detoxification is one of the major strategies in the bioaccumulation of metal ions
from the dye effluents. This cytoplasmic detoxification is achieved by carrying the
dye pollutants external to the cell or to less subtle cellular compartments, thus
making the pollutants not available for stimulating the cytotoxic effects. Living
biomass may develop strategies such as metal efflux, intracellular chelation by
metallothionein protein and phytochelation, and metal compartmentalization in
vacuoles for the detoxification, but the exact mechanism of intracellular accumulation is still not explained (Tamás and Wysocki 2010; Kamizono et al. 1989; Kneer
et al. 1992; Presta and Stillman 1997).
Studies conducted on the investigation of the mechanism involved in metal
detoxification process confirm the importance of vacuole in the detoxification of
pollutants from the industrial effluents. The detoxification process is achieved by one
or a combination of the processes such as biological degradation, storing of metabolites, and control of cytosolic concentrations of pollutants. Studies showed that the
cells having lower vacuoles were highly sensitive to environmental conditions and
had less metal removal capacities (Ramsay and Gadd 1997; Thorsen et al. 2012).
Bioaccumulation process is governed by the structural, physical, and biological
properties, genetic mutations, population of the living organisms, and also concentration of pollutants. The growth of living cells depends on the composition of
the growth medium, pH, temperature, and presence of other pollutants, inhibitors,
surfactants, etc. The mechanism involved in the bioaccumulation process is also
influenced by various metabolic activities of the organisms such as respiration,
metabolite release, nutrient intake, etc. (Gadd 2009; Kujan et al. 1995).
4.3 Biosorption and Bioaccumulation
In both biosorption and bioaccumulation methods, pollutants or contaminants transfer from the environment to the surface of the microorganism or biomass. In
biosorption, contaminants adsorb onto the biomass cell wall surface. The rate of
adsorption depends on the cell composition, cell wall structure, and kinetics of the
process. Biosorption is a passive process and does not require any energy/respiration, whereas bioaccumulation is an active metabolic process and requires energy
and respiration. In biosorption, pollutants adsorb on the cellular surface mostly by
a physical process; hence, it may be reversible. On the other hand, bioaccumulation
is partially reversible; moreover, biosorption process is fast compared to the
bioaccumulation (Vijayaraghavan and Yun 2008; Velásquez and Dussan 2009).
Several studies reported that bioaccumulation process is more effective in the
removal of metal ions present in the dyes compared to biosorption. However,
the biosorption process is very attractive and economically feasible in large-scale
applications compared to bioaccumulation process since the bioaccumulation process requires the close control of the growth of living organisms that are very
complex, costly, and difficult. Moreover, wide varieties of biosorbents are able to
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N. S. KV
from the dye effluents. This cytoplasmic detoxification is achieved by carrying the
dye pollutants external to the cell or to less subtle cellular compartments, thus
making the pollutants not available for stimulating the cytotoxic effects. Living
biomass may develop strategies such as metal efflux, intracellular chelation by
metallothionein protein and phytochelation, and metal compartmentalization in
vacuoles for the detoxification, but the exact mechanism of intracellular accumulation is still not explained (Tamás and Wysocki 2010; Kamizono et al. 1989; Kneer
et al. 1992; Presta and Stillman 1997).
Studies conducted on the investigation of the mechanism involved in metal
detoxification process confirm the importance of vacuole in the detoxification of
pollutants from the industrial effluents. The detoxification process is achieved by one
or a combination of the processes such as biological degradation, storing of metabolites, and control of cytosolic concentrations of pollutants. Studies showed that the
cells having lower vacuoles were highly sensitive to environmental conditions and
had less metal removal capacities (Ramsay and Gadd 1997; Thorsen et al. 2012).
Bioaccumulation process is governed by the structural, physical, and biological
properties, genetic mutations, population of the living organisms, and also concentration of pollutants. The growth of living cells depends on the composition of
the growth medium, pH, temperature, and presence of other pollutants, inhibitors,
surfactants, etc. The mechanism involved in the bioaccumulation process is also
influenced by various metabolic activities of the organisms such as respiration,
metabolite release, nutrient intake, etc. (Gadd 2009; Kujan et al. 1995).
4.3 Biosorption and Bioaccumulation
In both biosorption and bioaccumulation methods, pollutants or contaminants transfer from the environment to the surface of the microorganism or biomass. In
biosorption, contaminants adsorb onto the biomass cell wall surface. The rate of
adsorption depends on the cell composition, cell wall structure, and kinetics of the
process. Biosorption is a passive process and does not require any energy/respiration, whereas bioaccumulation is an active metabolic process and requires energy
and respiration. In biosorption, pollutants adsorb on the cellular surface mostly by
a physical process; hence, it may be reversible. On the other hand, bioaccumulation
is partially reversible; moreover, biosorption process is fast compared to the
bioaccumulation (Vijayaraghavan and Yun 2008; Velásquez and Dussan 2009).
Several studies reported that bioaccumulation process is more effective in the
removal of metal ions present in the dyes compared to biosorption. However,
the biosorption process is very attractive and economically feasible in large-scale
applications compared to bioaccumulation process since the bioaccumulation process requires the close control of the growth of living organisms that are very
complex, costly, and difficult. Moreover, wide varieties of biosorbents are able to
184
N. S. KV