Application Note

September 30, 2021
Keywords or phrases
Continuous processing, Ambr® 15 system, small scalebioreactor, DoE, mAb, perfusion mimicking, scale-down
model, process optimization

Transfer of Fed-Batch to Semi-Perfusion Process
Using Automated Small Scale Bioreactors
Sabrina Janoschek¹, Markus Schulze1, Gerben Zijlstra2, Gerhard Greller¹, Jens Matuszczyk¹¹ Sartorius Stedim Biotech GmbH, August-Spindler-Strasse 11, 37079 Goettingen, Germany² Sartorius Stedim Netherlands BV, Rotterdam, Netherlands
Correspondence
E-Mail: PBTsegment@sartorius.com

Abstract
Continuous processes offer advantages over batch approaches, including improved product quality, increased yield, and costsavings. This application note describes the use of the Ambr® 15 automated, high throughput microscale bioreactor systemwith perfusion mimic capabilities for transfer of a fed-batch process to perfusion using a semi-perfusion protocol. Cell culture
conditions, including medium and feed composition, glucose concentration, and the cell-speciﬁc perfusion rate, were exploredand optimized. The protocol was then transferred to an Ambr® 15 system and process performances were compared.
Using the same platform medium and proprietary feeds, a powerful but low resource approach to transfer an existing CHO
fed-batch process to a perfusion process using design of experiment (DoE) studies and perfusion-specific handling wasestablished. The suitability of the process for an Ambr® 15 system with perfusion mimic as scale-down model has been
demonstrated.
Application Note is excerpted from “A Protocol to Transfer a Fed-Batch Platform Process into Semi-Perfusion Mode:
The Beneﬁt of Automated Small-Scale Bioreactors Compared to Shake Flasks as Scale-Down Model,”published in Biotechnol. Prog. DOI 10.1002/btpr.2757 in August 2018.

For more information about Process Intensification, visit

www.sartorius.com/en/applications/biopharmaceutical-manufacturing/process-intensification

Introduction
The use of perfusion to improve efﬁciency of monoclonal
antibody (mAb) production is of great interest to thebiopharmaceutical industry. Perfusion-based processes canoffer advantages in terms of product yield, manufacturingcosts, and ﬂexibility compared to fed-batch processes.
Intensiﬁed processes are based on the continuous additionof fresh medium and removal of spent medium, which resultsin high cell concentrations and productivity in relatively smallbioreactors.
Clones selected under fed-batch conditions, however,may behave differently when transferred to a perfusion
process. To maintain the culture in a steady state, the cellspeciﬁc perfusion rate (CSPR) is one of the key processparameters that must be monitored and controlled. The
glucose concentration and the cell bleed rate are also essential.
In addition to these considerations, the process must be
successfully scaled–up, and critical process parameters,such as temperature, pH, or the oxygen transfer coefﬁcient,must be determined for process transfers.
Conventional bench-scale methods for development ofintensified processes are both time consuming and expensive
to execute. In addition, the cell retention step in a perfusion
process needs to be precisely and specifically adjusted
during process scale-up and automation. While alternatingtangential flow (ATF) or tangential flow filtration (TFF) are
widely used in the industry for cell retention, these approaches
are not available in the scale needed to be compatible withsmall volume (± 10 mL) high throughput microbioreactors
used for clone screening and the initial development of
perfusion processes. A more time- and cost-effective
approach uses a microscale bioreactor solution capable ofmimicking perfusion to enable fast track optimization ofmedia and culture conditions.

2This application note describes development and optimizationof a semi-perfusion protocol and transfer of the process fromclassical shake ﬂasks to an automated Ambr® 15 single-use,
microscale stirred tank bioreactor system with perfusion
mimic protocols.
As a first step, a standard medium formulation with proprietary
feeds used in fed-batch processes was adapted to thenutritional requirements of perfusion culture. Critical process
variables including CSPR, glucose concentration, and cell
bleed were investigated for the semi-perfusion operation.
The optimized semi-perfusion process in shake flasks wastransferred to the Ambr® 15 system, which also offeredadvantages for future testing of critical process parameters inearly development of continuous processes due to pH anddissolved oxygen (DO) control. The possibility of using theautomated small-scale bioreactor system as a screening
tool and scale-down model with increased process control
compared to shake ﬂasks was also evaluated. Ultimately, thiswork represents an easy perfusion-based protocol using theAmbr® 15 system to reduce costs and maximize the beneﬁts
of process intensiﬁcation.

Materials

Methods

Cell Lines and Medium

Semi-Perfusion Shake Flask Studies

A DG44 CHO cell line expressing an IgG1 mAb was used inthis study. Stock medium for the seed culture (SM) andproduction medium as basal medium for production (PM)were used as well as Feed Medium A (FMA) for macronutrients(e.g., glucose) and Feed Medium B (FMB) for micronutrients(e.g., amino acids). All medium and feeds used are chemicallydeﬁned.

Semi-perfusion 125 mL shake ﬂask cultures with a working
volume of 25 mL were inoculated from the seed train with astarting cell concentration of 2.5 million cells/mL. Eachmedium exchange took place in a 24-hour rhythm. For
sample analysis, shake ﬂasks were moved to the biologicalsafety cabinet, and 1 mL was removed after sufﬁcient shaking.
The remaining cell suspension was transferred into a 50 mL
Falcon tube by pipetting and centrifuged at 500 xg for fiveminutes at room temperature. Following centrifugation, 2 mLof the supernatant were taken for IgG quantiﬁcation, and theremainder was discarded by decanting. The cell pellet was
resuspended with 25 mL of pre-warmed, fresh medium bygentle pipetting, transferred into the shake ﬂask, and placedback into the incubator. To use the least amount of timepossible, the total duration of each centrifugation step did
not exceed a total time of 15 minutes.

Seed Culture
The shake ﬂask was incubated in an incubation shaker at
36.8 °C and 7.5% pCO2 with a shaking rate of 120 rpm and
85% humidity. Cells were passaged for ﬁve times every three
to four days until inoculation of the production culture was
done.

Design of Experiment Study
The experimental setup and the analysis of the results were
performed using MODDE® 12 design of experiment (DoE)software. A full factorial design was used to evaluate theinﬂuence of different medium compositions on the viable cellconcentration (VCC) as a single and quantitative responseusing a quadratic regression model, with FMA (three levels)and FMB (three levels) as the controllable and qualitative
mixture factors, and PM (nine levels) as the ﬁll factor(to 100%).

Cell Bleed in Semi-Perfusion Experiments
The cell bleed in shake ﬂasks was applied based on thedeﬁned conditions for each experiment and was calculated
based on the daily VCC and the total volume of the culture(Vc). The calculated volume of cell suspension was removed
by manual pipetting and replaced with fresh, pre-warmed
medium.

3

Parallel, Automated Small-Scale Bioreactor Analysis for IgG Quantiﬁcation
The automated small-scale bioreactor system Ambr® 15 withup to 48 disposable cell culture bioreactor vessels was usedin the experiments. Working volume of each bioreactor is
between 10 – 15 mL.
Each bioreactor was inoculated from the seed train with aseeding density of 2.5 million cells/mL. To achieve this higher
seeding density, cells from the seed train were centrifuged at
500 xg at room temperature for five minutes and resuspended
in pre-warmed medium for the semi-perfusion process.
The total duration of each centrifugation step did not exceed
a total of 15 minutes. Temperature set point was 36.8 °C andthe pH was 7.1. Agitation of each bioreactor was set to1,300 rpm and dissolved oxygen was controlled at 60%.
A constant N2 ﬂow was set to 150 μL/min to allow gas transfer.
The process lasted 12 days, with one vessel volume exchangeof medium per day (VVD) performed by spinning down thecells in the vessel and resuspending the cell pellet in 10 mL
fresh medium using the liquid handler of the Ambr® 15
system. Prior to each medium exchange, 2 mL of supernatantwere stored at −20°C for IgG quantiﬁcation. In addition,
supernatant was taken after the daily media exchange; thevolume varied to maintain the 10 mL working volume in eachbioreactor.

Ofﬂine Analytics
Process speciﬁc values for pH, glucose, lactate, and osmolality
were measured for every sample. With the VCC indicating
the quantity of viable cells in the cultivation, the viability andthe cell diameter were analyzed and the CSPR calculated.
The integral viable cell concentration (IVCC), also called
cumulative cell hours, indicates the total amount of time thecells have produced mAb and is calculated by trapezoidal
integration of the VCC over the time (t).

4

The cell-free supernatants of all samples were stored in thefreezer at −20 °C before IgG titer quantiﬁcation with HPLC
was performed. A mixture of 1 M Na2SO4, 0.5 M NaH2PO4+ 0.5 M Na2HPO4, and water (1 : 1 : 8) with a pH at 6.6 wasused as the buffer. Prior to analysis, samples were thawed
and diluted with water and ﬁltered through a 0.2 μm syringeﬁlters into autosampler cups using 1 mL syringes. The calibration
curve was measured based on an IgG stock solution.
To calculate the indicated cumulative product, measured
product concentrations were normalized to a volume of 1 L,
resulting in the product amounts. The product amount of thesupernatant after centrifugation, and the product amount of
the resuspended cells after the exchange of medium, werefactored into the calculation of the cumulative product,considering a 1 L working volume. By plotting the cumulative
product against the integral viable cells (IVC), the productivityof each process is indicated.

Calculation of Cell-Speciﬁc Productivity
and the Lactate Yield Coefﬁcient From
GlucoseThe cell-speciﬁc productivity (Qp) was calculated tocompare the key experiments from each bioreactor system,
the shake ﬂask and automated small-scale bioreactor, andthe newly established semi-perfusion process. The lactate
yield coefﬁcient from glucose was calculated based on
the speciﬁc glucose consumption and the speciﬁc lactate
production, with the glucose concentration, the lactate
concentration, and the geometric mean of the VCC.

Results and Discussion
DoE Studies for Medium Optimization
As a first step in this study, medium composition for thesemi-perfusion process was optimized. Different blends froma CHO fed-batch platform medium and its proprietary feeds
were investigated using DoE in shake flasks. FMA, FMB,
and the PM were combined in different blends to develop aformulation that would meet the requirements of higher cellconcentrations in the semi-perfusion process. The DoE wasbased on a full factorial central composite face-centered
design (CCF) containing the three factors PM, FMA, and FMB;
VCC was integrated as response factor. The experimental
design was based on an optimization response surface
methodology with a quadratic process model.

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Criteria for optimization were VCC and viability of the cell
population (Figure 1A). VCCs up to 45 million cells/mL wereobtained, which is twice the number of cells compared tothe previous fed-batch process. With the medium blends
PF1_DoE4 and PF1_DoE8, viability and VCC were high overa period of 250 hours. In all other shake ﬂasks, the viability
decreased dramatically after 170 hours. These results indicatethat addition of both feeds and 8% FMA is necessary for astable process.

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Cumulative product [g]70

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IVC [109 c×d]

Figure 1: Results of DoE for semi-perfusion medium optimization with a mAb producing DG44 CHO cell line. The VCC and viability (A), the glucose concentration
and CSPR (B), and the product yield of the antibody in relation to the IVC (C) of each shake ﬂask run are shown. Center point PF1_DoE9 based on n = 3.
5

However, the increase of the FMA concentration was limited
due to higher osmolality with increasing nutrient concentration.
The glucose proﬁle (Figure 1B) showed a lack of glucose
for nearly every cultivation after 150 hours; lack of glucose
corresponded with a strong decrease in viability and VCC.
The correlation of the glucose concentration and thedecreased viability and VCC indicated a possible glucose
limitation during the cell cycle and other metabolic processes
and requires further optimization.

The DoE response surface plot showed that with 8% FMA,
a local optimum was reached (Figure 2). However, further
increases of FMA and FMB to optimize the ﬁrst screening DoE
is likely to result in an osmolality exceeding 400 mOsmol/kg,
which may reduce CHO production rates. The resulting local
optimum was used as a satisfactory compromise between
performance and osmolality.

The CSPR values (Figure 1B) indicated a lower limit at
50 pL/(c × day). The cumulative product represented the
product concentrations before and immediately after
centrifugation based on the integral of viable cells in the cell
culture. Product yield of the antibody in relation to the IVC ofeach shake ﬂask run is shown in Figure 1C. The cumulative
product in the semi-perfusion processes showed a clear
improvement up to 12 g compared to the normal fed-batchprocess with an average of 3 g in the corresponding working
volume of 1 L.
VCC [106 cells/mL]
0.007

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Figure 2: Response surface plot of DoE. The evaluation is based on VCC and different feed fractions (%) in the medium blends. The response of the target
variable is color coded, ranging from blue (low) to red (high).
6

Optimization of Glucose Concentrations
One critical factor during process transfer from fed-batchmode to perfusion processes was the glucose concentration.
As can be seen from the DoE study, it was necessary to
optimize the amount of glucose in accordance with thehigher cell concentrations obtained in the semi-perfusion
process.

of the correlation between each component. In a second
step, glucose spikes were added directly to the culture after
the daily medium exchange (Figure 3).

Different compositions of PM, FMA, and FMB together withglucose (added directly to the compositions) were analyzed.
These compositions were tested to gain a better understanding

Both experiments showed similar culture behavior, achieving
a longer stability and the favored 12 days of cultivation withhigh cumulative products. The control composition PF2_Glc1,
without any additional glucose, showed the same glucose
depletion after ﬁve cultivation days as in previous experiments.
Best results in viability were achieved in PF2_Glc4, PF2_Glc5,

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Cumulative product [g]70PF3_GlcSpike2

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IVC [109 c×d]
Figure 3: Performance of shake ﬂasks with implementation of additional glucose spikes in the semi-perfusion processes of a mAb producing DG44 CHO cell line.
For PF3_GlcSpike1 glucose was spiked with 4 g/L daily after Day 5 of cultivation. The medium composition for PF3_GlcSpike1 was 91.2% PM, 8% FMA, and 0.8%
FMB. The glucose spike for PF3_GlcSpike2 was applied daily starting from Day 1 if the subtraction of the glucose consumption of the last 24 h from the actual
glucose concentration was below 2 g/L. In that case, a spike of 4 g/L was carried out. The medium composition for PF3_GlcSpike2 was 100% PM in the ﬁrst threedays and 91.2% PM, 8% FMA, and 0.8% FMB in the following days. The VCC and viability (A), the glucose concentration and CSPR (B), and the product yield of
the produced antibody in relation to the IVC (C) of each shake ﬂask run are shown. Depicted are the mean values of duplicate measurements (n = 2).
7and PF3_GlcSpike1, which contained 91.2% PM, 8% FMA,
and 0.8% FMB. This medium composition was used in thefollowing experiments and is referred to as the semi-perfusion
medium.
Addition of glucose was highly beneﬁcial for stability of thesemi-perfusion process with VCCs up to 40 million cells/mL.
At a CSPR of 50 pL/(c × day), a decrease in viability could beseen in the following days. Glucose additions starting from
2 g/L to 8 g/L were beneﬁcial for higher CSPR values.
No difference was observed between the two approaches toadding glucose to the cell culture; as such, the glucose spike
was further evaluated, as it offers advantages in easier
handling and better adaption to batch-to-batch variations incell growth. However, viability in both experimental setups
decreased to 60% on the last two cultivation days. As viabilities
below 70% are common harvest criteria, further improvementof the process stability and higher CSPR values are desirable.

Inﬂuence of the Cell Bleed on
Cell Culture Stability
In order to move from a fed-batch culture to perfusion, a cell
bleed was essential to maintain a stable VCC over prolonged
process time, provided that the VVD of 1 is kept constant.
In this study, different cell bleed strategies were tested
instead of increasing the VVD. In addition, to further improveglucose concentrations and the correlation of cell bleed andglucose spikes, different combinations of bleed and glucose
additions were evaluated. The cell bleed was combined withthe daily media exchange.
In all approaches applying the cell bleed to the semi-perfusion
shake ﬂask cultures, peak VCCs of 25 million cells/mL or
higher were achieved (Figure 4A). However, the ﬁrst bleed
condition (PF4_Bleed1 with a bleed VCC of 40 million cells/mL
and a high glucose addition to 4 g/L from Day 5 on) showeda decrease in viability to 65% on the last cultivation day. Thisviability was lower than the desired viability of 70% at the endof the semi-perfusion culture. Therefore, the high bleed VCC
is not beneﬁcial for a stable semi-perfusion process with thegiven VVD of 1. Moreover, the VCC of PF4_Bleed1 was similar
to the VCC achieved in PF4_Bleed4 with a bleed threshold of
25 million cells/mL. In both approaches, the CSPR fell below
50 pL/(c × day) after 110 hours of cultivation, resulting in adecrease of viability and inhibition of further cell growth tohigher VCCs. These results indicate that the bleed should beapplied at an earlier stage with lower target bleed VCCs.
8

Higher VVDs might support stable cell populations withhigher VCCs without the need to bleed; however, thissignificantly increases medium consumption and costs.
Every bleed condition with a target bleed concentrationof 20 million cells/mL (PF4_Bleed2 and PF4_Bleed3) or
25 million cells/mL (PF4_Bleed4) showed viabilities above
70% on the last day of cultivation with similar peak VCCs ofapproximately 30 million cells/mL. In addition, the glucose
concentration was not limited in the semi-perfusion medium
over the complete process time (Figure 4B). Interestingly,
PF4_Bleed2, with no additional glucose spiking, showed no
glucose limitation and was characterized by the highest
viability (> 80%). This indicates that the bleed in a semi-perfusion
process enables constant CSPR values above the critical
CSPR and is fundamental for culture stability.
Furthermore, the highlighted condition was constantly
bled to the smallest investigated bleed level of 20 million
cells/mL. According to previous observations, the decreaseof CSPR below 50 pL/(c × day) in each shake ﬂask run wasaligned with a lower viability in the following culture days.
Cumulative product was increased signiﬁcantly to 10 g incomparison to the fed-batch process (Figure 4C).
Medium optimization and corresponding cell bleed adaptation
led to successful semi-perfusion cultures with ﬁnal viabilities
of more than 70% after 12 days of cultivation. Based on theseﬁndings, the medium formulation was defined as 91.2% PM,
8% FMA, and 0.8% FMB with a target bleed concentrationof 20 million cells/mL.
The following experiments demonstrate how this semiperfusion process can be transferred into an automatedsmall-scale bioreactor system. This enables more processcontrol and facilitates future investigations of the new process.
Due to the direct transfer of the optimized process into
the small-scale bioreactor, the advantage of the automatedbioreactor as scale-down model for process optimization
over the classical shake ﬂask approach was investigated.

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IVC [109 c×d]
Figure 4: Implementation of cell bleed in the semi-perfusion processes of a mAb producing DG44 CHO cell line. The VCC and viability (A), the glucose
concentration and CSPR (B), and the product yield of the antibody in relation to the IVC (C) of each shake ﬂask run are shown. Depicted are the meanvalues of duplicate measurements (n = 2).

Use of Automated Small-Scale
Bioreactor System to Control pH and DO
Following conversion of the fed-batch process to a semiperfusion process in shake ﬂasks, the process was transferred
to an automated small-scale bioreactor system. This transfer
enabled greater process control of relevant process parameters(e.g., DO, pH), enabled better process understanding throughmonitoring of key performance indicators, and offered thepossibility to establish automated medium exchanges.

Due to improved process control of the parameter set points,
and especially the pH control at 7.1 in the automated bioreactor,
higher cell growth rates were expected. Therefore, additional
glucose was spiked (2 g/L to each bioreactor) whenever the
resulting glucose concentration for the following day wascalculated to be below 2 g/L based on the speciﬁc glucose
consumption per cell. The glucose spike was implemented tomaintain a stable culture over the total cultivation time.

9

Figure 5 shows the results of the process transfer to theautomated system. For all critical parameters, the favored
criteria were achieved. The culture was stable over the entire
culture time of 12 days. A concentration of 20 – 30 million
cells/mL was achieved and kept as steady-state concentration
with the help of precise cell bleeds (Figure 5A).
Viability exceeded 98% for half of the cultivation time anddecreased to 95% once the previous detected critical CSPR
of 50 pL/(c × day) (Figure 5B) was reached. Therefore, it was
shown that maintaining CSPR above 50 pL/(c × day) resulted
in a stable cell culture with high viabilities.

In the bioreactor system, cell viability was signiﬁcantly higher than in any other shake ﬂask experiment; additionally, theprocess was more stable than in uncontrolled shake ﬂasks.
The process was controlled to the pH set point of 7.1 andthe DO set point of 60% over the complete culture time
(Figure 5D). Comparing the pH values to the shake ﬂask
experiments showed a marked improvement of control.

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In addition, an oscillation of DO could be detected in theautomated bioreactors over the cultivation period; this wasa result of high cell densities creating an increased oxygen
demand that triggered a more active control loop andsubsequent oscillations in the DO signal.

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Time [h]Figure 5: Transfer of the semi-perfusion processes of a mAb producing DG44 CHO cell line to an automated small-scale bioreactor system. The VCC andviability (A), the glucose concentration and CSPR (B), and the product yield of the antibody in relation to the IVC (C) are shown. Error bars are reported
for each value. The controlled parameters, the pH value and the DO of the process, are shown here (D). Mean values of triplicate measurements (n = 3)
are depicted.
10Based on the generated data for DO and pH control,
experienced users will develop a sound understanding ofprocess behavior at larger scales. Therefore, the use of smallscale bioreactors is highly favored to gain deep knowledge
for intensiﬁed bioprocesses. However, in a large-scalebioreactor, the process will be implemented as a fully
continuous process with a suitable cell retention device.
The change from centrifugation in small-scale bioreactors tocell retention in large-scale bioreactors will enable culture
control and process monitoring over the complete process
time.
Application of glucose spikes whenever the glucose
concentration was below the threshold of 2 g/L led to a
sufﬁcient nutrient supply for the semi-perfusion cell culture.
The cumulative product of 8.7 g in the semi-perfusion
process was three-fold higher than in the corresponding
fed-batch process. The resulting standard deviations showed
the three bioreactors performed consistently throughout theprocess. The product amount over the total culture time canbe further improved by cultivating the semi-perfusion culturein the controlled system for longer periods in the future.
The possibility of longer cultivations was enabled by thehigher stability and high viability in the controlled bioreactors.
Due to the consistent and controlled semi-perfusion process
in the small-scale bioreactors, conclusions can be comparedand used to improve process understanding for continuous
processes and implementation of perfusion in suitablebioreactors with cell retention devices. Furthermore, theresults can be used to predict and optimize the scale-up to
production scales.
Finally, the fed-batch process, the successful implementationof semi-perfusion processes in shake ﬂasks, and the processtransfer in the automated small-scale bioreactor can becompared. This comparison can be based on the lactate
production compared to glucose consumption (YLac/Glc),
the speciﬁc productivity, the increase in cell diameter, thecumulative product as well as the IVC, and the end viabilityof each process.

YLac/Glc allows deeper information about the cell state
and the metabolism in the cells. Glucose is used in different
pathways based on the metabolic state and the nutrients inthe environment, while lactate is a waste product in unfavorable
pathways that can inhibit the cell growth. Therefore, a low
YLac/Glc indicates efﬁcient cell metabolism with low lactate
production or lactate consumption by the cells. In the beginningof each process, YLac/Glc is signiﬁcantly lower in the semiperfusion process, indicating a more efﬁcient metabolism
than in the corresponding fed-batch cultivation. The biggest
positive effect was achieved in the automated small-scalebioreactor with values around 0; the ratio of glucose
consumption and lactate production indicated a highly
productive and healthy cell culture. These ﬁndings were
supported by the lactate production over time in each of thethree cultures. At the start of the original historic fed-batch, asigniﬁcantly higher lactate production was detected before
the cells switched into lactate consumption. Furthermore,
the increase in cell diameter (indicating apoptotic cells)
was much less for the established semi-perfusion processcompared to the historic fed-batch, indicating a more viable
cell culture. Another beneﬁt of the semi-perfusion process
is the low osmolality (~310 mOsmol/kg at the end of theprocess in comparison to ~360 mOsmol/kg in the fed-batch).
The higher osmolality can support the increase in cell diameterin the fed-batch.
Finally, the average speciﬁc productivity was increased
to a ﬁnal productivity of 38.88 pg/(c × day) in the automatedsmall-scale bioreactor. The cumulative product and the IVC
increased signiﬁcantly in the semi-perfusion processes
during the same culture period compared to the fed-batch.
The automated small-scale bioreactor performed better
regarding the end viability of 95.23% compared to the semiperfusion in shake ﬂask or the fed-batch process. These
results indicated that the Ambr® 15 platform performed bestin the studies in terms of product yield and viability of the cell
culture. The beneﬁt of the automated small-scale bioreactor
as scale-down model was clearly shown compared to theshake ﬂasks.

11

Conclusion
The ability to mimic perfusion during cell line screening andinitial process development is essential to identify suitableclones, as well as key parameters, and to optimize culture
conditions for process intensification. The strategy describedin this application note utilized the Ambr® 15 automated,high throughput microscale bioreactor system to transfer
an existing CHO fed-batch process into a semi-perfusion
process leveraging DoE studies. In addition, suitability ofthe process for a multi-parallel controlled microbioreactor
system as scale-down model has been demonstrated,indicating that early stage development of a semi-perfusion
process can be done in a controlled system.

Germany
Sartorius Stedim Biotech GmbH
August-Spindler-Strasse 1137079 Goettingen
Phone +49 551 308 0

In this study, conversion of a fed-batch process to semiperfusion was successfully demonstrated by using the same
platform medium and its proprietary feeds. The product yield,
normalized to 1 L of the corresponding fed-batch process,increased from 3 g to a cumulated product amount of 10 g in
the semi-perfusion process for the same cultivation duration.

USA
Sartorius Stedim North America Inc.
565 Johnson Avenue
Bohemia, NY 11716
Toll-Free +1 800 368 7178

F or more information, visit
www.sartorius.com

Specifications subject to change without notice.
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Status: 09 | 30 | 2021