Effect of Rhodococcus opacus PD630 on selenium phytoremediation by Brassica oleracea.

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-1 dry 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.

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.

Anaerobic digestion of aqueous phase from hydrothermal liquefaction of Spirulina using biostimulated sludge.

Hydrothermal liquefaction is a process that converts wet biomass into biofuels, more specifically bio-crude oil. During the process, post hydrothermal liquefaction waste water (PHWW) is generated, rich in nutrient and organic matter, however potentially toxic. Anaerobic digestion of PHWW from Spirulina, was evaluated using biostimulated sludge as a strategy to optimize the process. The biostimulation was conducted in a sequential batch reactor fed with organic acids and methanol aiming at development of acetogenic and methanogenic microorganism. Anaerobic biodegradability batch assays were performed, with biostimulated sludge and with non-biostimulated sludge, using increasing PHWW concentrations. Biostimulated sludge were more favourable for reaching higher methane yields at higher organic matter concentrations in comparison to non-biostimulated sludge, presenting less inhibition at conditions tested. Biostimulation was a key process to select and favour potential microorganisms involved in specialized uptake of recalcitrant compounds, such as Mesotoga and Methanomethylovorans.