increased uranium bioprecipitation along with cobalt (Misra et al. 2012). Expressing
NiCoT gene into high radiation-resistant Deinococcus radiodurans through genetic
engineering showed increased uptake of radioactive Cobalt (
60 Co) isotope and
reduced the total biomass of cobalt (Gogada et al. 2015). Most of the bacteria of
Geobacteriaceae family are able to reduce radionuclides. The dcuB of Geobacter
sulfurreducens coded for fumarate transporter, constitutive expression of ducB in
G. metallireducens, increased respiratory capabilities along with bioremediation of
radioactive wastes (Butler et al. 2006). Genetic engineering holds considerable
promises, and more studies will require in developing advanced and more efficient
technologies for safe and clean environments.
13.3 Factors Affecting Bioremediation of Radioactive
Wastes
Microbes have the ability to adapt themselves with the changing environments and
showed a promising approach towards radioactive waste bioremediation. But there
are some biotic and abiotic factors which alters the biological processes of microbes
by altering the behaviour and growth. Lack of knowledge regarding the factors that
affect and influence may alter the rate of bioremediation (Boopathy 2000; Varjani
and Upasani 2017). Factors that affect the microbial processes are classified into
three groups:
1. Physicochemical factors or abiotic factors
2. Biological factors or biotic factors
3. Climatic factors
13.3.1 Physicochemical Factors or Abiotic Factors
The physicochemical factors that affect bioremediation by altering microbial behaviour and growth are mainly pH, solubility, presence and absence of electron donor
and acceptor, and the ionic strength. In the process of microbial biosorption, pH
plays the key role to absorb pollutants like radionuclides (Srivastava et al. 2014). A
slight change in pH may alter the rate of bioremediation. pH value changes cell
surface charge by altering the isoelectric points. The ionic strength of various ligands
like carboxylic group, phosphate groups, sulphur and amino groups directly depends
on pH (Boopathy 2000). Changes in pH value bring changes in ionic strength of such
ligands and alter the rate of biosorption. The solubility of metal ions are also pH
dependent as with decrease in pH the solubility of the metal ion increases which alter
the adsorption by microbial cells (Varjani and Upasani 2017). For examples, at pH 3
Mucor miehei sorbs 70–80 mg uranium/g dry weight of fungi, and at pH 4 and 5, the
biosorption increases 2–3 times, respectively (Gadd and Fomina 2011).
346
U. K. Vandana et al.
NiCoT gene into high radiation-resistant Deinococcus radiodurans through genetic
engineering showed increased uptake of radioactive Cobalt (
60 Co) isotope and
reduced the total biomass of cobalt (Gogada et al. 2015). Most of the bacteria of
Geobacteriaceae family are able to reduce radionuclides. The dcuB of Geobacter
sulfurreducens coded for fumarate transporter, constitutive expression of ducB in
G. metallireducens, increased respiratory capabilities along with bioremediation of
radioactive wastes (Butler et al. 2006). Genetic engineering holds considerable
promises, and more studies will require in developing advanced and more efficient
technologies for safe and clean environments.
13.3 Factors Affecting Bioremediation of Radioactive
Wastes
Microbes have the ability to adapt themselves with the changing environments and
showed a promising approach towards radioactive waste bioremediation. But there
are some biotic and abiotic factors which alters the biological processes of microbes
by altering the behaviour and growth. Lack of knowledge regarding the factors that
affect and influence may alter the rate of bioremediation (Boopathy 2000; Varjani
and Upasani 2017). Factors that affect the microbial processes are classified into
three groups:
1. Physicochemical factors or abiotic factors
2. Biological factors or biotic factors
3. Climatic factors
13.3.1 Physicochemical Factors or Abiotic Factors
The physicochemical factors that affect bioremediation by altering microbial behaviour and growth are mainly pH, solubility, presence and absence of electron donor
and acceptor, and the ionic strength. In the process of microbial biosorption, pH
plays the key role to absorb pollutants like radionuclides (Srivastava et al. 2014). A
slight change in pH may alter the rate of bioremediation. pH value changes cell
surface charge by altering the isoelectric points. The ionic strength of various ligands
like carboxylic group, phosphate groups, sulphur and amino groups directly depends
on pH (Boopathy 2000). Changes in pH value bring changes in ionic strength of such
ligands and alter the rate of biosorption. The solubility of metal ions are also pH
dependent as with decrease in pH the solubility of the metal ion increases which alter
the adsorption by microbial cells (Varjani and Upasani 2017). For examples, at pH 3
Mucor miehei sorbs 70–80 mg uranium/g dry weight of fungi, and at pH 4 and 5, the
biosorption increases 2–3 times, respectively (Gadd and Fomina 2011).
346
U. K. Vandana et al.