Zhu et al. (2007) for laccase immobilization. Laccase sorbed onto carbon-based
mesoporous magnetic nanocomposite was applied by Liu et al. (2012) for successful removal of phenol and p-chlorophenol.
The interest in the synthesis of various hybrid nanocomposites is rapidly increasing and several specific techniques have been published in recent years. Song et al.
(2017) reported a novel strategy for enzyme immobilization based on DNA strand
displacement on modified magnetic nanoparticles using alkaline phosphatase and
horseradish peroxidase. Woo et al. (2015) introduced a nanosized magnetite impregnated mesocellular foam composite with Cu ligand as an enzyme carrier. Cao et al.
(2016) prepared and successfully used magnetic cellulose nanocrystals as an enzyme
support for Pseudomonas cepacia lipase immobilization via precipitation followed
by a cross-linking process.
16.7 Application of Nanobiocatalyst for Remediation
Nanobiocatalysts may be used for remediation of contaminated wastewater or soil.
Many studies have been published over the past 5 years (Table 16.1). It is obvious
that field application of nanobiocatalysts is still in its infancy. Most of the work is
focused on synthesis and evaluation of new nanocomposites. Remediation efficiency
of the nanobiocatalysts was tested with various pollutants including phenolic compounds, synthetic dyes, pharmaceuticals, and PAHs. The treatment was mostly
performed in artificially spiked standard solutions in batch systems, which often
does not reflect real conditions. Removal of the pollutants by biocatalyst-containing
nanocomposites is actually the result of many concurrent processes, which include
mainly enzymatic degradation, physical adsorption, and sometimes polymerization.
Removal efficiency is dependent especially on the pH, the concentration of the
pollutant, and the presence of redox mediators, as well as matrix effects. The
biocatalyst nanocomposites usually showed high enzyme loading and enhanced
catalytic activity and stability compared to the corresponding free enzymes. The
pollutant removal efficiency was mostly >80%; however, as it was mentioned above,
most of the research was performed in buffered conditions.
Several research groups tested remediation processes using nanobiocatalysts in
continuous flow mode. To retain the immobilized enzymes and separate them from
the treated water, membrane hybrid reactors are commonly operated. A laboratory
scale perfusion basket reactor was used by Kumar et al. (2014) in order to study the
continuous decolorization of dyes by a laccase enzyme from Trametes versicolor
immobilized onto amino-functionalized magnetic nanoparticles. The efficient decolorization (>90%) of Remazol brilliant blue R and slight decrease in nanoparticle
activity were measured over a 10-hour period of continuous operation. Zhang et al.
(2015) synthesized a novel biocatalyst by coating polyethylenimine onto the native
laccase followed by cross-linking with glutaraldehyde. The carrier-free nanogels
exhibited enhanced stability, high catalytic activity, and favorable properties for
membrane separation. The cyclic decolorization of Acid orange 7 demonstrated that
16 Enzyme-Based Nanomaterials in Bioremediation
355
mesoporous magnetic nanocomposite was applied by Liu et al. (2012) for successful removal of phenol and p-chlorophenol.
The interest in the synthesis of various hybrid nanocomposites is rapidly increasing and several specific techniques have been published in recent years. Song et al.
(2017) reported a novel strategy for enzyme immobilization based on DNA strand
displacement on modified magnetic nanoparticles using alkaline phosphatase and
horseradish peroxidase. Woo et al. (2015) introduced a nanosized magnetite impregnated mesocellular foam composite with Cu ligand as an enzyme carrier. Cao et al.
(2016) prepared and successfully used magnetic cellulose nanocrystals as an enzyme
support for Pseudomonas cepacia lipase immobilization via precipitation followed
by a cross-linking process.
16.7 Application of Nanobiocatalyst for Remediation
Nanobiocatalysts may be used for remediation of contaminated wastewater or soil.
Many studies have been published over the past 5 years (Table 16.1). It is obvious
that field application of nanobiocatalysts is still in its infancy. Most of the work is
focused on synthesis and evaluation of new nanocomposites. Remediation efficiency
of the nanobiocatalysts was tested with various pollutants including phenolic compounds, synthetic dyes, pharmaceuticals, and PAHs. The treatment was mostly
performed in artificially spiked standard solutions in batch systems, which often
does not reflect real conditions. Removal of the pollutants by biocatalyst-containing
nanocomposites is actually the result of many concurrent processes, which include
mainly enzymatic degradation, physical adsorption, and sometimes polymerization.
Removal efficiency is dependent especially on the pH, the concentration of the
pollutant, and the presence of redox mediators, as well as matrix effects. The
biocatalyst nanocomposites usually showed high enzyme loading and enhanced
catalytic activity and stability compared to the corresponding free enzymes. The
pollutant removal efficiency was mostly >80%; however, as it was mentioned above,
most of the research was performed in buffered conditions.
Several research groups tested remediation processes using nanobiocatalysts in
continuous flow mode. To retain the immobilized enzymes and separate them from
the treated water, membrane hybrid reactors are commonly operated. A laboratory
scale perfusion basket reactor was used by Kumar et al. (2014) in order to study the
continuous decolorization of dyes by a laccase enzyme from Trametes versicolor
immobilized onto amino-functionalized magnetic nanoparticles. The efficient decolorization (>90%) of Remazol brilliant blue R and slight decrease in nanoparticle
activity were measured over a 10-hour period of continuous operation. Zhang et al.
(2015) synthesized a novel biocatalyst by coating polyethylenimine onto the native
laccase followed by cross-linking with glutaraldehyde. The carrier-free nanogels
exhibited enhanced stability, high catalytic activity, and favorable properties for
membrane separation. The cyclic decolorization of Acid orange 7 demonstrated that
16 Enzyme-Based Nanomaterials in Bioremediation
355