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5 Bioremediation of Heavy Metals

5.6

Conclusion

Environmental heavy metal pollution is the contamination of soil, water and air

with heavy metals that now became one of the most serious global environmental

problems. As metals are non-biodegradable, can accumulate in living organisms

via the ecological food web and some of these metals are extremely toxic in trace

concentrations and can cause devastating health problems worldwide. The persis-

tent nature of heavy metals makes the environmental removal of the heavy metal

a realistic problem especially in case of the industries using heavy metals in their

productions. The devastating scenario of environmental heavy metal pollution is

more intense for the population of developing countries, relying mostly on growing

necessity of industries, making the contamination of environment with heavy

metals a great concern due to the fact that it consequently affects the health of

animals and plants [1].

Several bioaccumulating agents have been reported earlier; for instance, fungi and

bacteria could serve as potential candidate of bioremediation by bioaccumulation

[1, 5, 6]. Penicillium and Aspergillus were reported to be the efficient bioaccumula-

tors, whereas bacteria such as Bacillus spp., Pseudomonas sp., Enterobacter spp., and

Aeromonas spp. have an ability to decontaminate heavy metals [38]. Similarly, Peni-

cillium rubens was found the second best Cd bioaccumulator and Aspergillus fumi-

gatus showed remediation potential for Cd and Cr removal. Metarhizium anisopliae,

Saccharomyces cerevisiae, Fusarium oxysporum and two species of Penicillium have

also been reported for their bioremediation potential against Cd and other heavy

metals [39]. Studies also shown that Aspergillus sp., Penicillium sp., and Yarrowta sp.

can remove both soluble and insoluble heavy metal species from solution [40]. The

biosorption of Cr(VI) and Fe(III) has been shown in Streptococcus equisimilis and

S. cerevisiae. Significant Cr(VI) removal was observed using growing cells in batch

and continuous modes of operations and using non-living biomass in a batch biore-

actor. They conducted the study to evaluate the potential of the resting cells of the

Fusarium solani for Cr(VI) removal from aqueous solution with an aim to develop a

suitable operational strategy for the treatment of Cr(VI)-contaminated wastewaters.

According to Jiang et al. [41], the microbial isolates Chryseobacterium indoltheticum,

Pseudomonas helmanticensis, Bacillus mycoides, Bacillus almalaya and Acinetobac-

ter showed high tolerance to Cd, Pb, Cr and Zn. Thus, the use of microbial biomass

may therefore be considered as remedy for the removal of toxic substances from the

environment. Not only being cost-effective, the indigenous microorganisms isolated

also detoxify the contaminated site itself, to exercise their natural power and rem-

edy the situation. Industrialization is the best known cause for heavy metal pollution

of the soil and bioleaching is the most efficient, cost-effective and environmentally

friendly method. Fungi could be the most suitable bioaccumulating agents for the

removal of cadmium and chromium from contaminated soil. Considering the threat

of these heavy metals to human health, the future challenge is to remove toxic metal-

loid from our habitable ecological niche. The myriad arrays of resistant adaptations

in contemporary life forms are the evolutionary tools for the sustainable environ-

mental bioremediation [5, 6]. Furthermore, deeper investigations for linking the