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Bioremediation for Sustainable Environmental Cleanup

and various microorganisms, in our laboratory. Various biohybrids in microstructures morphologies

using silica nanoparticles and biomolecules through the process of evaporation induced self-

assembly (Mishra et al. 2014, Mukundan et al. 2020). In one of the studies, microstructures of silica

NPs and Streptococcus lactis (S. lactis) cells were prepared, utilized for removal of uranium and

adsorbed uranium was recovered using ultra sonication (Mishra et al. 2014, Lahiri et al. 2021). It is

possible to get different morphologies of microstructures by tuning the physico-chemical parameters

of evaporation induced by self-assembly process. Synthesized products were characterized and it

has shown that morphology depended on removal of uranium. Among spherical and doughnut-

shaped microstructures, doughnut-shaped microstructures have shown higher uranium uptake.

The adsorbed uranium was also recovered using ultrasonic treatment however, after treatment the

binding capacity of microstructures were reduced during reusability studies. The plausible cause

for reduced sorption may be changes in morphology of microstructures and decrease in number of

adsorption sites after acid and ultrasonic treatment. On a similar line of studies, a bio-hybrid of silica

NPs and S. cerevisiae cells were developed and employed for mercury (Hg²⁺) removal. It has shown

98% mercury sorption with maximum sorption 185.19 mgg^–1 (Shukla et al. 2020). It was observed

that these microstructures could be used as a sorbent for remediation of mercury. In summary, spray

drying has emerged as a simple, efficient and cost-effective process for synthesizing functionalized

silica-based sorbents using microbial cells. Prepared biohybrids are of higher length scale thus they

could be easily separated once the sorption process is completed. Physico-chemical characterization

has also shown that microbial cell surfaces are available for binding to metal ions in the biohybrids.

These characteristics make synthesized biohybrids a suitable and efficient sorbent. S. lactis cells

express β-galactosidase activity and hydrolyzes lactose, thus the enzyme activity was studied in the

microstructures comprising S. lactis cells and silica NPs (Mukundan et al. 2020). The result was

encouraging as the cells entrapped in microstructures have shown higher enzymatic activity than

the free cells.

The environment’s growing concentration of heavy metal ions creates a major hazard to living

beings. For the quick and highly effective removal of diverse contaminants, adsorption methods

based on a range of micro/nanomaterials and micro/nanomanipulation are being used. Magnetic

Fe3O4 nanoparticles were grown in-situ on hydrothermally treated fungus spores to create a particular

type of biohybrid adsorbent (Zhang et al. 2018). Due to their porous structure and high adsorbing

components, such organic/inorganic Porous Spore@Fe3O4 Biohybrid Adsorbents (PSFBAs) could

efficiently adsorb and remove heavy metal ions. In comparison to their non-motile counterparts,

magnetic PSFBAs in controllably collective motion exhibited improved adsorption capacity and

quicker removal times for a number of heavy metal ions. It was shown how the collective magnetic

actuation of PSFBAs crowded into a small fluidic channel worked. In comparison to untreated and

static equivalents, using these adsorbents and a magnetically propelled swarming micro robotic

method, lead ions in polluted water were swiftly removed from 5 ppm down to 0.9 ppm. Four

successive cycles show that such magnetically propelled PSFBAs may be reused following simple

separation and post-treatment (Zhang et al. 2018). A possible approach for the decontamination of

toxins in environmental restoration would be the combination of biological entities with swarming

microrobotic systems.

15.8 Conclusion and Future Prospective

In this chapter, biohybrids, their different components and the importance of the components and

methods of synthesizing biohybrids were described. The association of biomolecules with suitable

supports enhances the applicability of biohybrids. Biomolecules have enzymatic activity and other

biological processes thus biohybrids could be used as smart sensing materials against various

analytes. On the other hand, the support acts as a protective covering and protects the biomolecules

from the surrounding harsh environment.