making a major impact on analytical and preparative separations. However,
large-scale processes, while enjoying the same mass transfer advantages as their
small-scale counterparts, suffer from poor heat rejection. Hence the prospects
for electrophoretic extraction of cells/macromolecules and electrokinetic
demixing of biphasic systems to some extent depend also on the economic success of their parent processes.
One of the critical factors in the industrial purification of enzymes and
proteins using ATPE is the selection of the appropriate system. Most of the
large-scale purifications reported in the literature use either PEG/DX or
PEG/salt systems. These systems have a number of desirable characteristics,
such as suitable physical properties, non-toxicity, and biodegradability, and are
approved by the regulatory authorities. However, the high cost of fractionated
DX (approximately $500/kg) and the high salt concentrations (of the PEG/salt
systems) have necessitated a search for suitable alternatives. Technical feasibility as well as the cost effectiveness of crude DX ($15/kg) [151], hydroxy propyl
starch (HPS) ($20/kg)[152], along with PEG was successfully demonstrated for
large-scale enzyme purification.
At this juncture, the PEG/maltodextrin (MDX) system [153, 154] appears to
be the most cost-effective ATPS (cost of MDX is $1/kg) though the large-scale
operations using real systems have yet to be carried out using this system. The
productivity of the purification process increases considerably, especially for
intracellular enzymes, which in turn improves the economics of the process,
when ATPE is employed instead of conventional methods as indicated by
Kroner et al. [151].
The cost of waste treatment is another important factor as rightly indicated
by Kula [155]. Phase-forming polymers like PEG, DX, and MDX are biodegradable and non-toxic; however, salt (sulfates and phosphates) disposal is
problematic. Hence phase-forming components have to be recycled a few times
before discarding, thus improving the economics [156].
5
Other Applications
Magnetic extraction being a potential method needs thorough exploration for
its application in other areas, including food processing. Some possible
applications are cited here, which will prompt researchers to look for similar
applications elsewhere.
Purification of water in hydrocyclones in a magnetic field is reported [157]
to meet the high water recirculation demand (640–800 m 3 /day) for hydrothermal processing of wheat in a 320 t/day capacity mill.
Separation of an ethanol-water system was achieved by magnetic field
where ethanol yield was 2% higher over the conventional method. Magnetic
field was found to increase aluminum sulfate dissolution coefficient by
10–20%, depending on the quality of the treatment. Theoretical elucidation of
the effect of the magnetic field on aqueous solutions is also given [158].
High gradient magnetic separation (HGMS) was observed to be a potential
treatment for food processing wastewater. HGMS treatment of composite waste
182
K.S.M.S. Raghavarao et al.
large-scale processes, while enjoying the same mass transfer advantages as their
small-scale counterparts, suffer from poor heat rejection. Hence the prospects
for electrophoretic extraction of cells/macromolecules and electrokinetic
demixing of biphasic systems to some extent depend also on the economic success of their parent processes.
One of the critical factors in the industrial purification of enzymes and
proteins using ATPE is the selection of the appropriate system. Most of the
large-scale purifications reported in the literature use either PEG/DX or
PEG/salt systems. These systems have a number of desirable characteristics,
such as suitable physical properties, non-toxicity, and biodegradability, and are
approved by the regulatory authorities. However, the high cost of fractionated
DX (approximately $500/kg) and the high salt concentrations (of the PEG/salt
systems) have necessitated a search for suitable alternatives. Technical feasibility as well as the cost effectiveness of crude DX ($15/kg) [151], hydroxy propyl
starch (HPS) ($20/kg)[152], along with PEG was successfully demonstrated for
large-scale enzyme purification.
At this juncture, the PEG/maltodextrin (MDX) system [153, 154] appears to
be the most cost-effective ATPS (cost of MDX is $1/kg) though the large-scale
operations using real systems have yet to be carried out using this system. The
productivity of the purification process increases considerably, especially for
intracellular enzymes, which in turn improves the economics of the process,
when ATPE is employed instead of conventional methods as indicated by
Kroner et al. [151].
The cost of waste treatment is another important factor as rightly indicated
by Kula [155]. Phase-forming polymers like PEG, DX, and MDX are biodegradable and non-toxic; however, salt (sulfates and phosphates) disposal is
problematic. Hence phase-forming components have to be recycled a few times
before discarding, thus improving the economics [156].
5
Other Applications
Magnetic extraction being a potential method needs thorough exploration for
its application in other areas, including food processing. Some possible
applications are cited here, which will prompt researchers to look for similar
applications elsewhere.
Purification of water in hydrocyclones in a magnetic field is reported [157]
to meet the high water recirculation demand (640–800 m 3 /day) for hydrothermal processing of wheat in a 320 t/day capacity mill.
Separation of an ethanol-water system was achieved by magnetic field
where ethanol yield was 2% higher over the conventional method. Magnetic
field was found to increase aluminum sulfate dissolution coefficient by
10–20%, depending on the quality of the treatment. Theoretical elucidation of
the effect of the magnetic field on aqueous solutions is also given [158].
High gradient magnetic separation (HGMS) was observed to be a potential
treatment for food processing wastewater. HGMS treatment of composite waste
182
K.S.M.S. Raghavarao et al.