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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_101_библиотеки_им_акад_М_И_Перельмана
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The bioreactor vessel’s size is crucial in determining the impeller diameter, with a common
guideline being that the impeller should be approximately one- third of the vessel’s diameter.
The combination of the sparger, impeller, and bafes plays a signicant role in determining
mixing and oxygen transfer efciency in stirred- tank bioreactors.
10.13.2 aeRation
Aeration provides the necessary oxygen for cells’ aerobic requirements as oxygen is an essential
substrate for cell development and maintenance in bioreactors. Dissolved oxygen, often referred to
as DO, is the primary oxygen source that cells receive in both free and noncompound forms. Hence,
one of the critical functions of bioreactor systems is to continuously supply dissolved oxygen to
cells through aeration. In industrial bioprocesses, the most common methods for this are using air,
air- enhanced oxygen, or pure oxygen.
Aeration occurs in the bioreactor when oxygen diffuses into the cell culture medium at the interface created by the overlay.
The oxygen from the spargers dissolves in the cell culture with the help of agitation.
The total gas ow rate through the sparger varies depending on the type of sparger. For instance,
a ring sparger typically has a volume of air per volume of liquid per minute ranging from 0.1 to 0.3
vvm, while a microsparger recommends a maximum gas ow rate of 0.03 vvm for mammalian cell
culture processes. Microbial processes can utilize an aeration rate between 0.5 vvm and 2.0 vvm.
This aeration rate can also vary signicantly during fermentation to accommodate the increase in
cell density.
The physicochemical features of the cell culture medium, the geometrical parameters of the
bioreactor, and the presence of cells all have an impact on the rate of oxygen transfer (OTR) from
gas to liquid interface. The OTR is critical to bioreactor design and scale- up. The DO in the culture medium depends on the OTR and its consumption by the cells (oxygen uptake rate). Agitation
disperses the oxygen bubbles and promotes the gas bubbles’ mass transfer through the gas-liquid
(cell culture medium) interface. The movement of the bubble through the gas- liquid interface and its
diffusion through the liquid membrane surrounding the cells into the cytoplasm enable oxygen to be
transferred from a gas bubble to the cell. The oxygen uptake (or utilization) rate (OUR) is most often
cell dependent. Therefore, monitoring the OUR is essential to assess the viability of the culture.
The rate of oxygen uptake can be expressed as follows:
Where qO2 is the specic uptake rate of oxygen, X is the biomass concentration and, Y
oxygen yield coefcient.
The oxygen uptake rates of cell lines typically used in biomanufacturing are summarized in
Table 10.9.
The oxygen transfer rate (OTR) is given by
OTR = kLa (C*- CL) Equation 10.5
where C* is saturated DO concentration, CL is the actual dissolved oxygen (DO) in the culture
medium, and kLa is the volumetric mass transfer coefcient.
When oxygen transfer is the rate- limiting step, OUR is balanced by OTR
OUR = OTR Equation 10.6
OUR =Xq
X
=
O2
Y
XO
/
2
Equation 10.4
is the
XO/
2
=−
()
×
dt
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TABLE 10.9
219
Oxygen Uptake Rates of Cell Lines
Cell Line OUR [10−3 mol/ cell/ h]
CHO DG44 2
CHO 5.0– 8.04
NS0 myeloma 2.19– 4.06
MAK hybridoma 4.16
FS- 4 (Human diploid cells) 0.5
HFN7.1 Hybridoma 2.0
Source: What do cells need from a bioreactor? (GElifesciences.com)
Cytiva LifeSciences, Rufeux, P. A. et al. and Xiu, Z. L. et al.
µ
X
Y
YOTR =CellGrowthRate
X/O2
XO/
2
kC*C
La L
Equation 10.7
Equation 10.8
The mass balance for dissolved oxygen in a well- mixed liquid phase is given by
dC
OTROUR=−
Equation 10.9
Where dC/ dt is the accumulation of oxygen rate in the liquid phase.
The mass transfer coefcient, represented by kLa, correlates the oxygen transfer rate with the
oxygen uptake rate. kLa depends on various factors, including bioreactor size, media composition, cell type, presence of salts and surfactants, pressure, temperature, agitation speed, aeration
rate, and other geometric and operational features. Achieving a high kLa is crucial for bioreactor
design and scale- up success. Various physical and chemical methods can measure kLa, such as
the unsteady state, steady- state, dynamic, dynamic gassing- out and pressure step, sodium sulte
oxidation, carbon dioxide absorption, and catechol bio- oxidation methods. Changes in specic
process parameters can impact kLa, and these must be considered when evaluating different bioreactor systems or scaling up operations. Typically, kLa should be maintained constant during
scale- up, as other physicochemical parameters like pH, DO, temperature, and bioreactor geometry are adjusted to achieve the required oxygen transfer rate. If bioreactor designs vary, kLa
serves as a metric to guide adjustments to gas ow rates, sparger designs, and more to maintain
the desired cell density. The optimal conditions for cell growth are typically met when OTR
exceeds OUR.
The key variables that can affect kLa include:
• Gas Flow rate: A higher oxygen supply increases the kLa, powered by increasing the
bioreactor’s oxygen supply. The oxygen supply may be regulated by changing the concentration, i.e., air versus oxygen and volumetric ow. However, careful evaluation and balance are
required to ensure that these changes do not impact the cell culture negatively. For example, a
high ow rate could lead to excessive foaming and may also cause cell damage.
()
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• Mixing: Mixing is key to ensuring homogeneity and eliminating concentration gradients
within the bioreactor. The impeller type, location, and speed can impact the mixing dynamics
and gas dispersion. kLa increases with tip speed in general; however, tip speed is also proportional to shear forces which can cause cell damage. Therefore, different impeller types
and their placements are considered in bioreactor design to ensure these shear forces are not
generated while achieving the target kLa.
• Gas bubble size: The gas bubbles that are smaller in size can remain in the culture medium for
a more extended period. This increase in residence time increases the kLa.
• Temperature: The kLa and oxygen solubility in the culture media is inversely inuenced by
temperature. The oxygen solubility in pure water diminishes.
• Sparger: The number of spargers, the pore size, and surface area are factors that inuence the
bubble size, ow rate, which in turn impacts the kLa.
The kLa measurement helps determine the optimum oxygen supply that can support cell growth.
10.13.3 teMPeRatuRe contRol
Bioreactors commonly use 316 stainless steel for their wetted components. Heat transfer is necessary to regulate and maintain a consistent temperature during fermentation, which is vital for
both mechanical agitation and exothermic metabolic activity that generates heat. Most bioreactor
designs incorporate a jacketed vessel that circulates a temperature- controlling liquid (e.g., glycol
or water) externally connected to the bioreactor to facilitate heating and cooling. In some cases,
internal heat transfer coils are used, but microbial growth within the coils often hampers heat
transfer efciency.
The heat is transferred from a heat- transfer uid to the reactor material through the heat- transfer
surface or from the fermenter material to the cooling uid if cooled. Therefore, the rate of healing
depends on the bioreactor volume.
The heat required to heat up or cool down the contents of the bioreactor is represented by the
following equation:
Q = m x cp x (T0 − T1) = m x cp x ΔT Equation 10.10
Where Q is the heat (J), m (kg) = mass of the substance, cp, (J/ kg K) = specic heat capacity of the
substance, T0 and T1 (K) = start temperature and end temperature, respectively, and
If the substance’s specic heat capacity is unknown, then the heat capacity of water is used.
In a fermentation process, cells (irrespective of the microorganism or cell type) have an optimal
temperature range that supports their growth. If the temperature is below this range, then the slow
growth can reduce the rate of cell production or product synthesis. On the contrary, if the temperature is too high, it can lead to cell death and impact product quality.
The net cell growth rate is expressed as follows:
where X and t are cell concentration and time, µ and kd are cell growth and cell death rate,
respectively.
ΔT (K) = temperature change
dX
kd,=−
µ
X
Equation 10.11
∆
HY
HX
,/
=+
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Here, the cell growth, cell death rates are both temperature- dependent and expressed as functions
of temperature following the Arrhenius equation:
μ = A x e
kd = A′ x e
(−E
/ RT)
Equation 10.12
a
(−E
/ RT)
Equation 10.13
d
The heat generated during a microbial fermentation process is given by the following
equation:
H
cS
Where ΔH
ΔH
is the heat of the cells’ combustion, and YF
c, X
is the heat of combustion of the substrate, YF
c, S
YF
XS
/
,
∆
F
cX
is the metabolic heat evolved per gram of cells
H/ X
is the substrate yield factor.
x/ S
Equation 10.14
produced (Figure 10.24).
For mammalian cell culture processes, particularly CHO cell lines, the optimal temperature for
cell growth and culture maintenance is typically around 37ºC. However, lower temperatures have
been shown to extend cell culture viability, although cell growth may not be as robust at 37ºC.
Lower temperatures can effectively slow down the decrease in cell viability while allowing the cells
FIGURE 10.24 Effect of temperature on the cell growth rate for E. coli
Source: Processes 2020, 8(1), 121; https:// doi.org/ 10.3390/ pr801 012; http:// crea tive comm ons.org/ licen ses/
by/ 10.0/
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to remain in the production phase for protein synthesis for a longer duration. Several studies have
demonstrated the impact of temperature on protein synthesis or improving the specic productivity
of cells. A successful cell culture process, depending on the specic protein and cell line, may initially begin with temperature control at 37ºC to primarily support cell growth and achieve higher
densities. Later, the temperature can be adjusted to a lower range to enhance specic productivity.
However, the ideal temperature should be evaluated for each cell culture process to ensure it doesn’t
affect product quality.
10.13.4 Ph contRol
Similarly to temperature, different biological systems have an optimal pH range. pH levels continually uctuate during the fermentation process, with many processes requiring constant pH
maintenance. Metabolite or by- product accumulation and substrate consumption often lead
to shifts in pH in the culture medium. For instance, in microbial fermentation, acetic acid/
carbon dioxide accumulation can decrease pH, and ammonia consumption can also lower pH.
Consequently, continuous monitoring and pH adjustment are necessary. In mammalian cell culture, glucose consumption leads to lactate accumulation, resulting in pH reduction. pH control is
achieved by adding a base or an acid to the bioreactor. Most modern bioreactors utilize a control
strategy that automatically adjusts pH using a feedback control loop. In mammalian cell culture
processes, sodium bicarbonate is commonly employed to counteract the acidic effects of lactate
accumulation and CO2.
Additionally, CO2 may be added for pH control, but caution is needed to avoid oxygen depletion,
which can impact dissolved oxygen (DO) levels and the culture medium balance, requiring signicant amounts of sodium bicarbonate for buffering. Maintaining the pH of the media is critical for
the success of the cell culture process, as even minor pH changes can affect cell growth, protein
production, and product quality.
10.13.5 foaM contRol
Foaming is a common issue in the fermentation process. The combination of agitation and aeration,
along with foam- producing and foam- stabilizing chemicals (such as proteins, polysaccharides, and
fatty acids), can lead to substantial foam formation in the bioreactor. Excessive foaming can block
outlet gas lines and lters, resulting in the loss of fermenter contents, increased equipment pressure
that can be detrimental, and potentially providing a route for contamination. Antifoam agents are
widely used and added either at the start or during the manufacturing cycle, depending on the level
of foaming. Adjusting the agitation rate can also help control foaming to some extent.
In certain cases, cell culture media may be supplemented with antifoam agents (e.g., pluronic
acid) before use to minimize foaming. However, antifoam agents can also negatively affect oxygen
transport rates and downstream processing due to membrane fouling. Mechanical systems, such as
high- speed spinning disks at the top of the reactor, are suitable for addressing mild foam accumulation but consume signicant energy in large- scale bioreactors.
Uncontrolled foaming can rise and potentially wet the exhaust lters, causing clogs and increased
pressure in the bioreactor or, worse, contamination. Ensuring adequate headspace in a bioreactor
allows gas to disengage from the liquid, helping to minimize foaming, especially in large- scale
bioreactors.
10.13.6 contRolleR systeM
Monitoring bioreactor process parameters is crucial to maintaining optimal conditions that support
cell growth and product synthesis. The most common instruments required for bioreactors are
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related to the physical factors discussed earlier: temperature, agitation, gas ow, and pressure. The
fundamental parameters that should be monitored include pH, temperature, and dissolved oxygen
(DO). Modern bioreactor designs incorporate new probes and techniques for measuring these
parameters and additional metabolites effectively. This involves a combination of online and ofine
measurements using sensors and probes that provide feedback to the control system. A controller
integrated with the bioreactor vessel is responsible for monitoring and controlling these parameters,
adjusting them to match the user- dened set point. The sensor and control components of the bioreactor platform, connected to the controller, provide the necessary input and output, forming the
control loop. This control loop serves as the medium for process control to ensure system stability and consistent performance. Control loops offer opportunities to enhance process operations.
For stable operation, basic control loops for temperature, pH, dissolved oxygen, and agitation
are integrated into bioreactor systems. Analysis of this monitoring provides valuable feedback to
operators, leading to a deeper understanding of the process and improved stepwise operation. There
are two types of control mechanisms: open- loop and closed- loop. In an open loop, the controller’s
actions are unaffected by the process variable. In a closed- loop system, the controller’s actions
depend on the setpoint (desired value) and the process variable. Feedback or feedforward loops can
be used in a closed- loop system.
In bioreactor systems, the feedback closed control loop is the most common control technique. In
this approach, the measured output is continuously examined in a time- dependent manner (typically
every second) using a feedback element (i.e., sensor). The value is then compared to the setpoint,
and the difference between the measured and setpoint values is fed back into the controller. The controller adjusts the control element to produce the corrected response, which is then fed back into the
process. PID controllers (proportional- integral- derivative) are commonly employed in this context.
The other type of control system is feedforward, in which the input is measured by a sensor
before being introduced into the process. If necessary, the value is adjusted by the controller and
control element to input the control signal into the process. Unlike the feedback loop, there is no
measurement of the output in this system (Figure 10.25).
These sensors and probes must be either pre- sterilized (gamma irradiated) or sterilized before use
in the process. The insertion of these components should not compromise the sterility of the bioreactor vessel. This may require the use of aseptic connectors or steam sterilization of the bioreactor
with the probes/ sensors installed. The components must be able to withstand high temperatures
(121°C) and humidity. Autoclavable and sterilized- in- place bioreactors, as well as vessel sterilization and decontamination, make sterilization before use in the production process and decontamination after operations convenient. Insertable probes may not always be reliable, especially
for long- term mammalian cell culture processes, where probe performance may be a concern.
Some other issues with these probes include their positioning in the bioreactor vessel, probe drift
affecting their response, lack of in situ recalibration, and, most importantly, a potential route for
FIGURE 10.25 Illustration of a feedback control loop
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TABLE 10.10
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Summary of Process Parameters and Associated Measurement Components
Process Parameters Sensor Control Element
Temperature RTD Heating/ cooling jacket/ water reservoir
pH pH probe (optic and conventional) Pump for base addition and CO2 from the mass
ow controller
DO Polarographic oxygen sensor, DO electrode Oxygen mass ow controller
Glucose Spectroscopic sensor Pump for glucose solution
Gas ow rate Rotameters or mass owmeters Mass ow controllers
Weight Load cell Amount of liquid in the bioreactor vessel
Liquid ow rate Magnetic- inductive ow meter Flow valve
Pressure Pressure gauge Backpressure regulator in the exit gas line
contamination. SUBs are single- use bioreactors with pre- installed sensors (typically for pH, DO,
and cell density), as well as gamma- sterilized and ready- to- use assemblies. Setup and operation
are simplied with these single- use sensors. The Celligen BLU (Eppendorf), Cultibag and AMBR
(Sartorius), and Applikon Biosep (Applikon) have all successfully utilized pH and DO sensor spot
technology (Applikon Biotechnology) (Table 10.10).
The desired features of a control system and its components include precision and accuracy, ease
of installation and operation, scalability, compatibility with multiple platforms/ sensors/ probes (e.g.,
accommodating single- use or reusable sterilizable probes), and compliance with GMP standards.
In addition to online measurements, ofine measurements for cell density, glucose, lactate, and
other parameters are also conducted during bioreactor operations. These ofine measurements
can be used to validate online measurements and for sensor calibration. Several standalone offline instruments are used for these measurements. Examples include a cell density counter and
spectrophotometer for cell density measurements, NOVA, and YSI Biochemistry Analyzer for pH,
metabolites, and substrate analysis.
Over the past decade, signicant advancements have been made in this eld, and with the emergence of single- use technology, online measurements for pH, DO, gas ow rate, agitation rate,
temperature, pressure, and glucose concentration in the medium, as well as liquid ow rate, have
become possible. Incorporating these controls and data acquisition capabilities has been facilitated
by improved analytics. Suppliers and vendors (e.g., Sartorius, Cytiva, Thermo Scientic) have successfully integrated these controls and capabilities into their product offerings. In addition to these
advancements, ongoing progress is being made with instrumentation and control systems to fully
utilize these systems and move towards a more automated system that requires less intervention.
10.14 HARVEST AND CLARIFICATION SYSTEMS
The primary objective of the harvest process is to separate the cells from the media. In bacterial
cells, the product of interest is contained within the cells, whereas in mammalian cultures, the protein is secreted into the medium. The timing of the harvest process is determined based on culture
conditions, including cell density, cell viability, productivity, and protein quality. Several harvest
methods, such as centrifugation, sedimentation/ occulation, or newer alternatives like crossow ltration or ultraltration (e.g., depth ltration systems, hollow ber ltration systems), are commonly
used, depending on factors such as cell type, product of interest, processing time, and scalability.
While the primary recovery steps involve separating cells from the culture medium, a secondary
recovery step involves ltration of the harvest using a smaller pore size membrane in mammalian
cell culture processes. In microbial cells, biomass/ cells are subjected to cell lysis (chemical or a
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combination of mechanical and chemical) to recover inclusion bodies containing the protein of
interest. Chapter 5 provides a detailed description of various clarication/ harvest options and considerations for choosing a suitable harvest method for microbial and mammalian culture.
10.15 ANCILLARY AND PERIPHERAL EQUIPMENT
10.15.1 steRilization
In the context of industrial fermenters, associated ttings, and piping, in situ steam sterilization
under pressure, commonly known as SIP, is employed. When it comes to large- scale sterilization
of equipment and liquids, thermal inactivation is the preferred method, especially for media. This
involves introducing saturated hot steam into the vessel/ pipe to ensure even distribution throughout
the device, eliminating cold spots or dead ends. Successful sterilization requires steam to displace
the air in the vessel and pipes. In cases where heat- sensitive devices need sterilization, chemical
agents or radiation may be employed. However, it’s crucial to ensure that chemical agents don’t
leave any residue, which could be toxic to the culture or lead to product adulteration. Some of the
commonly used compounds for sterilization include ethylene oxide, 70 percent ethanol- water acidied at pH 2 with HCl, formaldehyde, and 3 percent sodium hypochlorite. Radiation sterilization
can take the form of gamma rays, electron beams, or UV light. It is an effective method for singleuse parts and lter devices, but it is not suitable for larger equipment due to operational challenges.
Additionally, radiation can penetrate materials more deeply.
Sterile ltration is a widely used method for both liquids and gases. When it comes to gases,
depth lters, surface lters, and membrane cartridge lters are commonly employed. Membrane
lters, designed with uniformly small pores, sieve out particles effectively. Pressure drop can affect
both depth and surface lters. It is essential to inspect all sterile lters for structural integrity before
and after each use. Common methods for assessing the integrity of sterile lters include bubble
point diffusion testing, forward ow tests, and pressure hold tests. Filtration with a 0.2– 0.45 μm
membrane lter can be utilized to remove microbiological components. Inlet and exhaust gases for
bioreactors are ltered using sterilizing grade lters. For bioreactor liquid feeds, such as bulk media
and heat- labile growth supplements, sterilizing grade lters are also employed. These lters can be
directly connected to a sterile line on the bioreactor using a tubing welder in disposable/ single- use
bioreactor systems.
When it comes to heat sterilization, the key parameters are sterilization temperature and exposure
duration. Higher temperatures result in shorter sterilization times for the same degree of effectiveness. There are two methods for heat sterilization: batch and continuous. In the batch method, steam
is directly sparged into the vessel, heating its contents to 121°C for a predetermined period (usually
10– 20 minutes), followed by cooling with water to return to optimal operating conditions. The use
of steam allows for rapid attainment of sterilization temperature. In the continuous method, a heat
exchanger is used for both heating and cooling in a continuous operation. Caution must be exercised
during heat sterilization, particularly with heat- sensitive materials. Continuous heat sterilization
offers energy savings and is a safer option for such materials.
10.15.2 cleaning- in- Place
Cleaning is a routine procedure for equipment that comes into contact with the product to prepare it for the next batch. CIP is performed without disassembling or disconnecting any parts
from the processing system. After completing batch operations, equipment used in upstream production processes, including fermentation production vessels, seed train bioreactors, centrifuges,
homogenizers, and tanks, are rinsed with dedicated cleaning agents suitable for the equipment. The
specic cleaning agent, required quantity, and incubation period must be specied and validated
for successful cleaning. All equipment cleaning for future production runs should adhere to this
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validated procedure. Commonly used cleaning agents include caustic soda (5 M NaOH) and phosphoric acid (20% w/ v). Equipment cleaning involves multiple steps performed under different
conditions, including peristaltic pump ow rates for circulating the cleaning agent, circulation times,
and, if applicable, temperature. The entire cleaning process can take from a few minutes to several
hours or even a day, depending on the contact time required for effective cleaning. A standard
cleaning process in the industry starts with circulating water through the system, followed by an acid
solution, puried water, and nally a caustic solution. pH and conductivity of the water are checked
periodically to ensure no traces of the cleaning solution remain. Chromatography columns, media,
and TFF systems also undergo similar cleaning using caustic solutions or a combination of cleaning
agents. Packed chromatography columns are often stored in a 0.1– 1.0 N NaOH solution.
10.15.3 PuMPs, valves, tubes, and PiPes
Pumps are routinely used in nearly all unit operations for liquid transfer and circulation. The choice
of pump depends on factors such as the nature of the uid, ow rate, and scale of the process.
Commonly used pumps include peristaltic pumps, diaphragm pumps, and rotary lobe pumps.
Peristaltic pumps, which do not come into contact with the product, use tubing and molded ow
elements for liquid transfer. However, they have limitations, especially with high viscosity uids,
and can generate shearing and tubing shedding due to pulsing, potentially exposing the liquid. It’s
important to select the right pump head conguration and tubing. Disposable/ single- use peristaltic
pumps with single- use ow channels are available. Diaphragm pumps are positive displacement
pumps that use the reciprocating motion of the diaphragm and valves to pump uids, making them
suitable for high viscosity liquids. Centrifugal pumps, on the other hand, rely on rotational energy
from impellers and are best suited for high ow rates and low viscosity liquids. Further details on
pumps are discussed in Chapter 6.
Sanitary ttings, primarily constructed from stainless steel alloy, are commonly used in bioreactor frameworks, tri- clamp connections, and skids. These ttings typically include elbows, Tshapes, Y- connectors, and reducers. The choice of piping and tting depends on the specic unit
operation requirements. Fittings used in contact with the product must be sterilized before reuse.
Tubing and hoses are employed for liquid transfer. Tubing is typically considered a single- use
item and is made from various materials, such as elastomer and silicone, depending on process
requirements. In contrast, hoses can be single- use or reusable and are often used for air/ gas transfer
due to their ability to withstand high pressure and steam. Tubing and hoses are commonly used in
various bioreactor operations, including media and feed transfer, inoculum transfer between seed
and production bioreactors, air supply to bioreactors, and harvest. Valves are another crucial component, especially in bioreactors for process and ow control. These include sampling valves, drain
valves, and pinch valves. Valves can be potential sources of contamination, so it’s important to use
sterilizable materials, especially for valves reused in the process. The inner surfaces of bioreactor
vessels should be smooth and are often electropolished. O- rings are frequently used for small gaps,
such as in process control probes, while gaskets are employed for larger openings, such as pipe
connections to tanks and agitators.
10.16 SUMMARY
Bioreactor design has evolved over the years, incorporating in- line measurements, spectroscopy,
and the constant emergence of advanced sensors and probes to enhance process control. Efforts
are ongoing to integrate spectroscopy and advanced sensors to improve process control further.
New bioreactor designs and models aim to handle higher cell densities resulting from perfusion
by offering improved mixing and volumetric mass transfer coefcients (KLa) for oxygen transfer.
Sparger and impeller designs are areas of interest in bioreactor development. Single- use systems
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have gained acceptance in the late development landscape due to their potential to increase manufacturing capacity. Evaluation of cGMP compliance should be part of bioreactor design considerations.
Single- use bioreactors have gained greater acceptance in the industry, particularly in the past
decade. These systems have undergone signicant design enhancements, including improved mixing,
efcient gassing, and leak- free performance to sustain long- term high- density cultures. Many of
these changes are driven by the need to expedite processes due to advancements in cell lines, product
compositions, and increased use of perfusion. Computational uid dynamic modeling and other
advanced techniques have been instrumental in optimizing bioreactor design. Another focus area
has been optimizing shear while improving cell retention, especially in perfusion systems. Recent
trends include using a xed- bed bioreactor coupled with an automated tangential ow ltration concentrator to improve retention without increasing shear, resulting in enhanced process efciency,
reduced operating costs, and a smaller process footprint.
In general, the industry is moving towards intensied, connected, and continuous bioprocessing,
with a focus on enhancing process intensication. Concepts such as automatic perfusion systems
integrated directly into bioreactor platforms are becoming more common. The near future is
expected to witness the broader adoption of continuous bioprocessing, where unit operations and
processes are performed continuously, enhancing bioreactor capabilities and ancillary components.
These modications are likely to increase facility usage, reduce downtime, and maximize overall
productivity. Collaboration between biopharmaceutical manufacturers and single- use suppliers is
crucial to achieving these improvements, which are essential for a more robust process.
Understanding the capital costs associated with installing new equipment in an existing manufacturing facility and the costs of consumables for solutions or process additives is essential when
selecting unit operations. Therefore, process design must take a holistic approach to consider all
these factors.
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