Effect of Rhodococcus opacus PD630 on selenium phytoremediation by Brassica oleracea

Abstract

The purpose of this study was to evaluate the potential of microbial-enhanced Brassica oleracea for the phytoremediation of seleniferous soils. The effect of selenite (Se(IV)) and selenate (Se(VI)) on B. oleracea (1–100 mg.L⁻¹) was examined through germination (7 d) and pot (30 d) trials. Microbial analysis was conducted to verify the toxic effect of various Se concentrations (1–500 mg.L⁻¹) on Rhodococcus opacus PD360, and to determine if it exhibits plant growth promoter traits. R. opacus PD630 was found to tolerate high concentrations of both Se(IV) and Se(VI), above 100 mg.L⁻¹. R. opacus PD630 reduced Se(IV) and Se(VI) over 7 days, with a Se conversion efficiency between 60 and 80%. Germination results indicated lower concentrations (0–10 mg.L⁻¹) of Se(IV) and Se(VI) gave a higher shoot length (> 4 cm). B. oleracea accumulated 600–1,000 mg.kg⁻¹dry weight (DW) of Se(IV) and Se(VI), making it a secondary accumulator of Se. Moreover, seeds inoculated with R. opacus PD360 showed increased Se uptake (up to 1,200 mg Se.kg⁻¹ DW). In addition, bioconcentration and translocation factors were greater than one. The results indicate a synergistic effect between R. opacus PD630 and B. oleracea for Se phytoextraction from polluted soils.

NOVELTY STATEMENT

This article examines how Brassica oleracea may be used to improve seleniferous soils and how Rhodococcus opacus can be added to increase biofortification. The research shows great potential for combining Brassica species with bacterial isolates to remove selenium from heavily contaminated soils.

Keywords:

• Phytoextraction
• plant growth promotion
• seleniferous soil

Acknowledgments

The authors thank Borja Khatabi Soliman Tamayo, Leah Egan, and Manuel Suarez (National University of Ireland, Galway) for their technical support.

Additional information

Funding

This work was supported by the Science Foundation Ireland (SFI) through the SFI Research Professorship Programme Innovative Energy Technologies for Biofuels, Bioenergy and a Sustainable Irish Bioeconomy (IETSBIO³; grant number 15/RP/2763) and the Research Infrastructure research grant Platform for Biofuel Analysis (Grant Number 16/RI/3401).