1. December 2015 13(11)si BioProcess International A
GE Healthcare
Comparing single-use and stainless steel
strategies for microbial fermentation
Ken Clapp, Eva Lindskog, Kjell Eriksson, and Sandeep Kristiansson
Process economy and
production capacity
2. B BioProcess International 13(11)si December 2015
Figure 1: Production schedules for a single-product facility using either (a) stainless steel or (b) single-use equipment; in the
former, one complete culture (including equipment preparation) takes four working days to complete. With single-use
equipment, the culture can be harvested after only three days, saving a full working day.
0Preparations
Weighingofmediacomponentsandadditive
Handlingofdisposablesandchemicalsatwarehouse
MixmediaasaconcentratefortheSSfermentor
Mixandautoclave/filteradditives
Assembleandautoclavefermentortubings
Production
Preparationsinfermentorroom
Pressureholdtestoffermentor
Calibratefermentorsensors,connecttubing
Connectandaddmedia,WFI,additivestofermentor
SIPoffermentor(includingmediaandsensors)
Inoculation
Additionofnonautoclavableadditives
FermentationFirstbatchSecondbatch
Heattreatmentforproductreleaseandharvest
CIP
Wastedisposal
246810121416182022024681012141618202202468101214161820220246810121416182022
BatchDuration
MondayTuesdayWednesdayThursday
0Preparations
Weighingofmediacomponentsandadditive
Handlingofdisposablesandchemicalsatwarehouse
Mixmedia
Mixandautoclave/filteradditives
Assembleandautoclavefermentortubings
Calibrateandsterilizesensorstofermentor
Production
Sensorandtubinginstallationandconnection
Preparationsinfermentorroom
Transferandfiltermediaandadditives
Inoculation
Heattreatmentforproductreleaseandharvest
Fermentationproductionprocess
Wastedisposal
FirstbatchSecondbatch
BatchDuration
Thirdbatch
246810121416182022024681012141618202202468101214161820220246810121416182022
MondayTuesdayWednesdayThursday
(A)
(B)
3. December 2015 13(11)si BioProcess International 1
S
ingle-use technology spans a vast array of
applications and associated products.
Single-use components have been
incorporated into subsystems and overall
systems alike. Disposable filters, fittings,
connectors, and tubing (among other things) have
been a mainstay of bioprocess operations for
decades. Proper application, selection, and
implementation of disposables have been essential
to improving biopharmaceutical end-product
quality, reducing cost, and simplifying operations.
In recent years, single-use technology has been
migrating into many unit operations. Of interest for
this discussion are fermentors for microbial culture.
Like some components mentioned above, single-use
bioreactors have been implemented for over a decade.
Practical implementation, commercial availability,
and lack of scalability were early limitations to
adoption and use of such systems. That was until the
WAVE Bioreactor system burst onto the market,
sowing the seed for growth of single-use bioreactors
and fermentors across the market.
With the commercial availability of such
systems, end users had a new option for process
development and production that would not rely
on operational complexities and utility
requirements of conventional sterilize-in-place
(SIP) or autoclavable systems. The resulting
freedom allowed for revisiting old ways of working
and the opportunity to consider new ways to think
about bioprocessing, including a focus on cost
structures prevalent in the industry.
At first, the idea of a “plastic bag” bioreactor
was met with some skepticism. However, benefits
came with appropriate application and proper
implementation of the technology. Success with
the rocking platform made way for single-use
stirred-tank bioreactors to emerge. They could rely
on decades of design and performance experience
established by their stainless steel counterparts.
Despite all that experience, here too the
technology was adopted cautiously. But single-use
bioreactors have found their place and become a
foundation of bioproduction based on animal
(particularly mammalian) cell culture.
Success with single-use systems in large-scale cell
culture — along with advances in material science,
improvements in design understanding, and a
resurgence of microbe-based biologics production —
are converging to create exceptional opportunities.
Whereas for animal cell culture, little was known
initially about single-use bioreactor scalability and
long-term viability, the same is not true for single-
use fermentors and microbial
culture. Cell culture in single-use
bioreactors has created a body of
knowledge related to process
equipment, single-use bag assemblies,
and their integrated operability. That
body of knowledge can serve as a
springboard for microbial applications and
should lower their threshold for adoption.
It is important to note, however, that just as for
cell culture processes, single-use technology may
not apply to each and every microbial process. It is
the responsibility of practitioners to properly assess
their own applications, select appropriate
technology, and manage its implementation.
Adopting a technology just for the sake of doing
so can prevent consideration of important variables
and may not lead to successful outcomes. The
motivation to incorporate a single-use fermentor
into a development or production environment
must be based on an understanding of the value it
brings to a given company and product.
Implementing single-use technology also means
accepting change, challenging conventional
thinking, and reconsidering established ways of
working. With all this in mind, GE Healthcare
presents the following process-economic model as
a contribution to discussions about implementing
single-use fermentors.
Process-Economic Comparison
GE Healthcare has compared production capacity
and process economy between stainless steel and
single-use equipment in microbial processes.
Economic simulations are based on an Escherichia
coli domain antibody (DAb) process, with
production scenarios considered for both single-
and multiproduct facilities.
This study shows that annual production
capacity can be increased up to 100% over
stainless steel with a single-use strategy, primarily
because of faster batch change-over procedures.
With that increased production capacity, a defined
number of batches can be produced in a shorter
time using disposables (e.g., in a manufacturing
campaign or during process development).
Increased batch throughput presents a greater
profit opportunity, a benefit that can outweigh the
higher production cost per batch associated with
the single-use alternative. With the decreased
financial risk, the business case for single-use
equipment becomes more agile than for stainless
steel equipment that incurs higher fixed costs.
special
report
4. 2 BioProcess International 13(11)si December 2015
Background: Microbial fermentation is used for
manufacturing a broad range of products in the
biopharmaceutical industry, including small
nonglycosylated proteins such as human growth
hormone, peptides such as insulin, organic
molecules such as antibiotics, and vaccines against
pneumonia and cholera. Recently, biosimilars,
biobetters, and antibody fragments have been
added to the list of products produced by
fermentation processes.
The primary advantages of microbial
fermentation include straightforward cloning
procedures, simple culture conditions, and rapid
culture growth. By comparison with eukaryotic
cells, microorganisms are less complex and limited
in, for example, their ability to perform
posttranslational modifications. Extensive research
has been conducted to enhance microbial
expression systems, including glycoengineering to
enable correct protein glycosylation capability. The
dominant organisms in today’s biomanufacturing
are E. coli and Pseudomonas fluorescens bacteria,
Saccharomyces cerevisiae and Pichia pastoris yeasts,
and Aspergillus filamentous fungi.
Historically, bioreactors and fermentors have
been constructed of stainless steel or glass. At the
end of the 1990s, however, plastics entered the
scene, providing for the possibility of using
disposables and single-use equipment in culture
processes. Adoption of early single-use rocking
WAVE Bioreactor systems showed that users could
save both time and money through this novel
disposable approach. Soon, Xcellerex bioreactors
(with their bottom magnetic drive) pioneered the
single-use stirred tank field, enabling use of
disposables from small-scale process development to
2,000-L manufacturing scale. Although both
rocking and stirred-tank systems were designed for
mammalian cell culture, they also have found use in
some microbial processes with lower optical density
(OD) requirements.
Microbial biomanufacturers are also interested in
the benefits of single-use bioreactors: increased
process flexibility, reduced cross-contamination
risk, and higher batch throughput. However, the
associated engineering requirements are more
challenging for fermentors used in microbial
processes than for bioreactors used in animal cell
culture. Sufficient mass transfer of oxygen and
removal of excess metabolic heat are some specific
requirements of a microbial process. The Xcellerex
XDR-50 MO system was the first single-use
stirred-tank fermentor purpose-designed for
microbial cultivation. A 50-L fermentor system was
introduced in 2007 and is currently used in both
process development and good manufacturing
practice (GMP)–compliant production of
recombinant proteins and vaccines. The XDR-50
MO fermentor exhibits performance comparable
with stainless steel systems, accommodating an OD
as high as 375 in a P. fluorescens culture producing a
monoclonal antibody (1). Success with the 50-L
fermentor led to the announcement of a larger
500-L XDR-500 MO fermentor in 2015.
What remains to be understood are the
process-economic implications of using disposables
for microbial biomanufacturing: to identify
scenarios in which single-use solutions can be
more favorable than traditional stainless steel
equipment. Here, such questions are discussed
Table 1: Capital investment costs
Stainless Steel System Single-Use System
Biostat D-DCU 50-L single O2
enrichment bioreactor with
control unit
Xcellerex XDR-50 MO
fermentor system
Bioreactor vessel load cells Exhaust condenser for
XDR-50 MO
System clean-in-place (CIP) and
steam-in-place (SIP) operations
Temperature control
unit (TCU) for XDR-50
MO
Extended documentation Xcellerex XDM Quad
single-use mixing
system
Substrate pump
Pressure hold test
Table 2: Unit operations for qualification and cleaning
validation (NA = not applicable)
Unit Operation
Stainless
Steel
Single-
Use
IQ/OQ of fermentor and control
unit (establishing of protocols)
Included Included
IQ/OQ of fermentor and control
unit: factory acceptance test
(FAT) and site acceptance test
(SAT)
Included Included
IQ/OQ of fermentor and control
unit (reporting)
Included Included
OQ temperature mapping of SIP
procedure
Included NA
PQ of fermentor (using
bioindicators for stainless steel
system) and control unit
Included Included
Cleaning validation Included NA
Sterile medium hold test Included NA
IQ/OQ of mixing unit
(establishing of protocols)
NA Included
IQ/OQ of mixing unit (FAT and
SAT)
NA Included
IQ/OQ of mixing unit (reporting) NA Included
Analytics for cleaning validation
and sterile medium hold test
Included NA
5. December 2015 13(11)si BioProcess International 3
based on a model setup for an E. coli DAb
production process run at 50-L scale (2). Data and
assumptions were validated; that is, prices and
costs were verified to generate a nonbiased and
realistic outcome that should facilitate decisions
related to microbial production scenarios.
Process-Economic Model: A model E. coli DAb
process was used to assess process economy in four
hypothetical production scenarios involving both
single-use and stainless steel equipment in single-
product and multiproduct facilities: single-product
facilities with stainless steel and single-use
equipment, and multiproduct facilities with
stainless steel and single-use equipment.
The scope of this process-economic simulation
is limited to the upstream fermentation process
and DAb production phase.
Other unit operations (e.g.,
downstream processing) have
been omitted for simplicity. The
single-use fermentor unit selected
for this investigation was the
Xcellerex XDR-50 MO system, and a
Biostat D-DCU 50-L stainless steel
fermentor (Sartorius Stedim Biotech) was used as
a reference. Specific objectives for this
investigation include the following:
• Investigation of equipment-choice effects on
production capacity
• Estimation of batch-production costs for
processes in which either stainless steel or single-
use equipment was used
special
report
Figure 2: Production schedules for a multiproduct facility using either (a) stainless steel or (b) single-use equipment; the time
dedicated to maintenance (red) is equal in both scenarios, whereas the time dedicated to cleaning and associated analyses (yellow)
is shortened with single-use equipment. The time needed for carry-over calculations, reporting, and quality assurance (QA) approval
(blue), included in the stainless steel scenario is omitted from the single-use scenario. If five batches are harvested (green) in each
campaign, then 67 batches can be harvested annually with stainless steel and 135 annual batches with single-use equipment.
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
31
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
31
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
31
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
31
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
31
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
31
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
31
January February March April
May June July August
September October November December
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
31
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
31
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
31
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
31
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
31
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
31
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
31
January February March April
May June July August
September October November December
(A)
(B)
6. 4 BioProcess International 13(11)si December 2015
• Understanding of how equipment strategy
affects total annual cost at different batch
throughputs
• Assessment of profit opportunity for different
equipment strategies.
General Assumptions: Several general
assumptions were made. Availability for
fermentation was set at 300 days/year; the remaining
time would be dedicated to annual maintenance.
Capital investments (including 10% interest) and
qualification costs are spread over the number of
batches that can be produced during the equipment’s
depreciation period (10 years). Labor costs are set at
US$100/hour. Fermentation is assumed to run
overnight, with two operators present to monitor the
process (same for all scenarios). Labor is divided into
two shifts: 6:00 am to 2:00 pm and 2:00–10:00 pm.
And no batch failure rate was considered.
The aim of this study was to make an objective
comparison between single-use and stainless steel
fermentors to provide a representative assessment
of the two alternatives and aid in understanding
their respective strengths and weaknesses. Hence,
all assumptions and costs were verified with data
or information from existing processes whenever
possible. The following specific assumptions were
made:
• For single-product facilities (scenarios 1 and
2, single-use and multise, respectively), only one
product would be produced and the 300-day
production capacity used to 100%.
• For multiproduct facilities (scenarios 3 and 4,
single-use and multiuse, respectively), the facility
would produce different products and use its 300-day
production capacity to 100%. Products were assumed
to be produced in five-batch campaigns each.
Cost Categories: The model includes five cost
categories: capital investments (Table 1);
installation and operation qualifications (IQ/OQ ),
performance qualification (PQ ), and cleaning
validation (Table 2); annual requalification and
maintenance (Table 3); process-related costs (Table
4); and disposables, chemicals, water for injection
(WFI), steam, and similar necessities (Table 5).
The process-related costs listed in Table 4 includes
system preparations before fermentation and the
fermentation process itself. Costs of qualifications,
cleaning validation, annual requalification, and
maintenance (as well as production-related costs)
were estimated by evaluating the labor in hours
required for each respective unit operation.
Some elements were omitted from the model
because certain needs and procedures are identical
for all scenarios or have minimal differential cost
effects. Those with identical needs include a seed-
culture generation procedure using shaker flasks;
the type and amount of culture medium
components and supplements; minor hardware
such as scales and tube welders; minor disposables
(e.g., C-Flex tubing, pump tubing, syringe filters,
vials, and so on); the number of autoclave cycles
for tubing sterilization (cost for steam and
electricity); nitrogen for calibration of dissolved
oxygen (DO) sensors; and general facility
requirements. Elements with minimal impact on
overall cost include energy consumption per batch
and air and oxygen demands (which are slightly
higher for single-use equipment because of its
lower maximum stirring speed). The model
excludes a cost of goods sold (CoGS) calculation
for given amounts of final product because of the
small production volumes assumed.
Results
Production Capacity: Production schedules were
developed for stainless steel and single-use
fermentation scenarios in a single-product facility.
Stainless steel fermentation batches can be
harvested every third day, allowing for a
maximum of 100 batches per year at 100%
capacity use with the assumption of 300 available
days. Under the same conditions, single-use
Figure 3: Production capacity for the four scenarios included
in this study
0
Single-Product
Facility
NumberofBatchesAnnually
Multiproduct
Facility
Stainless steel
Single-use
20
40
60
80
100
120
140
160
Table 3: Unit operations for annual requalification and
maintenance (NA = not applicable)
Unit Operation Stainless Steel Single-Use
OQ temperature
mapping of SIP
procedure (annual
retesting)
Included NA
Cleaning validation
(annual recovery study)
Included NA
Annual maintenance of
fermentor system
Included Included
7. December 2015 13(11)si BioProcess International 5
fermentation batches could be harvested every
second day, allowing for a maximum of 150
batches per year.
For the production scenario in Figure 1, a batch
produced in single-use fermentation equipment will
take 33% less time to complete than one made in
stainless steel. Figure 2 outlines production
schedules for both scenarios in a multiproduct
facility. The stainless steel equipment supports
production of 67 batches/year, about 13 full
production campaigns annually. The corresponding
numbers for single-use equipment is 135 batches/
year in 27 full campaigns. For this multiproduct
facility, production capacity can be doubled with
single-use equipment over stainless steel.
Figure 3 summarizes production capacities for
all four scenarios. Throughput is higher in the
single-product facility than in the multiproduct
facility. And in both, single-use equipment enables
a higher throughput than does stainless steel.
However, the difference between single-use and
stainless steel equipment is most prominent in the
multiproduct-facility scenario.
Cost Analyses and Profit Opportunities
Cost/Batch: The total cost per batch was calculated
for all four scenarios, and detailed analysis was
based on assessing costs for six main categories:
capital investments, qualification, annual
maintenance and requalification, production
preparations, production (fermentation), and
consumables (disposables, facility media, and
chemicals). The costs for a batch production in
stainless steel scenarios served as a reference when
normalized and set to 1.00 for all categories.
Figure 4 summarizes the results.
Total cost and individual cost profiles are very
similar for both facility scenarios. Relative to
stainless steel processes, the total cost per batch is
higher for single-use processes: 29% higher in a
single-product facility and 25% higher in a
multiproduct facility. The higher batch cost with
single-use equipment comes from an increased
consumables cost. For stainless steel, however,
capital investments, qualification costs, and annual
maintenance costs are all higher. That can be
expected because a facility based on stainless steel
reusable equipment requires more fixed
infrastructure. Production-related costs are
comparable for all scenarios.
Costs for Varying Facility Use Rates: Batch cost
analysis was based on the assumption that each
facility’s production capacity is fully used. In
reality, however, many facilities
run at lower use rates, which
changes the dynamics of this
cost-calculation model. In certain
cases (e.g., during a manufacturing
start-up scenario), use rate might be
very low. If only four batches are
required for toxicology studies during the
first year and an additional 15 batches for phase 1
studies during the second year, for example, a
company would still need to invest in the
equipment early on. So equipment qualification
special
report
Table 4: Unit operations for production activities (NA = not
applicable)
Unit Operation
Stainless
Steel
Single-
Use
Handling of disposables and
chemicals
Included Included
Weighing of medium
components and additives
Included Included
Mixing of medium and additives Included Included
Autoclave/filter additives Included Included
Assemble fermentor tubing Included Included
Autoclave fermentor tubing Included Included
Connect tubing to fermentor Included Included
Connect medium and additives
to fermentor tubing
Included Included
Preparations in fermentation
room
Included Included
Calibration of fermentor sensors Included Included
Sterilization of sensors NA Included
Installation of single-use
fermentor bag and sensors
NA Included
CIP of fermentor Included NA
Pressure hold test of fermentor Included NA
Transfer medium concentrate
(including autoclavable
additives) and WFI to stainless
steel system
Included NA
SIP of fermentor including
sensors
Included NA
Filtration of additives (non-
autoclavable) into stainless steel
system
Included NA
Transfer medium to single-use
fermentor bag via filtration
NA Included
Transfer additives to single-use
fermentor bag
NA Included
Inoculation of bacterial cell
culture
Included Included
Fermentation Included Included
Heat treatment before harvest Included Included
CIP of fermentor Included NA
SIP of fermentor Included NA
Waste disposal Included Included
8. 6 BioProcess International 13(11)si December 2015
and costs for annual maintenance and
requalification also would need to be considered.
To investigate this further, analysts used four,
15, 30, 50, 100, and 150 annual batches as input
data for the model and calculated the annual costs
for stainless steel and single-use scenarios,
respectively (Figure 5a). At low use rates, data
show that a single-use strategy is more beneficial
from an annual cost perspective. For 4 and 15
batches annually, that strategy is associated with
~27% and ~10% lower costs, respectively, than
with a stainless steel strategy.
The main reason for the lower cost with single-
use equipment is less time spent on equipment
qualification. For stainless steel equipment, over
three times as much time is spent on qualification
activities. When that time is translated to cost, the
resulting annual cost for maintenance of stainless
steel equipment is 21 times higher than that for
single-use equipment. Maintenance cost remains
constant regardless of equipment use rate. As use
rate increases, however, the difference between
stainless steel and single-use strategies levels out.
At 30 batches annually, their annual costs are
more or less equal.
As the number of batches increases, the
stainless steel strategy is a feasible alternative up to
100 batches annually, when the production
capacity becomes limiting for that scenario. For
capacity needs over 100 annual batches, the single-
use strategy would be the preferred alternative. For
an extreme case in which a facility is not used at
all during a whole year, our model shows that the
annual costs for capital investment (assuming a
10-year depreciation cycle and interest rate of
10%) and for qualification, annual maintenance,
and requalification are 122% higher for a facility
based on stainless steel equipment. So single-use
equipment offers flexibility and benefits at both
low and high capacity needs.
Profit: This study is based on fermentors at a
50-L scale, but few (if any) manufacturing
processes run at this scale. More appropriate 50-L
applications include process development, pilot-
scale production of clinical material, and seed
preparations for larger-sized fermentors. However,
GE Healthcare’s analysts were interested in profit
dynamics of single-use and stainless steel
strategies, so they performed a profit calculation.
Revenue of one million US dollars was assumed
for each batch, and the production cost was
subtracted from that to obtain a gross profit figure.
This calculation was performed for both the
stainless steel and single-use scenarios in a single-
product facility, and the result was plotted against
total capacity use for both scenarios (Figure 5b).
Clearly, the profit opportunity is higher for the
single-use alternative. Increased batch throughput is
the main reason for that outcome, in which benefits
essentially outnumber the slightly higher production
cost per batch for the single-use scenario.
Discussion
GE Healthcare analysists set up a model to
understand the cost and capacity implications of
single-use equipment in microbial fermentation
processes compared with reference scenarios based
on stainless steel equipment. The main conclusion
from this study is that a substantial amount of
time can be saved with single-use equipment. For
a single-product facility based on single-use
equipment, batches can be harvested every second
day; with stainless steel equipment, harvest takes
place every third day. Thus, disposables enable a
relatively higher facility throughput. For a single-
product facility, 50% more batches (150 batches)
can be produced annually using single-use
equipment than with stainless steel equipment
(100 batches).
For a multiproduct facility, the capacity
difference is even more pronounced, with a
doubled annual throughput with single-use
Table 5: Disposables, facilities, and chemicals included in this
study (NA = not applicable)
Unit Operation
Stainless
Steel
Single-
Use
XDA single-use fermentor bag NA Included
Plus Quad MBA single-use mixing
bag for medium preparation
NA Included
Probe sheath NA Included
Tap water for CIP (NaOH/acid
solutions)
Included NA
WFI for CIP (final rinse) Included NA
NaOH solution for CIP Included NA
Acid solution for CIP Included NA
Black steam for heating of CIP
solutions
Included NA
Steam for SIP Included NA
Plant steam for system heating
during fermentation
Included NA
Air vent filter inlet (Sartofluor
Junior, Sartorius Stedim Biotech
GmbH)
Included NA
Air vent filter outlet (Sartofluor
mini, Sartorius Stedim Biotech
GmbH)
Included NA
GE ULTA HC, 6-inch filter for
medium transfer to system
NA Included
9. December 2015 13(11)si BioProcess International 7
equipment (135 batches) relative to stainless steel
(67 batches). The higher productivity of a single-
use facility is related to omitting the need for
equipment cleaning and cleaning validation
procedures after a campaign.
In a facility based on stainless steel, the final
equipment clean-in-place (CIP) procedure at the
end of each campaign is followed by cleaning
validation. Equipment swab samples commonly
are analyzed for total organic carbon (TOC), and
final rinse water typically is analyzed for both
TOC and endotoxins. Analytical results are
usually available five days after sampling. The
time for carry-over calculations, reporting, and
quality assurance (QA) approval of the resulting
report is estimated to take an additional two days.
So this seven-day cleaning validation procedure is
significantly reduced or eliminated by a single-use
fermentor, in which all materials that come into
contact with process fluids are disposed of after
use. During the downtime of that stainless steel
fermentor, a single-use
fermentor can be up and
running to produce additional
batches.
In a multiproduct facility, not
only the equipment, but also the
production suite needs to be cleaned
before starting a new campaign for a different
product. Facility cleaning procedures include
emptying production suites followed by cleaning
of walls, ceilings, and floors. Cleaning verification
is conducted through environmental monitoring
performed by quality control (QC) personnel.
However, the environmental risk from a
production suite can be assessed from previous
analytical results. The final QC results and QA
approval of the environmental monitoring report
therefore are not required typically before starting
a new campaign. Instead, the critical activity is
equipment cleaning and associated validation,
which become the limiting factors for facilities
special
report
Figure 4: Relative cost per batch in (a) single-product and (b) multiproduct facilities using either stainless steel (SS) or single-use
(SU) equipment; the cost for batch production using SS equipment is used as reference and set to 1.00 for all categories.
1.00
1.00
1.00
1.00 1.00
1.0
1.00
0.52
0.23
0.03
0.87 0.93
9.9
1.29
Capital
investm
ent
Qualifications,etc.
Annual
m
aintenance
and
requalification
Production
preparations
Production:
ferm
entation
Consumables
(disposables,
facility media,
chemicals, etc.)
Total
Total
Stainless steel
Single-use
1.00
1.00
1.00
1.00 1.00
1.0
1.00
0.39
0.17
0.02
0.84 0.93
9.9
1.25
(A)
(B)
Capital
investm
ent
Qualifications,etc.
Annual
m
aintenance
and
requalification
Production
preparations
Production:
ferm
entation
Consumables
(disposables,
facility media,
chemicals, etc.)
10. 8 BioProcess International 13(11)si December 2015
using stainless steel equipment due to the risk of
product carry-over. With single-use equipment,
however, that specific risk is nonexistent. A risk-
based strategy may be used for valuable time
savings, and a new campaign can be started the
day after sampling for environmental monitoring.
The improved productivity achievable with
single-use equipment also can have implications
beyond increasing the total capacity of a production
facility. During product development, for example,
shorter process times can contribute to significant
time savings and a decrease in overall development
time. That in turn can make positive financial
impact and speed access to market. With single-
use equipment, more batches can be produced in a
set product development period, allowing more
experiments to be conducted. That can generate
additional regulatory support data to aid in
development of a strong chemistry, manufacturing,
and control (CMC) documentation package. It also
can help to eliminate poor therapeutic candidates
earlier in development, ultimately saving money
that would otherwise be wasted on them.
When studying batch costs, GE Healthcare
analysts found that the total cost per batch at a
100% equipment use rate is 25–29% higher for a
single-use scenario than for a stainless steel
scenario. Consumables are the category that drives
most costs for single-use scenarios. That includes
disposable fermentor bags, mixing apparatus,
tubing, and sterile filtration consumables. However,
the fixed-cost burden — including capital
investment, annual maintenance, and qualification
costs — is higher for stainless steel equipment.
Those fixed costs remain whether or not a facility is
in use, whereas variable consumable costs incur only
when a facility is actually in use for production of
profit-generating biologics.
The implications of having a larger portion of
fixed costs rather than a variable operational costs
become apparent with production scenarios
running at a low facility use rate (e.g., in a start-up
company). At low facility use rates (<30 batches/
year), the annual costs are lower for facilities based
on single-use equipment. As the number of
batches increases, stainless steel equipment
becomes the less expensive alternative until the
point at which production capacity becomes a
limiting factor. In this process-economic model,
that point comes at 100 batches/year. If a higher
production capacity is required, single-use
equipment again becomes the preferred option.
The vast majority of microbial-based GMP
manufacturing processes are performed at scales
much larger than 50 L. However, an initial
assessment of profit dynamics shows that profit
opportunity is higher for a single-use strategy than
for stainless steel because of larger batch
throughputs. To examine process economics at
larger production scales, the model used herein
would be adjusted to each specific scenario.
However, the general principles applied in this
study should be valid for microbial fermentation
processes at all scales.
Choosing Single Use
Several conclusions can be drawn from these
results. A single-use equipment strategy is
Figure 5: Annual total production cost by (a) number of
batches produced and (b) annual accumulated profit against
total capacity use are analyzed for single-use and stainless
steel equipment. (a) Total production cost by number of
batches produced annually in single-use and stainless steel
scenarios; after 100 batches, the maximum annual production
capacity is reached using stainless steel equipment. With
single-use equipment, 150 batches can be produced annually.
(b) Total accumulated profit is plotted against total annual
capacity use; for the stainless steel scenario, 100% capacity
represents 100 batches; for the single-use scenario, 100%
capacity represents 150 batches.
0 100 200
TotalAnnualProductionCost
Batches
Stainless steel
Single-use
400 100806020
AccumulatedProfit
Capacity Use (%)
Stainless steel
Single-use
(A)
(B)
11. December 2015 13(11)si BioProcess International 9
advantageous in microbial fermentation under the
following conditions:
• When a certain number of batches must be
produced in the shortest possible time (single-use
equipment offers an agile solution, for example, in
early product development, production of clinical-
trial or toxicity study materials, or in vaccine surge
capacity scenarios)
• When high production capacities are needed
(here, a single-use strategy enabled a 50% higher
batch capacity over stainless steel in a single-
product scenario and a 100% higher capacity in a
multiproduct scenario)
• At full facility use (profit opportunity was
higher for the single-use alternative, with 150
annual batches, than for the stainless steel
alternative, with 100 batches annually)
• If facility-use rates are low (lower up-front
capital investment and low costs for annual
maintenance and qualification lessens fixed costs
associated with single-use equipment compared
with stainless steel).
For Further Consideration: This modeling
exercise was instructive, and the scenario results
are informative. Both are thought-provoking.
Perhaps this discussion has prompted more
questions than it provided answers. Although the
model was created to be practical and unbiased, it
is still dominated by GE Healthcare’s preexisting
knowledge of current processes and workflows.
For practical reasons, it was also restricted to the
fermentation process only. Expanding the
application and implementation of single-use
technology to specific unit operation systems (e.g.,
bioreactors, purification, and so on) would provide
either a requirement or an opportunity to rethink
existing ways of working, depending on your
perspective.
Consider having a blank slate on which to
establish an ideal fermentation process based on
single-use technology. Is that ideal process founded
on a scaled-out set of disposable fermentors, or does
it rely on one assuming the role of an N – 1 or N – 2
fermentor for seeding larger stainless steel
equipment? In either case, what is the most
beneficial working volume? Would the host
organism stay the same? Could an organism be
engineered to maximize the potential of a single-
use–based fermentation strategy? What would the
facility be like? Could it be fully optimized for
single-use technology implementation both up- and
downstream, from the ground up? Do microbial
fermentation processes demand a hybrid equipment
facility? How does the building
footprint of a scaled-out process
compare with that of a scaled-up
process? Would a corresponding
reduction in utility requirements
convert to even greater cost savings and
higher net profits? How much faster could
a drug be brought to market?
Regardless of the form that the ideal
fermentation process and facility might take,
single-use bioreactors have forever altered the
buyer–seller relationship. Shared information about
materials and process constituents, especially as
they relate to adverse interactions, has become
essential to end-product quality. Security of supply
is critical to both process development and
production. Supply agreements are important to
codifying physical supply and achieving appropriate
buyer cost targets. Single-use–based fermentation
stands to benefit from all this experience.
Disclaimer
Results and conclusions presented herein are valid for this
specific study only. Other study conditions and assumptions
could significantly affect the outcome. The overall finding of
this study is that despite the higher batch cost, single-use
fermentation equipment can generate more batches
annually. So if all batches lead to sold product, the single-use
alternative would contribute to a higher gross profit.
References
1 Application Note 29-0564-39 AB. Microbial
Fermentation in Single-Use Xcellerex XDR-50 MO Fermentor
System. GE Healthcare Bio-Sciences AB: Uppsala, Sweden,
September 2013; www.gelifesciences.com/gehcls_images/
GELS/Related%20Content/Files/1392320581787/
litdoc29056439_20140213234550.pdf.
2 Application Note 29-1341-11 AA. Comparable E. coli
Growth and Domain Antibody (DAb) Expression in Single-Use and
Stainless Steel Fermentor Formats. GE Healthcare Bio-Sciences
AB: Uppsala, Sweden, May 2015; www.gelifesciences.com/
gehcls_images/GELS/Related%20Content/
Files/1432051180778/litdoc29134111_20150519175927.pdf. •
Corresponding author Ken Clapp is senior global product
manager, Eva Lindskog is upstream marketing leader,
Kjell Eriksson is a senior scientist, and Sandeep
Kristiansson is a senior research engineer, all in life
sciences at GE Healthcare Bio-Sciences Corporation, 100
Results Way, Marlborough, MA 01752; 1-484-695-5844;
ken.clapp@ge.com; www.gelifesciences.com.
WAVE Bioreactor and Xcellerex are trademarks of GE
Healthcare. Biostat is a trademark of Sartorius Stedim
Biotech. C-Flex is a registered trademark of Saint-Gobain
Performance Plastics.
special
report
