Culturable microorganisms associated with Sishen iron ore and their potential roles in biobeneficiation

Abstract

With one of the largest iron ore deposits in the world, South Africa is recognised to be among the top ten biggest exporters of iron ore. Increasing demand and consumption of this mineral triggered search for processing technologies, which can be utilised to "purify" the low-grade iron ore minerals that contain high levels of unwanted potassium (K) and phosphorus (P). This study investigated a potential biological method that can be further developed for the full biobeneficiation of low-grade iron ore minerals. Twenty-three bacterial strains that belong to Proteobacteria, Firmicutes, Bacteroidetes and Actinobateria were isolated from the iron ore minerals and identified with sequence homology and phylogenetic methods. The abilities of these isolates to lower the pH of the growth medium and solubilisation of tricalcium phosphate were used to screen them as potential mineral solubilisers. Eight isolates were successfully screened with this method and utilised in shake flask experiments using iron ore minerals as sources of K and P. The shake flask experiments revealed that all eight isolates have potentials to produce organic acids that aided the solubilisation of the iron ore minerals. In addition, all eight isolates produced high concentrations of gluconic acid followed by relatively lower concentrations of acetic, citric and propanoic acid. Scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) analyses also indicated extracellular polymeric substances could play a role in mineral solubilisation.

Two-Phase Conceptual Framework of Phosphatase Activity and Phosphorus Bioavailability

“…Their mutual relationship in mobilizing and mineralizing soil P o is shown to be synergistic in the conceptual model of Clarholm et al ( 2015 ). The bioavailability of P depends on the interaction of pH, phosphatase activity, and the concentration of LMWOAs in the soil solution (Adeleke et al, 2012 ). For example, a significant positive correlation was found between pH and phosphatase activity in the rhizosphere of drought-tolerant and non-drought-tolerant corn varieties under water stress (Song et al, 2012 ).…”

Microbial community structure and relationship with physicochemical properties of soil stockpiles in selected South African opencast coal mines

“…With regard to soil biological components, microbes and enzymes play several important roles in the soil ecosystem. Such roles include the mobilization of essential nutrients in the soil, mediation of plant nutrient uptake, plant-pathogen resistance, secretion of plant growthpromoting hormones and decomposition of soil organic matter (Tinker 1984;van Veen and Kuikman 1990;van der Heijden et al 2008;Adeleke et al 2012Adeleke et al , 2017. Hence, enzyme activities and diversity of microbes have been used as soil quality indices for ascertaining nutrient cycling and availability in the soil (Tabatabai and Dick 2002).…”

Review of Potential Microbial Effects on Flotation

“…These bacterial strains were shown to retrieve organic carbon directly from the bituminous black shale. Isolated bacterial strains from low-grade iron ores, classified as conglomerates and shale, from the Sishen mine in South Africa, were shown to belong to Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria [83]. The diversity of microorganisms inhabiting ores is likely much higher, because the majority of microorganisms in nature are not culturable on the media used in these studies.…”