High‐rate ferric sulfate generation by a Leptospirillum ferriphilum‐dominated biofilm and the role of jarosite in biomass retainment in a fluidized‐bed reactor

Abstract

The aims of this work were to develop a high-rate fluidized-bed bioprocess for ferric sulfate production, to characterize biomass retention, and to determine the phylogeny of the enrichment culture. After 7 months of continuous enrichment and air aeration at 37 degrees C, the iron oxidation rate of 8.2 g Fe(2+) L(-1)h(-1) (4.5.10(-12) g Fe(2+) cell(-1) h(-1)) was obtained at a hydraulic retention time (HRT) of 0.6 h. However, oxygen supply became the rate-limiting factor. With gas mixture (99.5% O(2)/0.5% CO(2) (vol/vol)) aeration and HRT of 0.2 h, the iron oxidation rate was 26.4 g Fe(2+) L(-1)h(-1) (1.0.10(-11) g Fe(2+) cell(-1) h(-1)). Leptospirillum sp. was predominant in the mesophilic fluidized-bed reactor (FBR) enrichment culture as determined by fluorescent in situ hybridization, while Acidithiobacillus ferrooxidans was not detected. Denaturing gradient gel electrophoresis (DGGE) of the amplified partial 16S rDNA showed only three bands, indicating a simple microbial community. DGGE fragment excision and sequencing showed that the populations were related to L. ferriphilum (100% similarity in sequence) and possibly to the genus Ferroplasma (96% similarity to F. acidiphilum). Jarosite precipitates accumulated on the top of the activated carbon biomass carrier material, increasing the rate of iron oxidation. The activated carbon carrier material, jarosite precipitates, and reactor liquid contained 59% (or 3.71.10(9) cells g(-1)), 31% (or 3.12.10(10) cells g(-1)) and 10% (or 1.24.10(8) cells mL(-1)) of the total FBR microbes, respectively, demonstrating that the jarosite precipitates played an important role in the FBR biomass retention.

Characterization of a thermophilic sulfur oxidizing enrichment culture dominated by a Sulfolobus sp. obtained from an underground hot spring for use in extreme bioleaching conditions

“…In the field conditions, granular sulfur would be easier to manage, and therefore, the bioavailability in comparison to required oxidation rate should also be addressed at heap leaching conditions. The copper dissolution rate from chalcopyrite by the VS2 culture was dependent upon the solids concentration and adjustments of pH of the leaching solution, which has also been observed in other bioleaching experiments [21]. Copper dissolution rate and the overall yield observed with VS2 compares favorably with most of the other reported chalcopyrite leaching experiments in shake flask conditions at 50°C (Table 3).…”

“…Cultures where growth was detected were subcultured using 10% vol/vol transfers. Scanning electron microscopy was performed as reported by Kinnunen and Puhakka [21].…”

“…Consequently, these micro-organisms are being sought from mining sites, acid mine drainage, and geothermally active areas, where these kinds of conditions exist [e.g., 3,18,21,33]. Thermophilic and acidophilic sulfur/iron oxidizers dominating at a temperature range of 40-60°C are the typically rod-shaped, Sulfobacillus species [for reviews, see e.g., 12,35], although other species, such as Leptospirillum thermoferrooxidans, Acidimicrobium ferrooxidans, Acidithiobacillus caldus, and Hydrogenobacter acidophilus, are also commonly present [12,16].…”

Characterization of iron- and sulphide mineral-oxidizing moderately thermophilic acidophilic bacteria from an Indonesian auto-heating copper mine waste heap and a deep South African gold mine

“…The microbial community was investigated by PCR-DGGE followed by partial sequencing of 16S rRNA genes. Samples were filtered and washed [17] before nucleic acid extraction [16]. Crude DNA samples were used as templates for PCR.…”

“…PCR mixtures contained 5 ll 10x PCR buffer IV (200 mM (NH 4 ) 2 SO 4 , 750 mM Tris-HCl, 0.1% (v/v) Tween, pH 8.8), 1.75 mM MgCl 2 , 0.5 lM each primer, 100 lM each deoxynucleoside triphosphate, 1.25 U Red Hot DNA polymerase (ABgene, Advanced Biotechnologies, Epsom, UK), 400 ng ll )1 bovine serum albumin [18], and sterile water to a final volume of 50 ll, to which 1 ll template was added. PCR, DGGE and 16S rRNA gene sequencing were performed as described by Kinnunen and Puhakka [17] except that the DGGE electrophoresis was run for 16 h. Sequence data were initially analysed using basic local alignment search tool (BLAST) and further phylogenetic analyses were conducted using MEGA version 2.1 software [20].…”