(Gianfreda and Bollag 2002). All the metabolic reactions in living organisms
especially microorganisms are mediated by enzymes and the techniques that use
enzymes are environmentally friendly processes, therefore such characteristics make
them eco-friendly catalysts (Rao et al. 2010; Abatenh et al. 2017). All metabolic
enzymes belong to the group of hydrolases, lyases, transferases, oxidoreductases,
ligases and isomerases (Abatenh et al. 2017). Enzymes are biocatalysts that help in
the facilitation of transformation of reactants into products by the provision of
positive conditions to lessen the activation energy during reaction found universally
in all living organisms (Ahuja et al. 2004; Karigar and Rao 2011). Enzymes are not
expensive and catalysts that are friendly to nature with the capability of
bioremediating the many harmful compounds that are not friendly to our environment as per studied present scenario of societal ecological standards (Rao et al. 2010;
Karigar and Rao 2011).
Structurally an enzyme is a protein that consists of one polypeptide moiety, and
the part of these biocatalysts that actively takes part in the catalytic processes is
known as active sites. These biocatalysts have one or more groups that are necessary
for their catalytic activity, associated with the active sites, either by covalent or by
other bonds; this protein part in such enzymes is called apoenzyme. On the other
hand, the non-protein part is generally called as the prosthetic group. Both apoenzyme and prosthetic groups combine to form holoenzyme (Karigar and Rao 2011).
The action of enzymes may be intracellular, i.e. on the inner side of the cells from
where they are originated or act extracellularly, i.e. in the absence of cells of their
origination. If the enzyme is presently free, i.e. insoluble form, this type of catalysis
is known as homogenous, or immobilized; on the other hand, if the enzyme is linked
through a solid matrix, then catalysis is called as heterogeneous. The main producers
of these catalysts are generally white-rot fungi, bacteria, and microbe-plant
associations (Rao et al. 2010). The extracellular enzymes produced by fungi especially filamentous fungi is paramount because it is primarily utilized bioremediating
or neutralizing toxic contaminants, for instance, polycyclic aromatic hydrocarbons
(PAHs), which is a primary toxic pollutant that poses a potential risk to human health
(Bonugli-Santos et al. 2010).
Enzyme-based degradation process usually occurs at a faster rate than abiotic
oxidation reactions as well as organic chemical pollutants that moves into the
metabolic pathway carried out by microbes present in the soil. The reason behind
this enzyme-based reaction is the free energy potential which is being used by the
microbes for degradation processes (Jonsson and Haller 2014). Table 15.1 shows
various enzymes produced by various microorganisms and the substrate they act
upon for degradation. The development of enzymes for the process of remediation
usually done in three steps mentioned below:
(i) Isolation and identification of template enzyme from the natural resources.
(ii) Isolation of the genes that encode for a particular enzyme.
(iii) Improvement of enzymatic efficiency by improving enzyme properties in the
laboratory (Sutherland et al. 2004).
15 The Role of Microorganisms in Remediation of Environmental Contaminants
437
especially microorganisms are mediated by enzymes and the techniques that use
enzymes are environmentally friendly processes, therefore such characteristics make
them eco-friendly catalysts (Rao et al. 2010; Abatenh et al. 2017). All metabolic
enzymes belong to the group of hydrolases, lyases, transferases, oxidoreductases,
ligases and isomerases (Abatenh et al. 2017). Enzymes are biocatalysts that help in
the facilitation of transformation of reactants into products by the provision of
positive conditions to lessen the activation energy during reaction found universally
in all living organisms (Ahuja et al. 2004; Karigar and Rao 2011). Enzymes are not
expensive and catalysts that are friendly to nature with the capability of
bioremediating the many harmful compounds that are not friendly to our environment as per studied present scenario of societal ecological standards (Rao et al. 2010;
Karigar and Rao 2011).
Structurally an enzyme is a protein that consists of one polypeptide moiety, and
the part of these biocatalysts that actively takes part in the catalytic processes is
known as active sites. These biocatalysts have one or more groups that are necessary
for their catalytic activity, associated with the active sites, either by covalent or by
other bonds; this protein part in such enzymes is called apoenzyme. On the other
hand, the non-protein part is generally called as the prosthetic group. Both apoenzyme and prosthetic groups combine to form holoenzyme (Karigar and Rao 2011).
The action of enzymes may be intracellular, i.e. on the inner side of the cells from
where they are originated or act extracellularly, i.e. in the absence of cells of their
origination. If the enzyme is presently free, i.e. insoluble form, this type of catalysis
is known as homogenous, or immobilized; on the other hand, if the enzyme is linked
through a solid matrix, then catalysis is called as heterogeneous. The main producers
of these catalysts are generally white-rot fungi, bacteria, and microbe-plant
associations (Rao et al. 2010). The extracellular enzymes produced by fungi especially filamentous fungi is paramount because it is primarily utilized bioremediating
or neutralizing toxic contaminants, for instance, polycyclic aromatic hydrocarbons
(PAHs), which is a primary toxic pollutant that poses a potential risk to human health
(Bonugli-Santos et al. 2010).
Enzyme-based degradation process usually occurs at a faster rate than abiotic
oxidation reactions as well as organic chemical pollutants that moves into the
metabolic pathway carried out by microbes present in the soil. The reason behind
this enzyme-based reaction is the free energy potential which is being used by the
microbes for degradation processes (Jonsson and Haller 2014). Table 15.1 shows
various enzymes produced by various microorganisms and the substrate they act
upon for degradation. The development of enzymes for the process of remediation
usually done in three steps mentioned below:
(i) Isolation and identification of template enzyme from the natural resources.
(ii) Isolation of the genes that encode for a particular enzyme.
(iii) Improvement of enzymatic efficiency by improving enzyme properties in the
laboratory (Sutherland et al. 2004).
15 The Role of Microorganisms in Remediation of Environmental Contaminants
437