the hydrolysis products from starch for neutralizing alkaline waste waters from the
pulp and paper and textile industries, which are not only alkaline but also contain
starch. Apart from neutralization of the pH of alkaline waste waters, these enzymes
break down the polysaccharides present in the industrial effluents, thereby reducing
the biochemical oxygen demand (BOD), chemical oxygen demand (COD) and
suspended solids.
An area that is gaining popularity in waste water treatment is nanotechnology,
whereby nanoparticles are used for degradation of contaminants to harmless
products like water and CO 2 [110]. Bioremediation of waste water can be achieved
by using a combination of enzyme technology and nanotechnology known as
SEN, that is, single-enzyme nanoparticle [111]. A SEN is an enzyme covered by a
protective thick cage that is a few nanometres. Typically, either cell-free crude
extracts or purified enzymes are used for SEN formulation. Nanotechnology
has been successfully applied in immobilization and stabilization of amylolytic
enzymes including α-amylases, β-amylases, glucoamylases and pullulanases [112].
Immobilization improves enzyme performance and helps to minimize steric
hindrances during binding of substrate to the active site of the enzyme. It also results
in enzymes with very high resistance to inactivation, high activity and stability,
thus enabling their repeated and continuous use in applications in other areas
than waste water treatment, such as food, fuel, textile, paper and pulp, detergent,
environmental, medical and analytical fields [112]. A Bacillus alcalophilus alkalineactive α-amylase was immobilized onto nanosized supermagnetic iron oxide magnetic nanoparticles (MNPs) [113]. The immobilized enzyme exhibited significantly
higher specific activity, stability and reusability as compared to the free enzyme.
Such enzyme formulations would be suitable for application where alkaline conditions prevail, such as in alkaline waste water treatment, detergent, textile, paper and
pulp industries.
4.8 Leather Industry
Conventional leather processing or beam-house operations involve the use of
chemicals such as lime and sodium sulphide for the dehairing of animal skins at
alkaline conditions. The liming-reliming processes contribute 60–70% of the total
pollution load in leather processing [114]. There have been eco-friendly initiatives to
address this through the use of enzymes to replace the toxic chemicals for these
processes. Proteases and lipases have been applied for the unhairing and degreasing/
defleshing of the animal skins and hides with several advantages. These include
preservation of skin colour and significant reduction of BOD and COD values of
effluents [115, 116]. Furthermore, enzymatically processed skins produced crust
leather that exhibited similar physical and tactile properties as compared to conventional crust leather produced by chemicals. In a recent study, an α-amylase was used
for fibre splitting of goatskins, with the aim of reducing pollution from beam-house
processes [114]. The use of the enzyme resulted in a lower pollution load (COD,
Starch-Modifying Enzymes
237
pulp and paper and textile industries, which are not only alkaline but also contain
starch. Apart from neutralization of the pH of alkaline waste waters, these enzymes
break down the polysaccharides present in the industrial effluents, thereby reducing
the biochemical oxygen demand (BOD), chemical oxygen demand (COD) and
suspended solids.
An area that is gaining popularity in waste water treatment is nanotechnology,
whereby nanoparticles are used for degradation of contaminants to harmless
products like water and CO 2 [110]. Bioremediation of waste water can be achieved
by using a combination of enzyme technology and nanotechnology known as
SEN, that is, single-enzyme nanoparticle [111]. A SEN is an enzyme covered by a
protective thick cage that is a few nanometres. Typically, either cell-free crude
extracts or purified enzymes are used for SEN formulation. Nanotechnology
has been successfully applied in immobilization and stabilization of amylolytic
enzymes including α-amylases, β-amylases, glucoamylases and pullulanases [112].
Immobilization improves enzyme performance and helps to minimize steric
hindrances during binding of substrate to the active site of the enzyme. It also results
in enzymes with very high resistance to inactivation, high activity and stability,
thus enabling their repeated and continuous use in applications in other areas
than waste water treatment, such as food, fuel, textile, paper and pulp, detergent,
environmental, medical and analytical fields [112]. A Bacillus alcalophilus alkalineactive α-amylase was immobilized onto nanosized supermagnetic iron oxide magnetic nanoparticles (MNPs) [113]. The immobilized enzyme exhibited significantly
higher specific activity, stability and reusability as compared to the free enzyme.
Such enzyme formulations would be suitable for application where alkaline conditions prevail, such as in alkaline waste water treatment, detergent, textile, paper and
pulp industries.
4.8 Leather Industry
Conventional leather processing or beam-house operations involve the use of
chemicals such as lime and sodium sulphide for the dehairing of animal skins at
alkaline conditions. The liming-reliming processes contribute 60–70% of the total
pollution load in leather processing [114]. There have been eco-friendly initiatives to
address this through the use of enzymes to replace the toxic chemicals for these
processes. Proteases and lipases have been applied for the unhairing and degreasing/
defleshing of the animal skins and hides with several advantages. These include
preservation of skin colour and significant reduction of BOD and COD values of
effluents [115, 116]. Furthermore, enzymatically processed skins produced crust
leather that exhibited similar physical and tactile properties as compared to conventional crust leather produced by chemicals. In a recent study, an α-amylase was used
for fibre splitting of goatskins, with the aim of reducing pollution from beam-house
processes [114]. The use of the enzyme resulted in a lower pollution load (COD,
Starch-Modifying Enzymes
237