Abstract
It is well known that the culture conditions of microorganisms may affect their surface properties, zeta potential and hydrophobicity via the modification of the cell wall functional groups or metabolic products. The R. opacus bacteria strain was separately adapted to the presence of apatite and quartz, after which a cellular adaptation procedure was developed by repeated sub-culturing with a successive increase in the mineral content. Zeta potential, surface tension, FTIR and microflotation studies were used to evaluate the behavior of the cells that were developed under defined culture conditions. The cellular adaptation induced a modification of the bacterial surface charge. The FTIR results showed a modification of its functional groups. The surface tension results suggested that longer growing time promoted a higher production of metabolites. The use of mineral-adapted cells promoted an improvement in the flotability of both minerals, but it was more significant for apatite flotation. Additionally, the mineral flotability remained unchanged when the cells developed under a longer culture time. Nevertheless, there was a reduction in the surface tension.
Highlights
Studies on the application of biotechnology in mineral processing have intensified in recent years
Any changes in the cell surface charge may be related to modifications in the bacterial cell wall functional groups
The zeta potential evaluation of the R. opacus before and after adaptation to the presence of a mineral substrate showed that the bacterial cells modified its zeta potential profiles; no significant change was observed with higher culture times
Summary
Studies on the application of biotechnology in mineral processing have intensified in recent years. Quite recently used in mineral bioflotation, is Rhodococcus opacus (Botero et al, 2007; Mesquita et al, 2003; Botero et al, 2008; Merma et al, 2013). It is a Gram positive bacterium with different types of components on their cell-wall, which are primarily polysaccharides, carboxylic acids, lipid groups and mycolic acids, that result in amphoteric behavior (hydrophobic and/or hydrophilic properties) of the bacteria (Mesquita et al, 2003; Natarajan, 2006; Vilinska and Rao., 2008). To our knowledge, there is no study on the cellular adaptation of R. opacus bacteria to a mineral substrate
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