5.5 Bioremediation – The Emerging Sustainable Strategy

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tabacum, and Zea mays, have been reported to effectively remove heavy metals

from contaminated soil through phytoextraction. Phytoextraction of Cd, Pb, Cu,

and Zn has been observed in Trifolium alexandrinum earlier [32] due to its fast

growth, resistance to pollution, high biomass, and other favorable parameters. It has

also been speculated that phytoextraction of heavy metals will be a commercially

viable technology for phytoremediation and phytomining of heavy metals in future.

The combinatorial approach involving genetic engineering, microbe-assisted

approaches, is essential for highly effective and sustainable phytoremediation of

environmental heavy metal.

5.5.3

Algae-Assisted Bioremediation (Phycoremediation)

Algae also perform well in the field of bioremediation. The term “phycoremedia-

tion” is used to denote the remediation that includes either removal or degradation

and assimilation, using various types of algae and cyanobacteria. Similar to bacteria,

algae have various chemical moieties on their surface such as hydroxyl, carboxyl,

phosphate, and amide, which act as metal-binding sites. In a study, different species

of brown algae were examined for their metal uptake activity. Among them, Padina

sp. and Cystoseira sp. were reported to have effective metal uptake capabilities [35].

5.5.4

Fungi-Assisted Bioremediation (Mycoremediation)

It has been shown previously that bioleaching is a biological process in which

microorganisms (fungi, algae, and bacteria) uptake heavy metals from the environ-

ment. It has been reported that fungi are considered the most suitable candidates

for bioremediation due to their high tolerance to heavy metals with higher

surface-to-volume ratio. The main advantage to use an indigenous fungal strain

is that they are adapted not only to the presence of contaminants but also to the

environmental condition of the site. Thus, there is a need to develop new strategies

to utilize indigenous fungal strains for heavy metal removal from contaminated soil.

Fungi are also being utilized as a contrivance for the remediation of heavy

metal–contaminated areas because of their ability to accumulate toxic metals.

Coprinopsis atramentaria is studied for its bioaccumulation capacity of Cd and Pb.

Hence, it has been recognized as a potential accumulator of heavy metal ions and a

very important tool for mycoremediation.

Fungi have the ability to uptake both essential and non-essential heavy metals

[36]. Fungal survival in heavy metal–contaminated environments mainly depends

on intrinsic structural and biochemical properties, genetical and/or physiolog-

ical adaptation, morphological changes, environmental modification of heavy

metal, its toxicity, and availability. Biological mechanisms associated with fungal

existence include extracellular precipitation, crystallization, transformation, and

complexation of metal species by using mechanisms such as reduction, oxidation,

dealkylation, methylation, biosorption to cell walls, extracellular polysaccha-

ride and pigments, impermeability or decreased transport, efflux, intracellular

compartmentation and sequestration [37].