microbial activity like biotransformation, biomineralization and biosorption and
bioaccumulation (Fig. 13.1) can reduce the toxicity of radioactive wastes and also
increase the metal transport into the microbial system (Valdovinos et al. 2017;
Kumar et al. 2007).
13.2.1 Bacterial Bioremediation of Radioactive Wastes
There are a huge number of bacteria that have the ability to remediate pollutants like
metallic compounds and other organic pollutants through detoxification, transformation or immobilization. But, all the bacteria are not able to resist under high
ionizing radiation and high acidic conditions (Misra et al. 2012). The waste produced
from atomic power plants, nuclear weapon testing sites, mining and medical research
industries contains actinides (Marra and Palmer 2011). Radioactivity is one of the
most important property of actinides. Actinides and other fission products present in
the wastes are able to produce high amount of β-radiation and γ-radiation. Therefore,
the use of extremophilic bacteria which are able to resist under high radiations is an
essential requirement for bioremediation under such extremophilic conditions
(Albrecht-Schmitt 2019; Misra et al. 2012). Several microbial processes are involved
in bioremediation of pollutants, but biotransformation, biomineralization,
biosorption and bioaccumulation processes are most important bioremediation processes for radioactive wastes (Table 13.1, Kumar et al. 2007).
13.2.1.1 Biotransformation via Bioreduction
One of the most important negative properties of metals or other radioactive metallic
waste element is that the elements cannot be destroyed like other organic pollutants,
but it can transform or convert one form to another (Ayangbenro and Babalola
2017). Initially, the radioactive wastes are present in either soluble or insoluble form,
and after disposal, the microbial process may convert the wastes soluble to insoluble
or vice versa. This strategy of microbial process is used in the field of bioremediation
(Francis 2006). The presence of electron acceptor like oxygen and electron donor
like hydrogen influences the biotransformation. In the absence of oxygen, i.e. under
anaerobic condition, bacteria use nitrates, sulphates or carbon dioxide as electron
acceptor (Francis 2006; El Mamouni et al. 2002). Bacteria can transform radionuclides by either direct or indirect mechanisms.
1. Direct immobilization of radionuclides
Direct immobilization of radionuclides includes transformation of radionuclides by enzymatic processes produced by microbes (Kumar et al. 2007).
Actinides like Uranium (U), Technetium (Tc), Chromium (Cr), etc. showed
efficient enzymatic reduction by microbes. In aqueous condition, oxidized form
of actinides like Uranium (U), Technetium (Tc), Chromium (Cr), etc. is present in
338
U. K. Vandana et al.
bioaccumulation (Fig. 13.1) can reduce the toxicity of radioactive wastes and also
increase the metal transport into the microbial system (Valdovinos et al. 2017;
Kumar et al. 2007).
13.2.1 Bacterial Bioremediation of Radioactive Wastes
There are a huge number of bacteria that have the ability to remediate pollutants like
metallic compounds and other organic pollutants through detoxification, transformation or immobilization. But, all the bacteria are not able to resist under high
ionizing radiation and high acidic conditions (Misra et al. 2012). The waste produced
from atomic power plants, nuclear weapon testing sites, mining and medical research
industries contains actinides (Marra and Palmer 2011). Radioactivity is one of the
most important property of actinides. Actinides and other fission products present in
the wastes are able to produce high amount of β-radiation and γ-radiation. Therefore,
the use of extremophilic bacteria which are able to resist under high radiations is an
essential requirement for bioremediation under such extremophilic conditions
(Albrecht-Schmitt 2019; Misra et al. 2012). Several microbial processes are involved
in bioremediation of pollutants, but biotransformation, biomineralization,
biosorption and bioaccumulation processes are most important bioremediation processes for radioactive wastes (Table 13.1, Kumar et al. 2007).
13.2.1.1 Biotransformation via Bioreduction
One of the most important negative properties of metals or other radioactive metallic
waste element is that the elements cannot be destroyed like other organic pollutants,
but it can transform or convert one form to another (Ayangbenro and Babalola
2017). Initially, the radioactive wastes are present in either soluble or insoluble form,
and after disposal, the microbial process may convert the wastes soluble to insoluble
or vice versa. This strategy of microbial process is used in the field of bioremediation
(Francis 2006). The presence of electron acceptor like oxygen and electron donor
like hydrogen influences the biotransformation. In the absence of oxygen, i.e. under
anaerobic condition, bacteria use nitrates, sulphates or carbon dioxide as electron
acceptor (Francis 2006; El Mamouni et al. 2002). Bacteria can transform radionuclides by either direct or indirect mechanisms.
1. Direct immobilization of radionuclides
Direct immobilization of radionuclides includes transformation of radionuclides by enzymatic processes produced by microbes (Kumar et al. 2007).
Actinides like Uranium (U), Technetium (Tc), Chromium (Cr), etc. showed
efficient enzymatic reduction by microbes. In aqueous condition, oxidized form
of actinides like Uranium (U), Technetium (Tc), Chromium (Cr), etc. is present in
338
U. K. Vandana et al.