Impact of nanotechnology in bioremediation

Impact of nanotechnology in bioremediation
Bioremediation is defined as “the process whereby the organic wastes are biologically degraded under controlled conditions to an innocuous state or levels below concentration limits established by regulatory authorities”. It is the process in which the micro-organisms or their enzymes are used to degrade the environmental contaminants to a less toxic form. The occurrence of bioremediation naturally is termed as intrinsic or attenuation bioremediation; whereas, the addition of fertilizers to enhance the bioavailability within the medium is termed as stimulated bioremediation. Moreover, bioremediation can be either in situ or ex situ. In in situ, the toxic waste is treated on its site with the use of indigenous micro-organisms while in ex situ, the contaminant is removed from its site and treated with exogenous micro-organisms. According to the US National Nanotechnology initiative, Environmental Improvement is one of the eight crosscutting areas of nanotechnology.

Preference of nanotechnology in bioremediation is due to:
  • The ability of nanoparticles to reach the contaminant zones where microparticles cannot.
  • Nanoparticles require less activation energy to obtain a feasible chemical reaction.
  • The surface plasmon resonance of nanoparticles can be used to detect toxic materials.
  • Higher reactivity is shown by the nanoparticles to redox-amenable contaminants.

  • The biggest challenge in bioremediation is increasing the solubility/bioavailability and hence the degradation rate. Currently, surfactant micelles are used to enhance the bioavailability of the contaminants. However, they breakdown when in contact with the soil and interact with liposomes of the micro-organism, thus limiting its efficacy. An increase in solubilisation of phenanthrene (PHEN) is seen upon using amphiphilic polyurethane (APU) nanoparticles. The nanoparticles are made up of polyurethane acrylic anionmer, precursor chains composed of hydrophobic interiors that have a high affinity for PHEN. By forming the nanoparticle-suspension, it increases the mobility and desorption of the compound. After being degraded by bacteria, the nanoparticles can be reused. The mobility of the APU nanoparticles in soil is determined by the charge density or the size of pendent hydrophilic chains that reside on the surface.

    Ferragels, zero valent iron nanoparticles, remove and immobilise Cr (IV) and Pb (II) from aqueous sources. They reduce Cr (IV) to Cr (III) and Pb (II) to Pb (0) by oxidising Fe to goethite. Moreover, to degrade halogen organic compounds, iron can be used to build a reactive wall in the path of the water source.

    To increase enzyme longevity, stability and reusability, enzymes are attached to the magnetic nanoparticles. To remove the enzymes from the substrate or products, a magnetic field can be applied to separate them out. This, in turn, enhances the activity of the enzymes and promotes reusability. Trypsin and peroxidase have been formed into a uniform core-shell magnetic nanoparticles. The nanoparticles shield the enzymes from oxidation.

    Advantages of nanotechnology include:
  • Nanoparticles can be used for remediation, sensing and detection, and pollution prevention.
  • Due to their small size and different surface coatings, nanoparticles can enter minute spaces, can be suspended in water for longer time, enabling them to travel farther and hence have better distribution.

  • Despite its various advantages, the main drawback of using nanoparticles is that, they undergo oxidation while reducing the contaminants. The oxidised nanoparticles cannot be reused.

    Nanotechnology offers an ecofriendly solution to toxic materials that are currently being used. Apart from catalysing the degradation of wastes and toxins (that are harmful to micro-organisms), nanoparticles enhance the activity of micro-organisms as well. The limiting factor in the commercialisation of nanoparticles for bioremediation is the safety issue. Toxicity tests are usually performed with pure nanoparticles on mammalian cells. The data collected from the tests cannot be used to determine the toxic effects of nanoparticles in environmental conditions. To identify the hazards caused by engineered nanomaterials, the US Environmental Protection Agency has issued a screening test. With further knowledge on the impact of nanoparticles on the environment and safety guidelines, nanotechnology will have a positive effect on environmental technology.

    How to cite this article:
    Sruthi Sritharan. Impact of nanotechnology in bioremediation. BioLim O-Media. 01 June, 2016. 4(6).
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