In ion exchange chromatography,
substances can be separated according
to their charge. It is based on the formation
of heteropolar bonds between the
matrix and the mobile phase, whereby
the desired charged protein binds. The
elution can be done by means of gradients.
As soon as the charge binding between
eluent and protein is higher than
between matrix and protein, the protein
migrates into the solution. By detecting
the flow at 280 nm, any passing protein
can be detected as a peak. In lactoferrin
recovery, LF is obtained by ion exchange
chromatography.
What is Radial Flow?
The radial flow stands for a continuous
flow and high flow rate through
the entire adsorber (24/7), a low differential
pressure at a high flow rate,
the processing of large feed volumes
and a good scalability by increasing the
separation distance of the corresponding
radial flow column.
More advantages of RFC are the following:
• Bidirectional flow
• Ability to sterilize and autoclave the
column
• Availability of different screen sizes
• Small footprint
• Low dead space volume
• Minimum ΔP
• Robust design
• Specific packing station for easy packing
and unpacking, together with minimizing
chromatographic resin losses.
The standard column volume (CV) is
240 and 260 litres respectively at a
separation distance of 13,5 cm. In principle,
up to 2000 litres of resin volume
per column are possible. For milk applications,
this will allow processing flow
rate of ~15,000 litres per hour.
Axial- vs. Radial Flow Column
While an axial flow column design offers
the advantage of a higher flexibility
in the separation distance, the radial
flow column has much more to offer.
Below are the specifications for a radial
flow column, which make a radial
flow column superior to an axial flow
column:
• Reduced pressure drop of 20 - 50 %
• Improved loading efficacy
• Reduced feed handling complexity
• High binding kinetics (dynamic binding
capacity)
• High process robustness (larger process
tolerance window)
• Higher throughput
• Higher efficiency
• Higher purity.
Is it possible to convert
existing Processes from Axial
to Radial Flow Columns?
A conversion from an axial to a radial
flow column is possible as long as the
required separation distance for the effcient
separation is max. 13.5 cm, which
is in most of the ion-exchange based
chromatography processes the case.
The change from axial to radial can be
justified as described above: radial flow
columns have significantly lower pressures
than axial columns. This means
that the column can be operated at a
higher flow rate, resulting in a higher
throughput and, in relation to time, a
higher turnover.
How to extract lactoferrin
from milk
For the industrial extraction of the protein
lactoferrin from milk and whey,
radial flow column based chromatography
plants are used. The whole milk
is collected at dairy farms and stored
in refrigerated conditions until quality
test passed and transported to
a dairy processing facility. Once the
milk arrived to dairy facility, it undergoes
cream separation to remove fat
and collect skim milk. Then the skim
milk goes through a pasteurizer to kill
pathogenic bacteria before any further
process. For bovine lactoferrin (bLF) extraction,
the ideal option is to extract
the lactoferrin before the pasteurizer
process step. In such cases, skim milk
Technology/IT ¦ IDM
Example for axial- and radial flow chromatography
flow patterns
is pumped through a chromatography
column packed with SP SepharoseTM
Big Beads Resin (e.g. cross-linked agarose)
until the maximum binding capacity
of the resin has been reached.
The column is then washed with water
and low salt buffers, before the
bovine lactoferrin is eluted by applying
a buffer with high salt solution.
Afterwards the resin in the column is
regenerated for next purification cycle
by a CIP procedure using sodium hydroxid
(NaOH). The purified lactoferrin/
salt solution is further processed
to remove the salt and concentrate
the solution by diafiltration (DF) and
ultrafiltration (UF). Subsequently the
LF concentrate undergoes a pasteurization
step to kill pathogenic bacteria,
followed by microfiltration to remove
any particulates. LF is further concentrated
using a second UF process step
and then dried using freeze-drying or
spray drying technologies. The powder
is formulated and packed to a desired
pack size.
Process flow of lactoferrin extraction
Radial throughflow
November/December 2020 ¦ international-dairy.com · 35
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