6.6 Bioremediation Process Using Biological Mediators

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microorganisms. Biodegradation involves various steps depending on the contam-

inant and each step was initiated by specific enzymes which present in bacterial

cells. Biodegradation of contaminants by either internal or external enzymes will

break at any phase if a suitable enzyme is absent. Lack of specific enzymes is one

of the reasons for the accumulation of byproducts of contaminants. Hence, specific

enzyme-bearing microorganisms are introduced into the soil and water to improve

the activity of biodegradation. Indigenous bacterial cultures are capable of metab-

olizing contaminants. Biodegradation can be through either aerobic or anaerobic

mechanisms [34]. Several pesticide-degrading genes were identified on the plasmids

of soil bacteria, which are known as catabolic plasmids. They are found in the species

of Flavobacterium, Pseudomonas, Rhodococcus, and Alcaligenes which can degrade

pesticide contaminants.

6.6.2

Fungal Remediation

Fungi produce a variety of extracellular enzymes and fungal species possess high

capacity to degrade pesticides. Branching and filamentous fungal growth will per-

mit for effective colonization and examination of contaminated soil. White-rot fungi

are filament-like creatures and propose advantages over bacteria as they are better

oxidizers. They are strong organisms and are mostly extra tolerant to high concen-

trations of polluting chemicals than bacteria. Additional fungi that can be used in

bioremediation are zygomycetes, e.g. mycorrhizal and mucoraceous fungi. Anaero-

bic aquatic fungi can also be used for bioremediation [26].

6.6.3

Phytoremediation

It is the method which uses the living plants and their allied microorganisms

for in situ elimination and degradation of contaminants present in soil, ground

water, and surface water. Plants can accumulate and metabolize organic pollutants

(phytodegradation) or stimulate rhizospheric microorganisms (phytostimulation).

Phytoremediation is a less cost-consuming, eco-friendly, and easier for the remedi-

ation of adulterated soil and water using plants. Plants used will have an exclusive

and careful uptake capability of roots, with the translocation, bioaccumulation,

and degradation of contaminant. Plant-dependent soil remediation systems are

biological, solar-driven, and capable of self-extending uptake network systems

which enhance the underground ecosystem for productive use. Plant possesses a

favorable microenvironment in the root zone that leads to contaminant degradation.

In the soil, plant-associated bacteria are endophytic (nonpathogenic) and rhizo-

spheric. Endophytic bacteria effortlessly occur in the interior tissues of plants which

promote plant growth and degrade soil contaminants. Rhizospheric bacteria have

a capacity to degrade various agrochemicals due to enhanced microbial activity.

Advancements in recombinant DNA technology have created transgenic plants that

exhibit better-quality tolerance and catabolic activity against contaminants present

in the soil [35].