vis spectrophotometer (Thermo Scientific, Wilmington, USA).…”

“…Chemoautotrophic leaching bacteria can gain ATP by the oxidation of ferrous iron and/or reduced inorganic sulfur compounds (Vera et al, 2013 ; Ma et al, 2017 ). It was demonstrated that mixed iron-oxidizing bacteria and sulfur-oxidizing bacteria decompose minerals more effectively when presented as symbiotic consortia in bioleaching operations (Brune and Bayer, 2012 ; Li et al, 2017 ).…”