Elsevier

Chemosphere

Volume 156, August 2016, Pages 228-235
Chemosphere

Bioremediation of lead contaminated soil with Rhodobacter sphaeroides

https://doi.org/10.1016/j.chemosphere.2016.04.098Get rights and content

Highlights

  • Rhodobacter sphaeroides showed a certain remediation effect on Pb-contaminated soil.

  • More available fractions were transformed to less accessible and inert fractions.

  • Pb phytoavailability was reduced in amended soils.

Abstract

Bioremediation with microorganisms is a promising technique for heavy metal contaminated soil. Rhodobacter sphaeroides was previously isolated from oil field injection water and used for bioremediation of lead (Pb) contaminated soil in the present study. Based on the investigation of the optimum culturing conditions and the tolerance to Pb, we employed the microorganism for the remediation of Pb contaminated soil simulated at different contamination levels. It was found that the optimum temperature, pH, and inoculum size for R. sphaeroides is 30–35 °C, 7, and 2 × 108 mL−1, respectively. Rhodobacter sphaeroides did not remove the Pb from soil but did change its speciation. During the bioremediation process, more available fractions were transformed to less accessible and inert fractions; in particular, the exchangeable phase was dramatically decreased while the residual phase was substantially increased. A wheat seedling growing experiment showed that Pb phytoavailability was reduced in amended soils. Results inferred that the main mechanism by which R. sphaeroides treats Pb contaminated soil is the precipitation formation of inert compounds, including lead sulfate and lead sulfide. Although the Pb bioremediation efficiency on wheat was not very high (14.78% root and 24.01% in leaf), R. sphaeroides remains a promising alternative for Pb remediation in contaminated soil.

Introduction

Lead (Pb) contamination in soil is one of the major public concerns in recent years, as Pb can accumulate in plant or human body leading to irreversible damage to human health, especially for children. Such damage includes impaired development, reduced intelligence, short-term memory loss, disabilities in learning and coordination problems, and risk of cardiovascular disease (Dixit et al., 2015). Heavy metal contamination in soil can be remediated through various mobilization and immobilization techniques (Fan et al., 2012). Compared with physicochemical methods, biotechnological approaches are gaining increasing prominence in the remediation of a variety of environmental matrices because they are cost effective, environmentally friendly, and are associated with fewer side effects. They have therefore emerged as potentially useful alternative technologies for restoring contaminated sites and removing contaminants from the environment (Dhankhar and Hooda, 2011, Mani and Kumar, 2013, Merugu et al. 2014, Aryal and Liakopoulou-Kyriakides, 2015, Dixit et al., 2015, Fonti et al., 2015).

A wide variety of microorganisms (fungi, algae, bacteria, etc.) are already used as tools for heavy metal bioremediation, whose mechanisms mainly include valence transformation, volatilization and extracellular chemical precipitation (Wu et al., 2010, Marques et al., 2011). Rhodobacter sphaeroides is a Gram-negative, phototropic purple non-sulfur bacterium exhibiting several metabolic pathways depending on the growth conditions (Calvano et al., 2014). This versatile bacterium has drawn considerable attention in energy and environment researches; for example, it has been reported to be important in hydrogen production and photobioelectrochemical fuel cell development (Zhu et al., 2002, Rosenbaum et al., 2005, Hakobyan et al., 2012). In addition, it has been widely applied to treat wastewater because of its strong survivability under abiotic stress conditions and high tolerance to carbon starvation (Kanno et al., 2014), herbicides (Zhang et al., 2012), salt (Panwichian et al., 2010b), heavy metals (Buccolieri et al., 2006, Giotta et al., 2006, Panwichian et al., 2011, Volpicella et al., 2014), and organic and eutrophication (Nagadomi et al., 2000, Kim et al., 2004, Kantachote et al., 2005, Takeno et al., 2005, Madukasi et al., 2010, Merugu et al. 2014). The R. sphaeroides strains had been used to degrade various contaminants from soil and sediment mud, such as phosphorus, atrazine, salts and radionuclide (cesium), whilst the removal efficiency, impacting factors and mechanisms of which had also been discussed (Takeno et al., 1999, Du et al., 2011, Panwichian et al., 2012, Sasaki et al., 2012a, Sasaki et al., 2012b). However, the studies concentrated on bioremediation of heavy metal in soil using R. sphaeroides has rarely been reported. Fan et al. (2012) and Panwichian et al. (2012) had used the strain to remove heavy metals from soil and sediment mud, respectively, and plant growth experiments were performed to evaluate the phytotoxicity after bioremediation. But, the bioremediation mechanism for heavy metal contaminated soil has not been well understood until now.

R. sphaeroides had been employed to remedy cadmium (Cd) contaminated soil in our former research (Fan et al., 2012), which concluded that the bacterium could redistribute the geo-speciation of Cd and reduce the Cd phytoavailability in amended soils. In addition, it was noticed that the geo-speciation of Pb also changed remarkably during the bioremediation process. Thus, in this paper, we further investigate the optimum culturing condition of R. sphaeroides and its tolerance to Pb. The remediation efficiency and mechanisms are also discussed in details.

Section snippets

Isolation and identification of R. sphaeroides

The strain isolated from the oil field injection water in DaQing was identified as R. sphaeroides (Fan et al., 2012). Postgate C liquid medium was selected as the culture medium for R. sphaeroides (Postgate, 1979). The culture medium was prepared with oil field injection water. Optical density at 420 nm (OD420) measured by an ultraviolet–visible spectrophotometer (UV-754) was examined for cell counting because a significant positive correlation (r = 0.9850, p < 0.01) was obtained between OD420

Optimum culturing conditions and Pb tolerance of R. sphaeroides

Influences of temperature, pH, and inoculum size on the growth of R. sphaeroides are shown in Fig. 1a–c, respectively. It was found that the influences of temperature, pH, and inoculum size on the growth of R. sphaeroides had similar curves; they increased at first and then decreased over time. The maximum biomass was obtained at T = 35 °C, pH = 7, and inoculum size = 2 × 108 mL−1, but the high biomass was also observed at T = 30 °C. Thus, the optimum temperature was 30–35 °C and the optimum pH

Conclusions

In present study, R. sphaeroides was used for bioremediation of Pb contaminated soils. Optimum culturing conditions of the strain were firstly investigated, and results showed that the optimum culturing conditions of R. sphaeroides were pH = 7, T = 30–35 °C, with the inoculum size of 2 × 108 mL−1. Then, the bioremediation experiments were conducted under these conditions. It was found that, during soils bioremediation, R. sphaeroides did not decrease the total content of Pb in soil but could

Acknowledgments

This work was supported by the National Natural Science Foundation of China (51178019, 51290283 and 51378041), Beijing Natural Science Foundation (8142027), Specialized Research Fund for the Doctoral Program of Higher Education (20131102110035), and Major Science and Technology Program for Water Pollution Control and Treatment of China (2012ZX07501001).

References (53)

  • K. Takeno et al.

    Removal of phosphorus from oyster farm mud sediment using a photosynthetic bacterium, Rhodobacter sphaeroides IL106

    J. Biosci. Bioeng.

    (1999)
  • G. Wu et al.

    A critical review on the bio-removal of hazardous heavy metals from contaminated soils: issues, progress, eco-environmental concerns and opportunities

    J. Hazard. Mater.

    (2010)
  • Y. Zhang et al.

    Oxidative stress response in atrazine-degrading bacteria exposed to atrazine

    J. Hazard. Mater.

    (2012)
  • H. Zhu et al.

    Hydrogen production as a novel process of wastewater treatment—studies on tofu wastewater with entrapped R. sphaeroides and mutagenesis

    Int. J. Hydrogen Energy

    (2002)
  • M. Aryal et al.

    Bioremoval of heavy metals by bacterial biomass

    Environ. Monit. Assess.

    (2015)
  • A. Badarudeen et al.

    Texture and geochemistry of the sediments of a tropical mangrove ecosystem, southwest coast of India

    Environ. Geol.

    (1996)
  • H. Bai et al.

    Biological synthesis of size-controlled cadmium sulfide nanoparticles using immobilized Rhodobacter sphaeroides

    Nanoscale Res. Lett.

    (2009)
  • H. Bai et al.

    Toxic effects of Pb2+, Cd2+ and Cr(Ⅵ) on inhibition of Rhodobacter sphaeroides growth

    Chin. J. Appl. Environ. Biol.

    (2006)
  • H. Bai et al.

    Study on transformation and removal of the heavy metal cadmium by Rhodobacter sphaeroides

    Acta Sci. Circumstantiae

    (2006)
  • H. Bai et al.

    Studies on removal and transformation mechanism of lead by Rhodobacter sphaeroides

    Acta Sci. Circumstantiae

    (2007)
  • A. Buccolieri et al.

    Testing the photosynthetic bacterium Rhodobacter sphaeroides as heavy metal removal tool

    Ann. Chim.

    (2006)
  • C.D. Calvano et al.

    The lipidome of the photosynthetic bacterium Rhodobacter sphaeroides R26 is affected by cobalt and chromate ions stress

    Biometals Int. J. Role Metal Ions Biol. Biochem. Med.

    (2014)
  • C. Delmas et al.

    Mobility and adsorption capacity of Pb and Zn in a polluted soil from a road environment: laboratory batch experiments

    Environ. Technol.

    (2002)
  • R. Dhankhar et al.

    Fungal biosorption–an alternative to meet the challenges of heavy metal pollution in aqueous solutions

    Environ. Technol.

    (2011)
  • R. Dixit et al.

    Bioremediation of heavy metals from soil and aquatic environment: an overview of principles and criteria of fundamental processes

    Sustainability

    (2015)
  • P. Du et al.

    Distribution of Cd, Pb, Zn and Cu and their chemical speciations in soils from a peri-smelter area in northeast China

    Environ. Geol.

    (2008)
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