Investigating the potential use of an oleaginous bacterium, Rhodococcus opacus PD630, for nano-TiO2 remediation.

Abstract

The occurrence of titanium dioxide nanoparticles (nTiO2), in the effluents released from wastewater treatment plants, has raised concerns. The fate of nTiO2 and their potential impact on organisms from different ecosystems are widely investigated. For the first time, in this work, we report the responses of an oleaginous bacteria Rhodococcus opacus PD630, belonging to an ecologically important genus Rhodococcus to environmentally relevant concentrations of nTiO2, under dark and UV light conditions. We observed a dose-dependent increase in nTiO2 uptake by the bacteria that reached a maximum of 1.4 mg nTiO2 (g cell)-1 under mid-log UV exposure, corresponding to 97% uptake. The nTiO2 induced oxidative stress in bacteria that increased from 25.1 to a maximum of 100.3, 44.1, and 51.7 μmol.OH (g cell)-1 under dark, continuous, and mid-log UV, respectively. However, nTiO2 did not affect bacterial viability. Further, due to oxidative stress, the triacylglycerol (biodiesel) content from bacteria increased from 30% to a maximum of 54% CDW. Based on our findings, we propose an application of R. opacus PD 630 in nTiO2 remediation due to their high nTiO2 uptake and resistance.