Isolation and Molecular Characterization of Two Bacterial Strains with Higher Bioleaching Potentials, from Agbaja Mines (Kogi State, Nigeria)

Abstract

Bacterial strains with higher bioleaching capacity (BC) are relevant for the mining industry, being more eco-friendly methods, for instance more than cyanide based extraction.  Microbiological samples were collected from selected sites in Agbaja Mines, which after a growth enrichment step, cultures were screened for iron BC, including chemical quantification of iron species. Strains with the highest BC were morphologically, biochemically and molecularly characterized. Two bacterial strains with iron BC Leptospirillum sp. And Acidithiobacillus sp. (AGBAJA-1 and AGBAJA-2, respectively) were isolated from Agbaja Mines of Kogi State Nigeria.  Bioleaching studies carried out shows that prior to inoculation of the iron ore solution with the organisms, raw Agbaja iron ore had a concentration of 25.10 mg/g iron while Zinc, Copper and Lead were 1.3903 mg/g, 0.094 mg/g, and 0.2813 mg/g respectively from X-ray diffraction analysis. The degree of bioleaching as a function of the amount of iron leached into solution was higher (in four weeks bioleaching test) than the other metals. Molecular characterization by sequencing  the 16S ribosomal unit, amplification with universal primers, yielded high quality amplicons that were sequenced.  Their phylogenetic/Blast comparison showed more than 97% relationships with Acidithiobacillus ferroxidans ATCC 23270 and Leptospirillum ferrovirans DSM 15468, families of bacteria in the National Centre for Biotechnology Information (NCBI) data bank. These are moderately thermophilic acidophilic bacteria that may represent an opportunity for developing a greener iron extraction process.