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. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.

G. K. Suraishkumar

Department Of Biotechnology

Archanaa Sundararaghavan

Amitava Mukherjee

Gadi K Suraishkumar

Fulltext

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Environmental Science and Pollution Research

The key to sustainable and commercially viable biodiesel production relies primarily on species selection. Oleaginous species with high biomass productivity, lipid content, and lipid productivity are desirable. High growth rate of the species results in high biomass productivity, which leads to high lipid productivity. It is known that algal oil technology lacks commercial feasibility predominantly due to low biomass productivity and other factors. The use of a faster-growing organism, such as oleaginous bacteria, could offset this major disadvantage. Thus, the current study analyzes two model oleaginous systems: Rhodococcus opacus PD630 (a bacterium) and Chlorella vulgaris NIOT5 (a microalga) for their growth rate and lipid productivity. It was found that the bacterial growth rate was 25-fold the microalgal growth rate. The bacterium also showed 57-fold higher biomass productivity and 75-fold higher biodiesel productivity. Further, the analysis of a large number of literature data from relevant studies under different cultivation conditions showed that R. opacus PD630 has productivities far higher than various autotrophic microalgae. Similarly, a frequency distribution of data collected from the literature showed that Rhodococcus sp. has productivities in the higher range as compared to heterotrophic microalgae. Thus, bacteria could serve as a better alternative to microalgae toward developing a commercially viable biofuel technology. Further, the biodiesel characterization study showed that the quality of diesel from the bacterium was better than that from the microalga. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.

Bioenergy Research

Sustainable Diesel Feedstock: a Comparison of Oleaginous Bacterial and Microalgal Model Systems

Abstract The aim of the current study was to explore the different modes of the cytotoxicity effects of titania nanoparticles (TiO2 NPs) towards the dominant waste water isolate Exiguobacterium acetylicum at an exposure dose of ≤1 μg/mL in the sterilized and filtered waste water already containing 0.770 ± 0.02 μg/mL dissolved Ti4+ ions, under different conditions (UVA, Visible Light and Dark). The aggregation behaviour of TiO2 NPs in the experimental matrix was studied for 0.25, 0.5 and 1 μg/mL concentrations at different time intervals (0, 6 and 12 h). The reduction in cell viability under UVA was significantly more than that of other two conditions, i.e., dark and visible light. At 1 μg/mL of titania NPs for an exposure period of 6 h the cell viability with respect to control was found to be as follows: UVA (11.1 ± 0.33%) &lt;visible light (83.8 ± 1.3%) &lt;dark (84 ± 1.3%). The generation of oxidative stress (hydroxyl and superoxide radicals) was more in the bacterial cells exposed to UVA condition as compared to the cells exposed to visible light and dark condition. A significant increase in the membrane permeability was noted under UVA conditions in comparison to that in dark and visible light conditions. The fluorescence microscopy confirmed cell damage due to exposure to the nanoparticles. The scanning electron microscopy (SEM) analysis demonstrated the morphological distortion in the nanoparticle treated bacterial cells. The adsorption and further internalization of nanoparticles were confirmed by transmission electron microscopy (TEM) and elemental analysis. © 2015 Elsevier Ltd.

Journal of Environmental Chemical Engineering

Cytotoxicity of titania nanoparticles towards waste water isolate Exiguobacterium acetylicum under UVA, visible light and dark conditions

A challenge in algae-based bio-oil production is to simultaneously enhance specific growth rates and specific lipid content. We have demonstrated simultaneous increases in both the above in Chlorella vulgaris through reactive species (RS) induced under ultraviolet (UV) A and UVB light treatments. We postulated that the changes in photosystem (PS) stoichiometry and antenna size were responsible for the increases in specific growth rate. UVB treatment excited PSII, which resulted in a twofold to sevenfold increase in PSII/PSI ratio compared to control. An excited PSII caused a 2.7-fold increase in the specific levels of superoxide and a twofold increase in the specific levels of hydroxyl radicals. We have established that the increased specific intracellular RS (si-RS) levels increased the PSII antenna size by a significant 10-fold as compared to control. In addition, the 8.2-fold increase in specific lipid content was directly related to the si-RS levels. We have also demonstrated that the RS induced under UVA treatment led to a 3.2-fold increase in the saturated to unsaturated fatty acid ratio. Based on the findings, we have proposed and demonstrated a UV-based strategy, which achieved an 8.8-fold increase in volumetric lipid productivity. © 2013 American Institute of Chemical Engineers.

Biotechnology Progress

Simultaneous increases in specific growth rate and specific lipid content of Chlorella vulgaris through UV-induced reactive species

Scientific Reports

Features of diclofenac biodegradation by Rhodococcus ruber IEGM 346

Biotechnology for Biofuels

Characterization and optimization of endogenous lipid accumulation in Chlorella vulgaris SDEC-3M ability to rapidly accumulate lipid for reversing nightly lipid loss

Journal	Data powered by TypesetEnvironmental Science and Pollution Research
Publisher	Data powered by TypesetSpringer Verlag
ISSN	09441344
Open Access	No