potential (Viswanath et al. 2014). They are produced intra- and extracellularly and
can be relatively simply isolated and purified from different organisms that include
mainly bacteria (Muthukumarasamy et al. 2015) and white-rot fungi (Shraddha
et al. 2011). Laccases catalyze the oxidation of a wide range of phenolic and
aromatic compounds. They can decolorize industrial textile effluents (Zucca et al.
2015) and initiate depolymerization reactions (Dashtban et al. 2010). It has been
reported that laccases are involved in the degradation of highly recalcitrant environmental pollutants such as pharmaceuticals (Yang et al. 2017) and polycyclic
aromatic hydrocarbons (Kadri et al. 2017). Peroxidases are oxidoreductases that
oxidize organic compounds using hydrogen peroxide. Peroxidases are produced by
a variety of different organisms and the most investigated types include lignin
peroxidase, manganese-dependent peroxidase, and versatile peroxidase. Peroxidases have the potential for bioremediation of wastewater and soil contaminated
with phenols, cresols, textile dyes, endocrine disruptive chemicals as well as several
pesticides and herbicides (Bansal and Kanwar 2013).
Hydrolytic enzymes participate in the degradation of pollutants by breaking
major chemical bonds. Lipases hydrolyze triacylglycerols into glycerol and free
fatty acids and are used for effective removal of oil spills and reduction of hydrocarbons (Cammarota and Freire 2006). Further hydrolytic enzymes such as amylases, celluloses, and proteases are involved in the degradation of macromolecules in
the activated sludge process (Guo and Xu 2011).
Further details on the role of microbial enzymes in the biodegradation of pollutants have been thoroughly reviewed elsewhere (Karigar and Rao 2011; Eibes et al.
2015; Kües 2015).
16.3 Why Immobilization?
Enzymatic degradation represents an eco-friendly remediation technique. However,
it faces major hurdles which still hinder its sustainable and low cost applications.
Soluble enzymes often exhibit a limited stability in contaminated environmental
matrices. The immobilization of enzymes on solid supports in order to enhance the
stability and improve the activity has been demostrated.
The immobilization process usually increases the enzyme stability against high
temperature, pH variations, organic solvents and detergents during both storage and
process operation. Enzyme activity is maintained or even significantly enhanced
upon immobilization, which could be caused by conformational changes (Secundo
2013). Furthermore, the immobilized enzymes can be retained, separated, and
applied in bioreactors operated in a continuous mode. Immobilization may reduce
operational costs not only by improving the catalyst properties but also by enabling
efficient recycling and controlling the process. Immobilization increases the area of
application and facilitates large-scale implementation of the enzymatic processes
(Rao et al. 2014).
16 Enzyme-Based Nanomaterials in Bioremediation
347
can be relatively simply isolated and purified from different organisms that include
mainly bacteria (Muthukumarasamy et al. 2015) and white-rot fungi (Shraddha
et al. 2011). Laccases catalyze the oxidation of a wide range of phenolic and
aromatic compounds. They can decolorize industrial textile effluents (Zucca et al.
2015) and initiate depolymerization reactions (Dashtban et al. 2010). It has been
reported that laccases are involved in the degradation of highly recalcitrant environmental pollutants such as pharmaceuticals (Yang et al. 2017) and polycyclic
aromatic hydrocarbons (Kadri et al. 2017). Peroxidases are oxidoreductases that
oxidize organic compounds using hydrogen peroxide. Peroxidases are produced by
a variety of different organisms and the most investigated types include lignin
peroxidase, manganese-dependent peroxidase, and versatile peroxidase. Peroxidases have the potential for bioremediation of wastewater and soil contaminated
with phenols, cresols, textile dyes, endocrine disruptive chemicals as well as several
pesticides and herbicides (Bansal and Kanwar 2013).
Hydrolytic enzymes participate in the degradation of pollutants by breaking
major chemical bonds. Lipases hydrolyze triacylglycerols into glycerol and free
fatty acids and are used for effective removal of oil spills and reduction of hydrocarbons (Cammarota and Freire 2006). Further hydrolytic enzymes such as amylases, celluloses, and proteases are involved in the degradation of macromolecules in
the activated sludge process (Guo and Xu 2011).
Further details on the role of microbial enzymes in the biodegradation of pollutants have been thoroughly reviewed elsewhere (Karigar and Rao 2011; Eibes et al.
2015; Kües 2015).
16.3 Why Immobilization?
Enzymatic degradation represents an eco-friendly remediation technique. However,
it faces major hurdles which still hinder its sustainable and low cost applications.
Soluble enzymes often exhibit a limited stability in contaminated environmental
matrices. The immobilization of enzymes on solid supports in order to enhance the
stability and improve the activity has been demostrated.
The immobilization process usually increases the enzyme stability against high
temperature, pH variations, organic solvents and detergents during both storage and
process operation. Enzyme activity is maintained or even significantly enhanced
upon immobilization, which could be caused by conformational changes (Secundo
2013). Furthermore, the immobilized enzymes can be retained, separated, and
applied in bioreactors operated in a continuous mode. Immobilization may reduce
operational costs not only by improving the catalyst properties but also by enabling
efficient recycling and controlling the process. Immobilization increases the area of
application and facilitates large-scale implementation of the enzymatic processes
(Rao et al. 2014).
16 Enzyme-Based Nanomaterials in Bioremediation
347