SIMPLE METHOD FOR SIMULTANEOUS REMOVAL OF MULTIPLE IMPURITIES
FROM CULTURE SUPERNATANTS TO ULTRALOW LEVELS
Reference to Related Applications
This application claims priority to U.S. Provisional Application No. 61/327,238 of the
same title filed April 23, 2010, the entirety of which is hereby incorporated by reference.
Background
1. Field of the Invention
This invention is directed to a method for simultaneously removing, preferably in one
step, multiple impurities from crude sample containing products produced by cell culture or
fermentation and, in particular, the removal of contaminants such as media components,
proteins, nucleic acids, lipids, and lipopolysaccharides to ultralow levels. The product may be
produced by yeast, bacterial or mammalian cells with impurities reduced to ultralow level of
91% to 99.9 % as compared to the purified target substance. The invention is also directed to
the products that have been purified according to this method.
2. Description of the Background
Polysaccharides, proteins and nucleic acids are synthesized by various organisms such
as yeast, bacteria, and mammalian cells, which can be produced by fermentation for
commercial purpose in the applications of human, veterinary or diagnostic use. Industrial
production of biotechnological product from these organisms is primarily done by
fermentation in the applications of products for human, veterinary or diagnostic use. In
addition to biosynthetic products produced during fermentation, media nutrients and
components also contribute contaminants. It is generally necessary to produce extremely pure
products with ultra-low levels of impurities like protein, lipid, nucleic acid and
lipopolysaccharides from crude starting materials such as fermentation fluids. In addition to
biosynthetic products produced during fermentation, media nutrients also contribute
contaminants. Product purification typically involves multiple and complex steps to reduce
impurity levels to acceptable levels. Conventional processes for removing impurities include
extraction, chromatography, precipitation, ultra-filtration, and many others. Multiple and
complex steps adversely affect yield, quality, stability, processing time and process
operations. Further, these processes are expensive to run, require a high degree of skill to
perform, and a significant amount of time to reduce impurity levels.
United States Patent No. 5,747,663 relates to a process for reduction or removal of
endotoxin from biotechnologically derived therapeutic compositions. The process has
incorporated incubation with non-ionic detergent prior to chromatographic purification. The
chromatographic medium claimed is anion exchange material. The chromatographic
purification involves use of sodium chloride salt for washing.
United States Patent No. 6,428,703 relates to a process for reduction or removal of
endotoxin from biological macromolecules. The process has incorporated treatment with
non-ionic detergent without incubation period prior to the chromatographic purification. The
chromatographic medium is anion exchange material. The other element is the anion
exchanger retains the macromolecules and the purified macromolecule is eluted from the
exchanger.
Conventional purification procedures are limited and do not result in products with
ultra-low levels of impurities without extensive effort. Thus, there exists a need to develop a
simple purification method to achieve high purity with ultralow levels of impurities of such
biosynthetic products from culture supernatants, cell extracts, plant extracts or crude lysate.
Summary of the Invention
The present invention overcomes the problems and disadvantages associated with
current strategies and designs, and provides new tools and methods for simultaneous removal
of multiple contaminants from culture supernatants, cell extracts, plant extracts or crude
lysate. The method may also be applied to partially purified products to reduce the
contaminants or undesired impurities to ultralow levels. Ultralow levels of impurities are
levels that are preferably from 91% to 99.9% reduced as compared to unpurified substances.
The invention may also be used in conjunction with additional purification steps to further
enhance the purity of the target and reduce the level of contaminants.
One embodiment of the invention is directed to a purification process comprising:
contacting a mixture containing a target substance and one or more contaminants to a
chromatography matrix; washing the bound target substance with one or more buffers
preferably at least one of which comprises a synergistic combination of a lyotropic agent or an
organic solvent, a detergent, and a salt component; desorbing the bound target substance from
the matrix, and collecting the target substance wherein the concentration of the one or more
contaminants is preferably reduced by 91% to 99.9% as compared to the mixture. Preferably
the target substance is one or more of an anionic polysaccharide, an anionic protein, a protein,
a polysaccharide, an anionic molecule, a cationic molecule, or a nucleic acid, and the mixture
contains one or more contaminants derived from yeast, bacteria, or cell culture fermentation,
which may include media components, nucleic acids, proteins, lipids, and/or
lipopolysaccharides.
Also preferably the chromatography matrix is or contains an anion exchange
chromatography sorbent, a cation exchange chromatography sorbent, a hydrophobic
interaction chromatography sorbent, mixed mode chromatography sorbent or a Cibacron-Blue
pseudoaffinity chromatography sorbent or resins. Alternatively, the chromatography matrix
may be a non sorbent chromatography such as a membrane or monolith chromatography
devices. Accordingly, the chromatography matrix may involve anionic, cationic, hydrophobic
or mixed mode sorbents as media or membrane. Washing may involve one, two, three or
more buffers, wherein washing is performed sequentially or independently. Preferably the
first buffer contains from 2 to 30% isopropanol, 10 to 2,000 mM of salt, and 0.01 to 1%
Triton X-100 at a suitable pH. Preferably the second buffer contains 1 to 8 molar urea, 10 to
2,000 mM of salt, and 0.01 to 1% Triton X-100 at a suitable pH. Preferably the third buffer
contains a salt concentration different than the concentration of salt of the eluent depending in
part on the chemical or physical characteristics of the target substance and also the
chromatography matrix.
The bond target is desorbed preferably with an eluent containing a salt concentration
that is different than the salt concentration of one or more of the wash buffers. Preferably the
concentration of the one or more contaminants in the eluate is substantially reduced as
compared to the concentration or amount of contaminants in the mixture before purification.
More preferred, reduction is at least 91% and more preferably from 91% to 99.9% reduced.
Also preferably the chromatography matrix contains an anion exchange
chromatography sorbent. Anionic species are acidic and have a negative charge.
Contaminants, such as lipids, lipopolysaccharides, nucleic acids (e.g. are highly charged with
repeating ionic groups, as are the anionic polysaccharides), are also anionic species as are
many host cell proteins and media contaminants. The method of the invention purifies
anionic target products despite this similarity in charge.
Another embodiment of the invention is directed to process for the purification of a
target comprising: adsorbing a mixture containing the target and one or more contaminants to
an ion exchange chromatography matrix, wherein at least one of the one or more
contaminants comprises an endotoxin; washing the bound target with one or more wash
buffers wherein at least one wash buffer contains a synergistic combination of a lyotropic
agent or an organic solvent, a detergent and a salt component; desorbing the bound target
from the chromatography matrix; and collecting the desorbed target wherein the level of
endotoxin is less than or equal to 3 UE/mg of target and preferably less than or equal to 2.5
UE/mg of target. Preferably the amount of the one or more contaminants is in the desorbed
target is reduced by 91% to 99.9%, and washing involves only a single wash buffer.
Another embodiment of the invention is directed to a purified target substance
obtained from the methods of the invention. Preferred targets include, for example, a
meningococcal C polysaccharide, Haemophilus influenzae type b (Hib) polysaccharide,
recombinant erythropoietin protein, or recombinant CRM197.
Other embodiments and advantages of the invention are set forth in part in the
description, which follows, and in part, may be obvious from this description, or may be
learned from the practice of the invention.
Description of the Invention
The present invention relates to the field of purification of biological products,
particularly purification of substances from crude culture samples such that extremely low
levels of contaminating materials remain. The purified substance may be, for example,
proteins, polysaccharides, virus or nucleic acids that are used in the preparations of medicines
for the treatment of diseases, vaccines, therapeutic drugs and diagnostic kits and components,
which may be useful for humans or other animals.
The invention is directed to product purification processes that are performed
preferably in one-step for the simultaneous removal of multiple impurities and particularly, to
purification from bacterial, yeast, plant and other cell cultures and fluids such that the final
products obtained contain extremely low levels of contaminating substances. These
contaminants include but are not limited to one or more of proteins, lipids, nucleic acids,
endotoxin, cell debris, and lipopolysaccharides. The invention comprises processes for
purification of a desired product from a mixture such as, for example, a cell lysate, a cell
extract, a cell culture or other crude sample which may be bacterial (prokaryotic) or cellular
(eukaryotic) in origin. The target molecule or substance is preferably a protein,
polysaccharide or nucleic acid that preferentially adsorbs or binds to the chromatography
matrix. The chromatography matrix may be a single form of chromatograpy material or a
combination of materials, for example, arranged in a step-like configuration. Binding may be
through ionic, hydrophobic or hydrophilic interaction. Preferred chromatography matricies
include, but are not limited to an ion exchange matrix such as a Sepharose, Cibacron Blue
affinity media, or a mixed mode chromatography matrix. The one or more washes
preferentially involve simultaneous use of urea/detergent/salt and/or solvent/detergent/salt in
the various washes on the column prior to the elution of desired product. The preferred
method of the invention involves an ion exchange matrix such as Q-Sepharose, a washing
agent such as urea or isopropanol, detergent such as Triton X-100, and salt such as sodium
chloride in the one or more chromatographic wash buffers. The eluate is then collected and
contains highly purified target substance with an ultra-low level of impurities. This method
can be applied to polysaccharides, proteins or nucleic acids of interest derived from
recombinant or wild yeast, bacteria or mammalian cell lines and extracellular, periplasmic or
intracellular product. The synergistic effect of concomitant use of these components in wash
buffers allows for the removal of multiple contaminants during the washing step on
chromatographic sorbents and leads to highly pure product in the eluate.
The invention is directed to a purification process preferably comprising the steps of:
(1) binding of a mixture containing the target substance and one or more contaminants to a
chromatography matrix; (2) washing the bound target substance with one or more buffers
containing a combination of a lyotropic agent or organic solvent, a detergent, and a salt
component; (3) desorbing the target substance from the chromatography matrix which may be
with an elution buffer (the eluent); and (4) collecting the target in the eluate wherein the
eluate preferentially contains target with ultra low levels of contaminants. Binding involves
preferential adsorption of the target to the matrix through ionic, hydrophobic, hydrophilic or
covalent interaction. Preferably the washes are given sequentially or any single wash may be
performed independently. Further, one or more of these washes may be followed by another
wash of salt buffer with salt concentration different than elution buffer before the elution of
product of interest, depending on the product of interest. Target is collected in the eluate
upon contacting a deadsorbing eluent to the target-bound chromatography matrix. The
resulting eluate contains increased concentrations of target and ultra-low concentrations of
contaminants. Ultra low levels of contaminants are substantial reductions of impurities that
were present in the starting material (e.g. the target substance with impurities). Substantial
reductions are preferably reductions of 85% or greater, more preferably 90% or greater, more
preferably 95% or greater, and still more preferably in the range of 91% to 99.9%, and even
more preferably to the degree that impurities are undetectable by convention and industry
standard detection methods and devices.
A significant feature of the purification method is the synergistic effect on
simultaneous removal of multiple contaminants with the concomitant use of solvent, urea,
detergent and salt during the washing step on chromatographic sorbent. Typical contaminants
include media and other components that were introduced to a culture to stimulate growth as
well as nucleic acids, proteins, lipids, nucleic acids, and lipopolysaccharides, and any other
unwanted or undesirable substance that may be present in the material to be purified.
The method of the invention involves simultaneous reduction of anionic
lipopolysaccharide like endotoxin as well as protein, and nucleic acid contaminants from
culture supernatant to ultra low levels. An incubation step is not always necessary prior to
chromatographic purification, and preferably not required. Endotoxin levels can be reduced
to ultra low level such as, preferably, 3 UE/mg or less as compared to conventional processes
which are only able to achieve low levels of endotoxin with considerable effort. Preferably
endotoxin levels are reduced to 2.5 UE/mg or less, and even more preferably to 2.0 UE/mg
less. The method of the invention is also less time consuming, cost effective, reproducible as
compared to conventional approaches.
The invention is preferably directed to a process for purification of a desired product
by ion exchange chromatography with simultaneous treatment with urea/detergent/salt and/or
solvent/detergent/salt in the various washes on the column prior to the elution of the desired
product. Conventional chromatography sorbents may be used for purification as well as well
as membrane and monolith devices. Preferred anion ion exchange matrices include, but are
not limited to Q Sepharose, DEAE Fast Flow (GE Healthcare), and Q HyperCel (Pall Life
Sciences), all of which are commercially available. Examples of preferred cation exchange
matrices include, but are not limited to S Sepharose, CM Sepharose, S Source (GE
Healthcare, CM Ceramic and S HyperCel (Pall Life Sciences). Examples of mixed mode
sorbents include, but are not limited to MEP, HEA PPA HyperCel (Pall Life Sciences),
Ceramic hydroxyapatite (Bio-Rad) and MMC (GE Healthcare). Examples of Cibacron blue
dye-ligand pseudoaffinity chromatography sorbent include Blue-Sepharose (GE Healthcare).
Examples of suitable membranes include, but are not limited to Q and S Sartobind and
Mustang devices (Sartorius and Pall Life Sciences, respectively), and Phenyl Sartobind
hydrophobic interaction membrane (Sartorius). A variety of suitable monolith
chromatography devices are also available (BIA Separations, Wilmington, Delaware).
Examples of preferred lyotropic agents include urea, guanidine hydrochloride,
arginine and sodium thiocyanide. Examples of preferred detergents include Triton X-100,
Polysorbate 20, Polysorbate 80, sodium dodecyl sulfate (SDS), and sodium sarcosine.
Examples of preferred organic additives include ethanol, isopropanol (IPA), glycerol ethylene
glycol, and propylene glycol. Examples of preferred salts include sodium chloride, potassium
chloride, ammonium sulfate and sodium phosphate. Again, all of the aforesaid agents,
detergents, additives, and salts are well-known and commercially available.
Products that are purified according to the method of the invention include ones which
may be obtained from a large variety of biological fluids including yeast, bacteria, plant, and
cell culture fermentation and, preferably, bacterial cell supernatants. Preferably, products
purified are involved in the manufacture of therapeutic proteins, vaccines and may include
anionic polysaccharides, anionic protein, and nucleic acids. Additional products that can be
purified by the methods of the invention include, but are not limited to, culture supernatants of
eukaryotic cells and biological samples of serum and other bodily fluids that are utilized in
medical procedures.
Preferred bacterial products that can be purified using the methods of the invention
include, for example, Neisseria meningiditis serotype B alpha 2-8 linked polysaccharide,
Neisseria meningiditis serotype C capsular polysaccharide, Salmonella Vi polysaccharide ,
delipidataed lipopolysaccahrides and lipooligosaccharides, and Haemophilus influenzae type
B -PRP capsular polysaccharide. These examples are polysaccharides used for vaccine
preparations and, therefore, preferably have ultra low levels of impurities to meet or exceed
guidelines established by the U.S. Food and Drug Administration and similar authorities
around the world. Preferred protein products that can be purified using the methods of the
invention include, for example, recombinant erythropoietin from cell culture fermentation and
recombinant cross reacting material 197 from bacterial fermentation.
According to the method of the invention, the product may be purified from cells
containing product or from the culture supernatant, or both. The cells and culture supernatant
are preferably separated by either centrifugation or cross flow filtration. For extracellular
product, the culture supernatant is preferably directly processed through the method of
invention, whereas for intracellular or periplasmic space product, products are preferably
recovered from both culture supernatant and/or cells. The protein is extracted from the cells
by chemical means like osmotic shock in sucrose or physical means like homogenization.
Culture supernatant and/or extract or lysate containing product is then preferably processed
through chromatographic purification step.
Most of the polysaccharides from bacterial fermentation and mammalian cell
recombinant proteins are derived from supernatant whereas other recombinant proteins and
nucleic acid are derived from cells of yeast and bacteria.
Chromatography Step
This purification step comprises ion exchange, hydrophobic interaction, Cibacron Blue
pseudo-affinity or mixed mode chromatography sorbent in a column mode or batch mode. For
example, for anion exchange Q-Sepharose may be used, and phenyl Sepharose sorbent for
hydrophobic interaction. Either of the following mentioned washes or in combination can be
given, order of wash sequence can also be altered appropriately.
Column preparation
A column is packed according to the manufacturer instructions. The column is
sanitized and equilibrated with equilibration buffer until stable baselines for RI, absorbance m
and conductivity are obtained. For ion exchange low molarity suitable Equilibration Buffer is
used with desired pH like 20 mM Tris buffer (pH 8) and phosphate buffer (pH 7) whereas for
hydrophobic interaction the buffer has a high salt content e.g., 2.5 M NaCl.
Column loading (Crude sample)
Culture supernatant is adjusted to desired conductivity and pH by addition of
acid/alkali/buffer/water/salt. The column is then loaded with culture supernatant or lysate or
extract containing sample at a recommended flow rate. After loading, the column is washed
again with equilibration buffer to remove any residual material not tightly bound to the
sorbent.
Column Wash I (Solvent)
The column is washed with suitable column volumes of Wash Buffer-I containing
appropriate concentrations of solvent like isopropanol, detergent such as preferably Triton X-
100 and salt such as preferably NaCl in an Equilibration Buffer at a suitable flow rate until
stable baselines for Refractive index, Absorbance and conductivity are obtained to monitor
protein, nucleic acid, lipid and lipopolysaccharide impurities.
Column Wash II (Lyotropic agent)
The column is washed with suitable column volumes of Wash Buffer-II containing
appropriate concentrations of chaotropic agent like urea, detergent like Triton X-100 and salt
like NaCl in an equilibration buffer at a suitable flow rate until stable baselines for Refractive
index, Absorbance and conductivity are obtained.to remove any protein, nucleic acid, lipid
and lipopolysaccharide impurities.
Column Wash III (Salt)
The column is washed with suitable column volumes of Wash Buffer III containing
appropriate concentration of salt like NaCl different to that of elution concentration in an
equilibration buffer at a suitable flow rate until stable baselines for Refractive Index,
absorbance and conductivity are obtained to monitor removal of protein, nucleic acid and
lipopolysaccharide impurities.
Elution step (Product)
Desired product is eluted from the column with Elution Buffer containing appropriate
concentration of salt or any other elution agent at a suitable flow rate. Elution may be
monitored using refractive index or Absorbance detection. Appropriate column volumes of
Elution Buffer is collected which contains the desired product. Column can be regenerated by
passing appropriate buffer with salt and sanitizing agent like sodium hydroxide. It thus
removes multiple impurities, different in nature, in a simple method of purification, preferably
in a single step, on a chromatography sorbent.
The following examples illustrate embodiments of the invention, but should not be
viewed as limiting the scope of the invention.
Examples
As indicated herein, the invention is illustrated for the single method of simultaneous
removal of multiple impurities from crude samples of culture supernatant to ultralow level by
chromatographic techniques. In one method of the invention, the adsorption sorbents are
anion exchangers with specific elution conditions such that the resultant purified product
exhibits a very low content of contaminating protein, lipid, nucleic acid and
lipopolysaccharide.
Example 1: Meningococcal C Polysaccharide.
Capsular polysaccharide was derived from bacterial fermentation. The culture
supernatant containing products was obtained by centrifugation or cross flow filtration of
fermentation broth.
Anion Exchange Chromatography Sorbent: Q-Sepharose
Buffers: Equilibration Buffer (20 mM Phosphate buffer pH 7.5)
Wash Buffer-I (15% IPA+0.25% Triton X-100+0.3 M NaCl, pH 7.5)
Wash buffer-II (6 M Urea+0.25% Triton X-100+0.3 M NaCl, pH 7.5)
Wash Buffer III (20 mM phosphate buffer+0.3 M NaCl, pH 7.5)
Elution buffer (20 mM Phosphate buffer, 0.5 M NaCl, pH 7.5)
Regeneration Buffer ( 1 M NaCl and 0.5 M NaOH)
A column with 20 cm inner diameter (Pharmacia, BPG 200/500) was packed
according to the manufacturer instructions using 6 L Pharmacia Q Sepharose Fast flow
sorbent with a fixed bed height of -200 mm. The column was washed with 10 column
volumes (CV) of water for Injection (WFI) and then charged and sanitized using 5 CV of 1M
sodium chloride solution with 0.5 M NaOH solution using the flow rates recommended by the
manufacturer.
Column loading
Culture supernatant was adjusted to pH 7.5 by acid/alkali addition and conductivity to
< 10 mS/cm by water for injection dilution. The column was neutralized with Equilibration
Buffer (20 mM Phosphate buffer pH 7.5), for -15 CV until stable baselines for A2 0 m and
conductivity were obtained. The column was then loaded with culture supernatant containing
sample at a flow rate of 60 cm/h. After loading, the column was washed again with 3 CV of
equilibration buffer (20 mM Phosphate buffer pH 7.5) to remove any residual material not
tightly bound to the sorbent.
Column Wash I
The column was washed with 3 CV of Wash Buffer-I (15% IPA+0.25% Triton X-
100+0.3 M NaCl, pH 7.5) at a flow rate of 60 cm/h until stable baselines for Refractive index,
280 and conductivity was obtained to remove any protein, nucleic acid, lipid and
lipopolysaccharide impurities.
Column Wash II
The column was washed with 3 CV of Wash buffer-II (6 M Urea+0.25% Triton X-
100+0.3 M NaCl, pH 7.5) at a flow rate of 60 cm/h until stable baselines for Refractive index,
280 and conductivity were obtained to further remove any protein, nucleic acid, lipid and
lipopolysaccharide impurities.
Column Wash III
The column was washed with 3 CV of Wash Buffer III (20 mM phosphate buffer+0.3
M NaCl, pH 7.5) at a flow rate of 60 cm/h until stable baselines for Refractive index, A 2 0
and conductivity were obtained to further remove any protein, nucleic acid and
lipopolysaccharide impurities.
Elution step
Men C polysaccharide product was eluted from the column with Elution Buffer (20
mM Phosphate buffer, 0.5 M NaCl, pH 7.5) at a flow rate of -60 cm/h in the form of a single
Refractive index/A2 24 peak. Continue elution until Refractive index/A224nm absorbance began
to decrease below 5 % of the peak value. About 2 column volumes of Elution Buffer were
used in this elution step. The column was regenerated by passing 1 M NaCl with 0.5 N
NaOH.
Protein, DNA, lipid, lipopolysaccharide, host cell protein, host cell DNA and target
polysaccharide analysis was performed on samples of the load, and eluate taken during the
chromatographic run. Polysaccharide and protein were assayed using standard methods,
polysaccharide using phenol sulfuric acid method, nucleic acid by absorbance at 260 nm, lipid
by orcinol method and protein using Lowry method. Host cell DNA was analyzed by RTPCR
whereas host cell protein assayed by ELISA. Lipopolysaccharide was determined using
a kinetic turbidimetric assay for endotoxin. From Lipopolysaccharide standards, value for
unknown sample was derived in units of EU/ml. Results are shown in Table 1.
TABLE 1
As can be determined in Table 1, the Q-Sepharose column reduced the
Lipopolysaccharide level from initial 100,000 EU/mg polysaccharide to less than or equal to 5
EU/mg LPS in the eluate. The target polysaccharide was bound to the sorbent and recovery
was 70% based on assay results. Polysaccharide eluted off of the column in 20 mM
phosphate buffer, 0.5 M NaCl, pH 7.5. Analysis showed that most of the nucleic acid and
lipopolysaccharide was bound to the sorbent, but came off during the washing steps. The
majority of small media proteins and lipids did not bind to the matrix and were found in the
flow through. Significantly, the polysaccharide purity was more than 99% in the final
product.
Example 2: Haemophilus influenzae type b (Hib) polysaccharide.
The culture supernatant containing product was obtained by centrifugation or cross
flow filtration of fermentation broth to separate the bacterial cells. Supernatant obtained
containing polysaccharide with impurities was processed through one step method of
purification.
Anion exchange chromatography: Sorbent: Q-Sepharose
Buffers: Equilibration Buffer (20 mM Phosphate buffer pH 7.5)
Wash Buffer-I (15% IPA+0.25% Triton X-100+0.3 M NaCl, pH 7.5)
Wash buffer-II (6 M Urea+0.25% Triton X-100+0.3 M NaCl, pH 7.5)
Wash Buffer III (20 mM phosphate buffer+0.3 M NaCl, pH 7.5)
Elution buffer (20 mM Phosphate buffer, 0.5 M NaCl, pH 7.5)
Regeneration Buffer ( 1 M NaCl and 0.5 M NaOH)
A column with 20 cm inner diameter (Pharmacia, BPG 200/500) was packed
according to the manufacturer instructions using 6 L Pharmacia Q Sepharose Fast flow
sorbent with a fixed bed height of -200 mm. The column was washed with 10 column
volumes (CV) of water for Injection (WFI) and then charged and sanitized using 5 CV of 1M
sodium chloride solution with 0.5 M NaOH solution using the flow rates recommended by the
manufacturer.
Column loading
Column was neutralized with Equilibration Buffer (20 mM Phosphate buffer pH 7.5), for
15 CV until stable baselines for Refractive index, A2 0 m and conductivity are obtained. Culture
supernatant was adjusted to pH 7.5 by acid/alkali addition and conductivity to less than or equal to
10 mS/cm by water for injection dilution. The column was then loaded with culture supernatant
containing sample at a flow rate of 60 cm/h. After loading, the column was washed again with 3
CV of equilibration buffer (20 mM Phosphate buffer pH 7.5) to remove any residual material not
tightly bound to the sorbent.
Column Wash I
The column was washed with 3 CV of Wash Buffer-I (15% IPA+0.25% Triton X-
100+0.3 M NaCl, pH 7.5) at a flow rate of 60 cm/h until stable baselines for Refractive index,
A2 80 and conductivity was obtained to remove any protein, nucleic acid, lipid and
lipopolysaccharide impurities.
Column Wash II
The column was washed with 3 CV of Wash buffer-II (6 M Urea+0.25% Triton X-
100+0.3 M NaCl, pH 7.5) at a flow rate of 60 cm/h until stable baselines for Refractive index,
A2 0 and conductivity were used to monitor protein, nucleic acid, lipid and
lipopolysaccharide impurities.
Column Wash III
The column was washed with 3 CV of Wash Buffer III (20 mM phosphate buffer+0.3 M
NaCl, pH 7.5) at a flow rate of 60 cm/h until stable baselines for Refractive index, A2 o m and
conductivity was obtained to further remove any protein, nucleic acid, lipid and lipopolysaccharide
impurities.
Elution step
Polysaccharide was eluted from the column with elution buffer (i.e. eluent) (20 mM
phosphate buffer, 0.5 M NaCl, pH 7.5) at a flow rate of -60 cm/h in the form of a single
Refractive index/A224 peak. Continue elution until Refractive index/A absorbance began
to decrease below 5 % of the peak value. About 2 column volumes of eluent are necessary in
this elution step. The column was regenerated with 1M NaCl with 0.5 N NaOH.
The process reduced the lipopolysaccharide level to less than 3 EU/mg
polysaccharide. The polysaccharide recovery was 60% based on assay results, which was
bound to the sorbent. Polysaccharide eluted off of the column in 20 mM phosphate buffer,
0.5 M NaCl, pH 7.5. Analysis showed that most of the nucleic acid and lipopolysaccharide
were bound to the sorbent, but came off during washing steps. The results achieved are
shown in Table 2.
TABLE 2
Protein, DNA, lipid, lipopolysaccharide, host cell protein, host cell DNA and desired
polysaccharide analysis was performed on samples of the load, and eluate taken during
chromatographic run. The target polysaccharide and residual protein were assayed with
standard methods, polysaccharide using phenol sulfuric acid method, nucleic acid by
absorbance at 260 nm, lipid by the orcinol method and protein using Lowry method. Host
cell DNA analyzed by RT-PCR and host cell protein by ELISA. Lipopolysaccharide was
assayed by kinetic turbidimetric assay for endotoxin. Using lipopolysaccharide standards, the
value for unknown sample was derived in units of EU/ml.
The majority of small media proteins and lipids were in the flow through. This elution
fraction was processed further by diafiltration for the removal of salt as desired. The
polysaccharide purity obtained was more than 99%.
Example 3: Recombinant erythropoietin protein.
The culture supernatant containing product was obtained by cross flow filtration of
fermentation broth to separate the cells. Supernatant obtained containing protein with media
components and impurities was processed through one step method of purification. The
culture used was recombinant mammalian cell CHO cell line for erythropoietin production.
Hydrophobic interaction chromatography: Sorbent: TOYOPEARL® (Toyopearl-butyl;
Tosohas)
Buffers: Equilibration Buffer (20 mM Phosphate buffer pH 7.2, 0.75 M NaCl)
Wash buffer (19% IPA+0.75 M NaCl, pH 7.2)
Elution buffer (27% IPA+0.75 M NaCl, pH 7.2)
Regeneration Buffer ( 1 M NaOH)
A column with 20 cm inner diameter (GE, BPG 200/500) was packed according to the
manufacturer instructions using 6 L GE Butyl Sepharose sorbent with a fixed bed height of
-200 mm. The column was washed with 10 column volumes (CV) of water for Injection
(WFI) and then sanitized using 5 CV of 0.5 M NaOH solution using the flow rates
recommended by the manufacturer.
Column loading
Column was neutralized with Equilibration Buffer (27% IPA, 20 mM phosphate buffer pH
7.2 and 0.75 M NaCl), for 15 CV until stable baselines for Refractive index, A2 o m and
conductivity were obtained. The column was then loaded with culture supernatant containing
sample at a flow rate of 60 cm/h. Culture supernatant was adjusted to pH 7.2 by acid/alkali
addition and conductivity to greater than or equal to 200 mS/cm by sodium chloride addition.
After loading, the column was washed again with 3 CV of equilibration buffer to remove any
residual material not tightly bound to the sorbent.
Column Wash
The column was washed with 3 CV of Wash Buffer-I (17% IPA+0.75 M NaCl, pH
7.2) at a flow rate of 60 cm h until stable baselines for A2 80 and conductivity were
obtained.to remove any protein, nucleic acid, lipid and lipopolysaccharide impurities.
Elution step
Protein was eluted from the column with Elution Buffer (20 mM Phosphate buffer, pH
7.5) at a flow rate of -60 cm/h in the form of a single A224 peak. Elution was continued until
A224nm absorbance begins to decrease below 5 % of the peak value. About 2 column volumes
of Elution Buffer are necessary in this elution step. The column was regenerated by passing 1
N NaOH through as a Regeneration Buffer.
As shown in Table 3, lipopolysaccharide level was reduced from 120,000 EU/mg
polysaccharide to less than or equal to 2.3 EU/mg polysaccharide. The protein recovery was
80% which is bound to the sorbent. Protein eluted off the column in 20 mM Phosphate
buffer, pH 7.5. Analysis showed that most of the nucleic acid and polysaccharide were not
bound to the sorbent, and bound lipopolysaccharides come off during washing steps.
TABLE 3
The majority of small media proteins and lipids came off during the washes. The
protein purity obtained was more than 99%.
Example 4: Recombinant CRM197.
Recombinant protein CRM197, cross reacting material, a mutant of diphtheria toxin,
was derived from bacterial fermentation. As the protein was located in periplasmic space,
product was recovered from both culture supernatant and cells. The cells and culture
supernatant were separated by either centrifugation or cross flow filtration. The protein was
extracted from the cells by chemical means like osmotic shock in sucrose or physical means
like homogenization. Supernatant and/or extract containing product was then processed
through chromatographic purification step as follows.
1. Anion Exchange Chromatography: Sorbent: CaptoQ
Buffers: Equilibration Buffer (15 mM Tris buffer pH 8)
Wash Buffer-I (5% IPA+0.05% Triton X-100+0.05 M NaCl, 15 mM Tris pH
8)
Wash Buffer-II (15 mM Tris buffer + 0.08 M NaCl, pH 8)
Elution buffer (15 mM Tris + 0.2 M NaCl, pH 8)
Regeneration Buffer (1.5 M NaCl and 1M NaOH)
Cells obtained from 20 L fermentor were subjected to extraction by osmotic shock
using 30% Sucrose, 15 mM Tris pH 7.4, 5 mM EDTA and 50 mM Tris pH 7.4. The filtered
extract (45L) was loaded on Capto-Q sorbent in 10 mM Tris buffer pH 8.0 and eluted using
0.2 M NaCl in 10 mM Tris buffer pH 8. A column with 30 cm inner diameter (GE, BPG
300/500) was packed according to the manufacturer instructions using 10 L Capto Q (GE)
sorbent. The column was washed with 3 column volumes (CV) of water for Injection (WFI)
and then charged using 0.5 CV of 1 M Tris pH 8 with flow rates as recommended by the
manufacturer.
Column loading
The column was equilibrated with Equilibration Buffer (15 mM Tris buffer pH 8), for
about 1 CV until stable baselines for A2 o m and conductivity were obtained. The column was
then loaded with filtered extract containing sample at a flow rate of 212 L/h (240 cm/h). After
loading, the column was washed again with about 1 CV of equilibration buffer (15 mM Tris
buffer pH 8) to remove any residual material not tightly bound to the sorbent.
Column Wash I
The column was washed with 2 CV of Wash Buffer-I (5% IPA+0.05% Triton X-
100+0.15 M NaCl, pH 7.5) at a flow rate of 240 cm h until stable baselines for A28onm and
conductivity were obtained.to remove any protein, nucleic acid, lipid and lipopolysaccharide
impurities. The column was washed again with ~2 CV of equilibration buffer (15 mM Tris
buffer pH 8).
Column Wash II:
The column was washed with 2 CV of Wash buffer-II (15 mM Tris buffer + 0.08 M
NaCl, pH 8) at a flow rate of 240 cm/h until stable baselines for A2 o m and conductivity are
obtained to further remove any protein and nucleic acid impurities.
Elution step
Protein product was eluted from the column with Elution Buffer (15 mM Tris + 0.2 M
NaCl, pH 8) at a flow rate of 240 cm/h in the form of a single A2 o peak. Continue elution
until A2g0nm absorbance begins to decrease below 5 % of the peak value. About 2 column
volumes of Elution Buffer were necessary in this elution step. Column was regenerated by
passing 2 column volumes of 1.5 M NaCl with 1N NaOH.
2. Hydrophobic Interaction Chromatography: Sorbent: Phenyl Sepharose
Buffers: Equilibration Buffer (10 mM phosphate buffer pH 7.4 + 1.5 M NaCl)
Wash Buffer-I ( 1 M NaCl+10 mM phosphate buffer pH 7.4)
Wash Buffer-II (0.3 M NaCl + 10 mM phosphate buffer pH 7.4)
Elution buffer (10 mM phosphate buffer pH 7.4)
Regeneration Buffer (20% IPA)
The Capto-Q IEC eluate was loaded on Phenyl Sepharose sorbent in 10 mM phosphate
buffer pH 7.4 and eluted using 10 mM phosphate buffer pH 7.4. A column with 30 cm inner
diameter (GE, BPG 300/500) was packed according to the manufacturer instructions using 10
L Phenyl Sepharose (GE) sorbent.
Column loading
Column was equilibrated with Equilibration Buffer (10 mM phosphate buffer pH 7.4 +
1.5 M NaCl), for ~ 1 CV until stable baselines for A2 o m and conductivity were obtained. The
column was then loaded with IEC eluate containing sample at a flow rate of 150 cm/h. After
loading, the column was washed again with ~ 1 CV of Equilibration Buffer (15 mM Tris buffer
pH 8) to remove any residual material not tightly bound to the sorbent.
Column Wash I
The column was washed with 2 CV of Wash Buffer-I (51 M NaCl+10 mM phosphate
buffer pH 7.4) at a flow rate of 150 cm h until stable baselines for A2 0 and conductivity
were obtained.to remove any protein, lipid and lipopolysaccharide impurities. The column
was washed again with about 2 CV of Equilibration Buffer.
Column Wash II
The column was washed with 2 CV of Wash buffer-II (0.3 M NaCl + 10 mM
phosphate buffer pH 7.4) at a flow rate of 150 cm/h until stable baselines for A o m and
conductivity were obtained.to further remove any protein and lipid impurities.
Elution step
Protein product was eluted from the column with Elution Buffer (10 mM phosphate
buffer pH 7.4) at a flow rate of 150 cm/h in the form of a single A2 o peak. Continue elution
until A
80nm
absorbance begins to decrease below 5 % of the peak value. About 2 column
volumes of Elution Buffer were necessary in this elution step. Column was regenerated by
passing 2 column volumes of 20% IPA.
The method of purification involving Capto-Q and Phenyl Sepharose column reduced
the lipopolysaccharide level to less than or equal to 100 EU/mg protein. Analysis showed that
nucleic acid, protein impurities, lipids and polysaccharides come out in the various washes on
Capto-Q sorbent. Resultant purified protein was highly pure due to combination of two
chromatography steps involving washing steps of method of invention. A single step of
chromatography (Capto-Q) alone with washing steps of method of invention leads to more
than 85% purity. The target protein purity obtained was more than 99.9% with host cell
protein less than 100 ng per mg protein and host cell DNA less than 50 ng per mg protein.
Example 5: Recombinant CRM197 with Cibacron-Blue.
Recombinant protein CRM197, cross reacting material, a mutant of diphtheria toxin,
was derived from bacterial fermentation. Being periplasmic, product was recovered from cell
extract. The cells were separated by either centrifugation. The protein was extracted from the
cells by chemical means like osmotic shock in sucrose. Extract containing product was then
processed through chromatographic purification step as follows.
Cibacron Blue pseudoaffinity Chromatography: Sorbent: Blue-sepharose
Buffers: Equilibration Buffer (15 mM Tris buffer pH 8)
Wash Buffer-I (5% IPA+0.05% Triton X-100+0.05 M NaCl, 15 mM Tris pH
8)
Wash Buffer-II (15 mM Tris buffer + 0.2 M NaCl, pH 8)
Elution buffer (15 mM Tris + 0.5 M NaCl, pH 8)
Regeneration Buffer (8 M Urea)
Cells obtained from 20 L fermentor were subjected to extraction by osmotic shock
using 30% Sucrose, 15 mM Tris pH 7.4, 5 mM EDTA and 50 mM Tris pH 7.4. The filtered
extract (45L) was loaded on Blue sepharose sorbent in 10 mM Tris buffer pH 8.0 and eluted
using 0.5 M NaCl in 10 mM Tris buffer pH 8. A column with 45 cm inner diameter (GE,
BPG 450/500) was packed according to the manufacturer instructions using 20 L Blue
Sepharose (GE) sorbent.
Column loading
The column was equilibrated with Equilibration Buffer (15 mM Tris buffer pH 8), for
about 1 CV until stable baselines for A2 o m and conductivity were obtained. The column was
then loaded with filtered extract containing sample at a flow rate of 240 L/h i.e. 150 cm h.
After loading, the column was washed again with about1 CV of equilibration buffer (15 mM
Tris buffer pH 8) to remove any residual material not tightly bound to the sorbent.
Column Wash I
The column was washed with 2 CV of Wash Buffer-I (5% IPA+0.05% Triton X-
100+0.05 M NaCl, pH 8.0) at a flow rate of 150 cm h until stable baselines for A28onm and
conductivity were obtained.to remove any protein, nucleic acid, lipid and lipopolysaccharide
impurities. The column was washed again with about 2 CV of equilibration buffer (15 mM
Tris buffer pH 8).
Column Wash II:
The column was washed with 2 CV of Wash buffer-II (15 mM Tris buffer + 0.2 M
NaCl, pH 8) at a flow rate of 150 cm/h until stable baselines for A2 o m and conductivity are
obtained.to further remove any protein and nucleic acid impurities.
Elution step
Protein product was eluted from the column with Elution Buffer (15 mM Tris + 0.5 M
NaCl, pH 8) at a flow rate of 150 cm/h in the form of a single A2 8o peak. Continue elution
until A
80nm
absorbance begins to decrease below 5 % of the peak value. About 2 column
volumes of Elution Buffer were necessary in this elution step. Column was regenerated by
passing 2 column volumes of 8 M Urea.
The method of purification involving Blue Sepharose column reduced the
lipopolysaccharide level to less than or equal to 500 EU/mg protein. Analysis showed that
nucleic acid, protein impurities, lipids and polysaccharides come out in the flow through and
various washes on Blue Sepharose sorbent. Resultant purified protein was highly pure with a
chromatography step involving washing steps of method of invention. A single step of
chromatography alone with washing steps of method of invention leads to more than 92%
purity with nucleic acid less than 0.1%.
Example 6: Polysaccharide purification with a mixed mode sorbent.
Neisseria meningiditis serotype B alpha 2-8 linked polysaccharide on a mixed mode
sorbent.
Equilibration buffer 10 mM sodium phosphate, 25 mM NaCl, pH 7.5
Wash Buffer-I 15% IPA+0.25% Triton X-100 + 0.1 M NaCl, pH 7.5
Wash buffer-II 6 M Urea+0.25% Triton X-100 + 0.1M NaCl, pH 7.5
Elution buffer 25 mM sodium acetate + 0.5 M NaCl, pH 5.0
A column packed with PPA HyperCel (Pall Life Sciences) is prepared according to the
manufacturer's instructions and equilibrated with equilibration buffer. A partially purified
extract of Neisseria meningiditis serotype B alpha 2-8 linked polysaccharide in buffer 1 is
loaded onto the column at 60 cm/hr. The column is washed with Equilibration buffer and
sequentially with Wash Buffers I and II, at 60 cm/hr. Each wash is continued until a stable
absorbance and refractive index baseline is achieved. The colominic acid is eluted with
Elution buffer.
Standard assays are performed to determine the concentration of colominic acid, host
cell protein, nucleic acid, lipid and nucleic acid. The product is substantially free of
contaminants.
Example 7: Purification of a basic protein on a cation ion exchanger.
Equilibration buffer: 50 mM sodium phosphate + 50 mM NaCl, pH 6.0
Wash buffer I 50 mM Na phosphate + 0.15 % Na sarcosine + 100 mM NaCl, pH 6.0
Wash buffer 1150 mM Na phosphate + 0.15% Na sarcosine + 150 mM Arginine, pH 6.0
Elution buffer 50 mM sodium phosphate + 500 mM NaCl, pH 6.0
A column is packed with CM Ceramic (Pall Life Sciences) according to the
manufacturer's instructions and equilibrated with equilibration buffer. Recombinant
lysostaphin from an E. coli supernatant is clarified, diluted into equilibration buffer and
filtered. The recombinant lysostaphin is loaded onto the column at 200 cm/hr and further
washed with equilibration buffer. The column is then washed sequentially with the two wash
buffers until the absorbance and refractive index returned to baseline. The product is then
eluted with the elution buffer.
Standard assays are performed to determine the concentration of protein, host cell
protein, nucleic acid, lipid and nucleic acid. Purity of the product is evaluated by SDS PAGE
and reverse phase HPLC. The specific activity of lysostaphin is determined by a
staphylococcus killing assay. The product is substantially free of contaminants.
Example 8: Purification of using a Q Sartobind ion exchange device.
Similar to examples 1 and 2 but using a Q Sartobind ion exchange device.
Example 9: Sartobind Phenyl membrane device.
Similar to example 3 but using a Sartobind Phenyl membrane device.
Example 10: ion exchange monolith device.
Similar to examples 1 and 2 but using an ion exchange monolith device.
Other embodiments and uses of the invention will be apparent to those skilled in the
art from consideration of the specification and practice of the invention disclosed herein. All
references cited herein, including all publications, U.S. and foreign patents and patent
applications, are specifically and entirely incorporated by reference. The term comprising,
where ever used, is intended to include the terms consisting and consisting essentially of.
Furthermore, the terms comprising, including, and containing are not intended to be limiting.
It is intended that the specification and examples be considered exemplary only with the true
scope and spirit of the invention indicated by the following claims.
Claims
1. A process for purification comprising:
contacting a mixture containing a target substance and one or more contaminants
to a chromatography matrix such that the target substance is bound to the
chromatography matrix;
washing the bound target substance with at least one wash buffer that contains a
combination of a lyotropic agent or an organic solvent, a detergent and a salt
component;
desorbing the bound target substance from the chromatography matrix with an
eluent; and
collecting the desorbed target substance wherein the concentration of the one or
more contaminants is reduced by 9 1 to 99.9%.
2. The process of claim 1, which is a single-step purification process.
3. The process of claim 1, wherein the target substance containing at least one or more
contaminants is a crude sample, a cell culture, a cell extract, a cell lysate, a
fermentation product, or a combination thereof.
4. The process of claim 1, wherein the target substance containing at least one or more
contaminants is derived from yeast, bacteria, or cell culture.
5. The process of claim 1, wherein the target substance comprises one or more of an
anionic polysaccharide, an anionic protein, a protein, a polysaccharide, an anionic
molecule, a cationic molecule, or a nucleic acid.
6. The process of claim 1, wherein the one or more contaminants comprises one or more
of media components, nucleic acids, endotoxins, proteins, lipids, or liposaccharides.
7. The process of claim 1, wherein the elate contains not more than 3 EU/mg of the at
least one or more contaminants.
8. The process of claim 1, wherein the elate contains not more than 2.5 EU/mg of the at
least one or more contaminants.
9. The process of claim 1, wherein the chromatography matrix is an anion exchange
chromatography sorbent, a cation exchange chromatography sorbent, a hydrophobic
interaction chromatography sorbent, a Cibacron Blue pseudo affinity sorbent, a mixed
mode chromatography sorbent, a membrane, a monolith chromatography device or a
combination thereof.
10. The process of claim 1, wherein the combination is synergetic and removes multiple
contaminants during the washing.
11. The process of claim 1, wherein the lyotropic agent is urea, guanidine hydrochloride,
arginine, sodium thiocyanide, or a combination thereof.
12. The process of claim 1, wherein the organic solvent is isopropanol, ethanol, glycerol,
ethylene glycol, propylene glycol, or a combination thereof.
13. The process of claim 1, wherein the detergent is Triton X-100, polysorbate 20,
polysorbate 80, sodium dodecyl sulfate (SDS), sodium sarcosine, or a combination
thereof.
14. The process of claim 1, wherein the salt is sodium chloride, potassium chloride,
ammonium sulfate, sodium phosphate, or a combination thereof.
15. The process of claim 1, wherein washing comprises washes with multiple wash
buffers, each wash of which is performed sequentially or independently.
16. The process of claim 1, wherein the at least one wash buffer contains about 2 to 30%
isopropanol, about 10 to 2000 mM of salt, and about 0.01% to 1% Triton X-100 at a
suitable pH.
17. The process of claim 16, wherein the suitable pH is from pH 5-9.
18. The process of claim 1, wherein washing comprises a second buffer containing about
1 to 8 molar urea, about 10 to 2000 mM of salt, and about 0.01 to 1% Triton X-100 at
a suitable pH.
19. The process of claim 18, wherein the suitable pH is from pH 5-9.
20. The process of claim 1, wherein washing comprises a third wash buffer that has a salt
concentration which is different than the concentration of salt in the eluent.
21. The process of claim 20, wherein the third wash buffer has a lower salt concentration
than the concentration of salt in the eluent.
22. The process of claim 1, wherein the concentration of the one or more contaminants in
the eluate is reduced by 99% or more as compared to the target substance before
purification.
23. A process for purification of a target comprising:
adsorbing a mixture containing the target and one or more contaminants to an ion
exchange chromatography matrix, wherein at least one of the one or more
contaminants comprises an endotoxin;
washing the bound target with one or more wash buffers wherein at least one wash
buffer contains a synergistic combination of a lyotropic agent or an organic solvent, a
detergent and a salt component;
desorbing the bound target from the chromatography matrix; and
collecting the desorbed target wherein the level of endotoxin is less than or equal
to 3 UE/mg of target.
24. The process of claim 23, wherein the amount of the one or more contaminants is in the
desorbed target is reduced by 91% to 99.9%.
25. The process of claim 23, wherein washing involves only a single wash buffer.
26. A purified target substance obtained by the purification process of claim 1.
27. The target of claim 26, which is a meningococcal C polysaccharide, Haemophilus
influenzae type b (Hib) polysaccharide, recombinant erythropoietin protein, or
recombinant CRM197.