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. 2021 Jan;105(1):417-427.
doi: 10.1007/s00253-020-10983-4. Epub 2020 Dec 2.

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

Farhad Shafiei  1 , Mathew P Watts  1 , Lukas Pajank  1 , John W Moreau  2   3
Affiliations

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

Farhad Shafiei et al. Appl Microbiol Biotechnol. 2021 Jan.

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.

Keywords: Bioremediation; Geomicrobiology; Gold mining; Metal tolerance; Metal toxicity.

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Conflict of interest statement

The authors declare that they have no conflict of interest.

Figures

Fig. 1
Fig. 1
Effect of Zn amendment on microbial SCN− degradation; results represent mean ± standard deviation, n = 3
Fig. 2
Fig. 2
Effect of Cu amendment on microbial SCN− degradation; results represent mean ± standard deviation, n = 3
Fig. 3
Fig. 3
Effect of Ni amendment on microbial SCN− degradation; results represent mean ± standard deviation, n = 3
Fig. 4
Fig. 4
Effect of Cr amendment on microbial SCN− degradation; results represent mean ± standard deviation, n = 3
Fig. 5
Fig. 5
Effect of As amendment on microbial SCN− degradation; results represent mean ± standard deviation, n = 3
See this image and copyright information in PMC

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