Biomining with bacteriophage: Selectivity of displayed peptides for naturally occurring sphalerite and chalcopyrite

Abstract

During mineral processing, concentrates of sulfide minerals of economic interest are formed by froth flotation of fine ore particles. The method works well but recovery and selectivity can be poor for ores with complex mineralogy. There is considerable interest in methods that improve the selectivity of this process while avoiding the high costs of using flotation chemicals. Here we show the first application of phage biotechnology to the processing of economically important minerals in ore slurries. A random heptapeptide library was screened for peptide sequences that bind selectively to the minerals sphalerite (ZnS) and chalcopyrite (CuFeS2). After several rounds of enrichment, cloned phage containing the surface peptide loops KPLLMGS and QPKGPKQ bound specifically to sphalerite. Phage containing the peptide loop TPTTYKV bound to both sphalerite and chalcopyrite. By using an enzyme-linked immunosorbant assay (ELISA), the phage was characterized as strong binders compared to wild-type phage. Specificity of binding was confirmed by immunochemical visualization of phage bound to mineral particles but not to silica (a waste mineral) or pyrite. The current study focused primarily on the isolation of ZnS-specific phage that could be utilized in the separation of sphalerite from silica. At mining sites where sphalerite and chalcopyrite are not found together in natural ores, the separation of sphalerite from silica would be an appropriate enrichment step. At mining sites where sphalerite and chalcopyrite do occur together, more specific phage would be required. This bacteriophage has the potential to be used in a more selective method of mineral separation and to be the basis for advanced methods of mineral processing.

Maximizing filamentous phage yield during computer-controlled fermentation

“…Other metal-binding phages are being considered for use as biofilms to decrease corrosion of metals [17]. In a novel application, we recently reported the use of filamentous phage in the recognition of naturallyoccurring minerals for potential use in a biomining setting [21].…”

“…This knowledge is being applied to the improvement of medical implants [12]. The list of metals to which phage-displayed peptides bind continues to grow [12][13][14][15][16][17][18][19][20][21]. Some of these semiconductor binding phages are being utilized in novel nanotechnology applications; for example, phages are being engineered to assist in the synthesis of nanowires [14,15].…”

Effects of bacteriophage on the surface properties of chalcopyrite (CuFeS2), and phage‐induced flocculation of chalcopyrite, glacial till, and oil sands tailings

“…The phage clone used in this study displays the sequence DSQKTNPS (VP12) and was shown to be highly selective for CuFeS 2 (Dunbar et al, 2008). Bacteriophage were produced and purified as described by Curtis et al (2009). Briefly, a single infected bacterial colony is grown up in NZY, the bacteria removed by centrifugation, and the phage purified by two sequential PEG/NaCl precipitations.…”

“…Using the technique of phage display and biopanning, we recently isolated phage that bind specifically to CuFeS 2 and sphalerite (ZnS; Curtis et al, 2009;Dunbar et al, 2008) and showed that large numbers of mineralbinding phage could be prepared by using computercontrolled fermentation (Grieco et al, 2009). The exact nature of the mineral-peptide interaction is unknown at present but not surprisingly, the mineral-binding peptide sequences contain primarily polar amino acids, both charged and uncharged.…”

Application of filamentous phages in environment: A tectonic shift in the science and practice of ecorestoration

“…Filamentous phages may also make their bacterial hosts less virulent or lower our dependency on pesticides to control pathogens, thereby contributing to sustainable restoration (Ahmad et al, 2014;Askora, Kawasaki, Fujie, & Yamada, 2012). Modified filamentous phages may also produce specific peptides or proteins that are useful in monitoring targeted toxins, toxicants, and pesticides in the environment and in holding soil particles together to reduce soil erosion (Curtis, Dunbar, & Macgillivray, 2013;Curtis, Hewitt, & Macgillivray, 2009;Curtis, Macgillivray, & Dunbar, 2011;Goldman et al, 2003;Goldman, Pazirandeh, Charles, Balighian, & Anderson, 2002). In fact, filamentous phages can bridge the gap between the efficacy of microbial activity in vitro and in the field.…”