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The effect of heavy metals on thiocyanate biodegradation by an autotrophic microbial consortium enriched from mine tailings.

ABSTRACT: Bioremediation systems represent an environmentally sustainable approach to degrading industrially generated thiocyanate (SCN^-), with low energy demand and operational costs and high efficiency and substrate specificity. However, heavy metals present in mine tailings effluent may hamper process efficiency by poisoning thiocyanate-degrading microbial consortia. Here, we experimentally tested the tolerance of an autotrophic SCN^--degrading bacterial consortium enriched from gold mine tailings for Zn, Cu, Ni, Cr, and As. All of the selected metals inhibited SCN^- biodegradation to different extents, depending on concentration. At pH of 7.8 and 30 °C, complete inhibition of SCN^- biodegradation by Zn, Cu, Ni, and Cr occurred at 20, 5, 10, and 6 mg L^-1, respectively. Lower concentrations of these metals decreased the rate of SCN^- biodegradation, with relatively long lag times. Interestingly, the microbial consortium tolerated As even at 500 mg L^-1, although both the rate and extent of SCN^- biodegradation were affected. Potentially, the observed As tolerance could be explained by the origin of our microbial consortium in tailings derived from As-enriched gold ore (arsenopyrite). This study highlights the importance of considering metal co-contamination in bioreactor design and operation for SCN^- bioremediation at mine sites. KEY POINTS: • Both the efficiency and rate of SCN^- biodegradation were inhibited by heavy metals, to different degrees depending on type and concentration of metal. • The autotrophic microbial consortium was capable of tolerating high concentrations of As, potential having adapted to higher As levels derived from the tailings source.

SUBMITTER: Shafiei F

PROVIDER: S-EPMC7778618 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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The effect of heavy metals on thiocyanate biodegradation by an autotrophic microbial consortium enriched from mine tailings.

Shafiei Farhad F Watts Mathew P MP Pajank Lukas L Moreau John W JW

Applied microbiology and biotechnology 20201202 1

Bioremediation systems represent an environmentally sustainable approach to degrading industrially generated thiocyanate (SCN<sup>-</sup>), with low energy demand and operational costs and high efficiency and substrate specificity. However, heavy metals present in mine tailings effluent may hamper process efficiency by poisoning thiocyanate-degrading microbial consortia. Here, we experimentally tested the tolerance of an autotrophic SCN<sup>-</sup>-degrading bacterial consortium enriched from go ...[more]

PMID: 33263791

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Project description:Thiocyanate (SCN- ) is a toxic compound that forms when cyanide (CN- ), used to recover gold, reacts with sulfur species. SCN- -degrading microbial communities have been studied, using bioreactors fed synthetic wastewater. The inclusion of suspended solids in the form of mineral tailings, during the development of the acclimatized microbial consortium, led to the selection of an active planktonic microbial community. Preliminary analysis of the community composition revealed reduced microbial diversity relative to the laboratory-based reactors operated without suspended solids. Despite minor upsets during the acclimation period, the SCN- degradation performance was largely unchanged under stable operating conditions. Here, we characterized the microbial community in the SCN- degrading bioreactor that included solid particulate tailings and determined how it differed from the biofilm-based communities in solids-free reactor systems inoculated from the same source. Genome-based analysis revealed that the presence of solids decreased microbial diversity, selected for different strains, suppressed growth of thiobacilli inferred to be primarily responsible for SCN- degradation, and promoted growth of Trupera, an organism not detected in the reactors without solids. In the solids reactor community, heterotrophy and aerobic respiration represent the dominant metabolisms. Many organisms have genes for denitrification and sulfur oxidation, but only one Thiobacillus sp. in the solids reactor has SCN- degradation genes. The presence of the solids prevented floc and biofilm formation, leading to the observed reduced microbial diversity. Collectively the presence of the solids and lack of biofilm community may result in a process with reduced resilience to process perturbations, including fluctuations in the influent composition and pH. The results from this investigation have provided novel insights into the community composition of this industrially relevant community, giving potential for improved process control and operation through ongoing process monitoring.

Dataset Information

The effect of heavy metals on thiocyanate biodegradation by an autotrophic microbial consortium enriched from mine tailings.

Publications

The effect of heavy metals on thiocyanate biodegradation by an autotrophic microbial consortium enriched from mine tailings.

Similar Datasets

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