Adhesion abilities and biosorption of Cd and Mg by microorganisms - first step for eco-friendly beneficiation of phosphate ore

Abstract

Chemical reagents used in traditional mineral processing can be toxic and hazardous for the environment. Therefore, the use of biotechnological methods is becoming increasingly important. Great hopes are being placed in the use of microorganisms for bio-beneficiation of raw materials. However, assessment of adhesion abilities of bacteria onto minerals surface as well as biosorption of metals are essential steps before designing final process of each ore beneficiation. The main aim of this work was an investigation of biosorption of Cd and Mg, as well as adhesion abilities of five microorganism species with minerals included in the natural mixture of phosphate ore form Djebel Onk, Algeria. The ore, due to its unique composition, created conditions for adhesion of all five tested microbial strains onto apatite surface during incubation at pH 3. Moreover, Rhodococcus erythropolis CD 130, Pseudomonas fluorescens and Escherichia coli adhered distinctly onto apatite surface during incubation at pH 7. Incubation lasting 20 min at pH 4-6 created the most favorable conditions for biosorption of metals by B. subtilis and adhesion of cells. In case of C. albicans, biosorption of metals as well as adhesion of cells onto the mineral surface were more effective after longer time and in a wider pH range.

Mg and Cd biosorption by native bacteria form Djebel Onk mine (Algeria)

“…Compared to the bacteria used in our previous study 15 , Cd (and Mg) concentrations in native bacteria were much higher. The most effective strain, Bacillus sp.…”

“…Compared to the values obtained for B. subtilis USK1 from the collection of the University of Silesia in Katowice 15 , these values are much higher. In that study, Mg accumulation in the biomass of microorganisms stayed in a range from 324 to 2698 µg Mg g -1 and was higher at pH 7 than at pH 3 15 , emphasizing the high potential of native species for biotechnology. Accumulation of signi cant amounts of Mg is highly important because it helps removing unwanted Mg from phosphate ores, and it could be useful in reclaiming this element from waste and recycling it.…”

“…In 2019, we conducted the rst attempts of using bacteria to purify phosphate ores from Djebel Onk 15 . In that research, we selected ve species from the collection of the University of Silesia in Katowice: B. subtilis, Rhodococcus erythropolis CD 130, Pseudomonas uorescens, Escherichia coli and Candida albicans.…”

“…It seemed that B. subtilis and C. albicans were the most promising microorganisms in the context of biosorption; therefore, we decided to focus on them. We also suspected that Cd concentration in the studied ore samples (and consequently in the incubating solution) was not very high, and the biomass used was enough to remove the vast majority, if not all of Cd washed out during incubation 15 . Recent studies conducted with native bacteria do not fully con rm our earlier suspicions and shed new light on designing new, environmentally friendly methods of treating phosphate ores.…”

“…Most of these species, which exhibit outstanding biosorption capabilities, were isolated from speci c, highly contaminated environments. Long-term exposure to strong stress factors stimulates those bacteria to develop and reinforce their unique properties, which enable them to bind substantial amounts of metals 1,12−24 . This study is a continuation of our earlier work, where we analyzed the metal biosorption abilities of ve bacterial species from the collection of the University of Silesia in Katowice after incubation with phosphate ore from Djebel Onk 15 . These organisms did not originate from heavy metal contaminated sites and did not exhibit any exceptional capabilities of biosorption.…”