22.4 Commonly Functionalized Biomaterials and Their Role in Remediation

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been tested for their applicability for PAH remediation. Oxidizer-catalyzed reaction

leads to the covalent attachment of PAH to protein biomolecules. Iron-containing

hemoglobin protein having four protein chains (two α and two β) encapsulated

with silica nanoparticles have been tested for PAH removal from wastewater. This

protein conjugate was tested ex situ and recorded a hydrocarbon removal efficiency

of 82% from PAH-polluted water at pH 5 [31]. Citric acid-conjugated magnetic

nanoparticles react with collagen to form superparamagnetic iron oxide-based

nanoparticles with excellent oil-absorbing capability. These superparamagnetic

oxides functionalized nanoparticles are functional and stable even at 87 ^∘C and can

absorb oil twice its weight [32]. Zero-valent iron conjugated with soy protein has

been patented for its promising application in water and soil remediation [33]. With

the advancement of genetic engineering technologies, we can now exploit various

recombinant proteins for the bioremediation of multiple pollutants. One such

example of the recombinant fusion protein is Pb-specific metalloprotein “PbrD”

which is cross-linked to nanoparticles like calcium alginate for the removal of

Pb(II) from water. The uptake rate of Pb by Pb-specific metalloprotein cross-linked

calcium alginate was found to be 8.82 mg/g at 100 mg/l concentration in the initial

screening. This promising result shows its applicability in recovering Pb from acid

mine drainage and industrial effluents [34].

22.4.5

Enzymes

Enzyme-immobilized nanoparticles have the benefit of prolonged operational flex-

ibility, fast recovery, ease of reuse, lower associated expenses, and high efficiency.

These advantages are driving the attention of researchers for developing techniques

for bioremediation of environmental pollution. Enzyme characteristics and dynam-

ics are susceptible to pH, temperature, nature of medium/environment of action,

type of attachment with nanoparticles or matrix, and distance of core nanoparticle

with the enzyme. These parameters critically drive the catalytic efficiency of the

functionalized enzyme. Conjugating enzyme on the outer surface of the nanoparti-

cle, where the nanoparticle is at the core, provides the particle enhancement/dual

functionality and generally referred to as enzyme-nanoparticle corona. Enzyme-

conjugated nanoparticles prevent agglomeration and provide better bioavailability.

The main enzymes used for bioremediation include peroxidase, oxygenase, and

laccase. These enzymes are the member of the oxidoreductase family and have an

enzyme commission (EC) number 1. They catalyze a reaction by transferring an

electron from donor to acceptor, and the contaminants are oxidized to a less harmful

form. Monooxygenase enzymes are used for remediation of various aromatic and

aliphatic compounds, and they catalyze many by dehalogenation, denitrification,

ammonification, desulfurization, and hydroxylation reaction. Various examples of

enzyme-based nanoparticles for environmental applications are discussed below.

Laccase is a highly potent catalytic agent for the bioremediation of contam-

inants from the textile and petrochemical industries. Organic pollutants like

chlorophenol, dyes, and various paper wastes can be remediated using laccase.

Trametes versicolor-derived laccase conjugated into chitosan-encapsulated magnetic