FAQ & Troubleshooting

Using Auto control sets a parameter at a certain value dictated by the user, and the controller functions based off feedback from a given sensor to push that parameter towards the desired value (PID controller). For example, if agitation is set to Auto 40 RPM, the motor of the VW continues to update the power input until the desired RPM is measured by the sensor. If temperature is set to Auto 37°C, the heater power will adjust appropriately until the desired temperature is measured by the RTD, and it will continue to maintain it. The Manual control sets a parameter to a certain value dictated by the user and directly controls the output for the given controller. In Manual mode, the sensor only has a monitoring function.  For example, if agitation is set to manual 40%, the motor driving rotation of the VW will be powered at 40% duty. In the PBS-3, this corresponds to 22 RPM. If temperature is set to manual 37%, the heater will be powered at a constant 37% duty without interruption, and the temperature will exceed 37°C and continue to heat until it reaches a maximal point. For this reason Auto mode is the default and recommended control method. Input of each of the four gases (air, N₂, O₂, and CO₂₎ can also be manually adjusted using the Manual control.

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The software interface (Hello UI) allows for customizable programming of temperature, agitation rate, pH, dissolved oxygen (DO), gas flow rate, and displays the parameter’s set point (SP) and present value (PV) on the main screen. The software also controls the bioreactor’s built-in pumps and lights. Alarms, settings, and process recipes can be configured within the software using standard computational logic for “set it and forget it” operation. See the user manual for a full list of configurable settings and details on programming process recipes.

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Agitation rate is a key parameter in bioprocess design and must be optimized through experimentation according to your cell type, culture modality, and bioreactor scale. The publications listed under Resources > Publications have data from numerous cell types and bioreactor scales and include the agitation rates used. One guiding principle in choosing agitation rate is the culture should be homogeneous, with no density gradient due to gravity. If your culture looks more concentrated near the bottom and less concentrated on top, your agitation rate may need to be increased. Contact app.eng@pbsbiotech.com for agitation rate recommendations based on your process.

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The PBS-3 and PBS Mini single-use vessels are rigid vessels made of polycarbonate. The PBS-15 and PBS-80 single-use vessels are non-rigid bags made of polyvinylidene fluoride (PVDF) with a polycarbonate wheel, like the smaller systems.

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The patented VW impeller provides precise control over power input for optimized mixing which achieves a homogeneous cell culture environment. While many cell types can be grown in the VW Bioreactor System, it is especially advantageous for growing sensitive cell types such as pluripotent stem cells, due to the lower shear stress and more uniform energy dissipation rate throughout the full volume of the vessel. All VW Bioreactors, regardless of size, have the same vessel design and impeller shape, enabling smaller-scale bench-top units to serve as accurate scale-down models for early-stage process development. These processes can then be linearly scaled up to larger production units. This technology can speed up time to market by minimizing common challenges faced during technology transfer as processes scale up from the R&D stage to the GMP clinical and commercial manufacturing stage. Additionally, VW Bioreactor Systems offer a compact design, fully integrated controls, and an intuitive and user-friendly human-machine interface (HMI).

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The PBS Minis are intended to be used in an incubator controlled to the desired temperature, humidity, and CO₂ %. On all other bioreactors with fully integrated controls, the temperature of the culture can be set and maintained (in °C) using the automatic mode of temperature control in the bioreactor software. The resistive temperature detectors (RTDs) provide data in a feedback loop that continuously measures the actual temperature and compares it to the set point and adjusts the power to the heating unit along the bottom of the bioreactor housing accordingly. The PBS-3 unit has a thermowell in the single-use vessel into which a RTD  connected to the bioreactor housing is installed, while the PBS-15 and PBS-80 units have two RTDs built into the bioreactor housing that contact the back of the single-use vessel and are sufficiently insulated from the conductive metal housing to ensure that they accurately measure the temperature of the vessel.

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The computer-controlled bioreactors (PBS-3, PBS-15, and PBS-80) include pH and dissolved oxygen (DO) sensors. Both reusable sensor and single-use sensor models are available depending on the customer's request. The pH and DO sensors are integrated with the bioreactor software, and like temperature, can be set at specified set points. See the user manual for a detailed description of how pH and DO are controlled. The Minis do not currently support any PAT and must rely on the temperature, humidity, and CO₂ % of the incubator in which it will be used to control pH and DO.

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Each of the computer-controlled bioreactors can be hooked up to pressurized air, carbon dioxide, oxygen, and nitrogen gas. The composition of gases in the bioreactor headspace is dictated by the DO and pH set points, and the gas flow rate can be modified via the Main Gas controller. Sparging is also available; the pore size of the sparger is dependent on the model of bioreactor vessel. The Minis have caps with gas-permeable membranes, so their headspace gas is determined by the composition of gases in the environment they are used in. Testing has shown that VW Bioreactor Systems can achieve an oxygen mass transfer rate (k_La) of up to 20 hr⁻¹ using our microsparger elements.

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Yes, the VW impeller is integral to the single-use vessel design as it drives the flow of fluid inside the vessel.  The vertically oriented wheel rotates around a shaft that is anchored to the vessel, and rotation of the VW is driven by magnets.  

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We have performed biological testing in the VW Bioreactor Systems in parallel with other bioreactor systems to compare cell growth, productivity, and product quality. In addition, fluid dynamics studies have been performed at various scales to quantify mixing time and volumetric mass transfer rate (k_La). The fluid mixing pattern, shear stress levels, particle residence times, and kinetic energy dissipation rate profiles have also been investigated using computational fluid dynamics (CFD) modeling on ANSYS Fluent, MStar, and STAR-CCM+® software.

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The PBS-Minis require electricity (120 or 240V) and are meant to be operated within a temperature, humidity, and CO₂ controlled incubator. The computer-controlled VW Bioreactor Systems require electricity (120 or 240V) and pressurized gases to operate (gas pressure requirements are detailed in the user manual). They are designed to run with four gases (air, nitrogen, oxygen, and carbon dioxide), but can be operated without nitrogen. They have an ethernet port to connect to networks for remote monitoring and control over the internet, but an internet connection is not necessary for operation.

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Our bioreactors have been designed for plug and play simplicity with our integrated software, so they are very easy to use. The VW Bioreactor Systems come pre-configured to customer specifications, and installation and system verification by a PBS service engineer takes approximately 4 hours to complete. Some of our customers have received VW Bioreactor Systems in the morning and inoculated them by the afternoon.

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All functions performed by the Hello UI can be performed on a DCS by configuring it to use HTTPS web calls. Contact app.eng@pbsbiotech.com for more details.

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There are three tiers of qualifications for PBS products: IA, FA, and GA. IA Grade products have limited certification or quality claim and are intended for early-stage R&D and process development. FA grade products are qualified for clinical use and are intended for customer “First in Human” use of therapeutic drug product. GA grade products are qualified for cGMP use and are intended for customer commercial cGMP use for the therapeutic product they manufacture.

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Extractables testing is performed   on our GA Grade single-use vessels in accordance with USP<665>, USP<1665>, and recommendations from the Bio-Process Systems Alliance (BPSA) and BioPhorum Operations Group (BPOG). Our test approach has been reviewed by consultants specializing in single-use validation, and the testing is performed by a highly reputable contract laboratory specializing in extractables testing.

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VW Bioreactor Systems can be operated as closed systems and can handle high containment requirement applications as well as cGMP operations. The low shear environment in the VW Bioreactor and the platform’s scalability can potentially expedite and improve virus and vaccine production.

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Comprehensive installation and operational qualification (IQ/OQ) packages are available, as well as the option to customize your equipment qualification. The IQ/OQ provides documented verification that the VW Bioreactor System as well as the facility requirements it interfaces with (electrical power, pressurized gases) have been correctly installed and the VW Bioreactor System can consistently operate within established limits per the PBS Biotech recommendation. A PBS service engineer or certified service provider is responsible for completing the equipment qualification in your facility.

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Each single-use vessel is double-bagged and sterilized by gamma radiation prior to shipment to the customer. The stainless-steel bioreactor housing is never in contact with process fluids and can be wiped down with 70% reagent alcohol like most pieces of laboratory equipment.

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Thanks to the unique design of the VW impeller, the mixing characteristics of the VW Bioreactors are very homogeneous across all scales. This includes mixing time, average shear rate, and turbulent energy dissipation rates. This homogeneity greatly facilitates process scale-up from small development volumes (100mL) to full production volumes (3-80L).

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VW Bioreactor Systems have proven capable of supporting viable cell densities exceeding 4×10⁶ cells/mL (iPSCs) and 2×10⁶ cells/mL (MSCs). Other tests have shown comparable cell growth performance and productivity between the VW Bioreactor System and other systems currently on the market, which include both traditional stainless-steel tanks and other single-use systems.

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All VW Bioreactor vessels contain a novel, vertically oriented impeller with bi-directional vanes that rotates via magnetic coupling around a fixed shaft to mix vessel contents.

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Yes, on a case-by-case basis we can accommodate some customizations that do not require significant structural alterations. Contact sales@pbsbiotech.com for custom configuration pricing.

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We strive to ensure all of our customers have the resources they need for success. Our Applications Engineering team can provide in-person and remote support for any questions or issues that arise with the VW Bioreactor System. Our Process Development team has experience with numerous cell types and bioprocess technologies and can be consulted on bioprocess design, scale-up strategies, and cell culture operations. For more significant support, the Process Development team can be contracted to develop and scale-up processes using your cell line in our state-of-the-art research laboratory.

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Contracts vary depending on the scope of the project, but a typical process development contract lasts 4-6 months.

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No, the PBS-80 bioreactor is intended to be placed on the floor and comes on locking casters to facilitate mobility when needed. The footprint of the PBS-80 is width: 93 cm (36.5 inches), depth: 55 cm (21.5 inches), height: 146 cm (57.5 inches).

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For non-GMP units, the bioreactor can be controlled and monitored remotely through a secure web-based connection to a computer, tablet, or phone. GMP-configured units can also be accessed remotely but require someone to physically grant access from the bioreactor touchscreen.

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Yes, the PBS-15 housing’s compact footprint is designed to fit on standard lab benches or carts. The footprint of the PBS-15 is width: 66 cm (26.0 inches), depth: 42 cm (16.5 inches), height: 90 cm (35.5 inches).

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The type and frequency of process data stored on the bioreactor’s hard drive can be customized through the software. All user logins, changes, and data histories follow 21 CFR Part 11 requirements. Process data, user events, and error logs are formatted in CSV files and can be downloaded to a local computer through direct LAN connection or exported to a USB drive.

For non-GMP units, the bioreactor can be controlled and monitored remotely through a secure web-based connection to a computer, tablet, or phone. GMP-configured units can also be accessed remotely but require someone to physically grant access from the bioreactor touchscreen.

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The AHHV is a sterile-contained retractable valve that can be used to perform a full vessel harvest, medium exchange, and sampling in the PBS-15 and PBS-80bioreactors. When the bioreactor is in Harvest Mode, agitation stops and the AHHV can be raised through the Harvest Channel in the Vertical-Wheel, extending up to 7 inches above the bottom of the single-use bag. The AHHV can still be used while agitation is ongoing, but only to a height of up to ½ inch, and extra care must be taken that the AHHV does not impede rotation of the Vertical-Wheel.

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Yes, the housing’s compact footprint is designed to fit on standard lab benches or carts. The footprint of the PBS-3 is width: 38 cm (15.0 inches), depth: 48 cm (18.5 inches), height: 67 cm (26.5 inches).

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The PBS-3 vessel has multiple ports at different heights to take samples, perform medium exchanges, and perform full vessel harvests. There are port locations on top of the vessel lid and on the back of the vessel connected to weldable tubing. Port configurations depend on the vessel model; contact app.eng@pbsbiotech.com for full details of your vessel configuration. In general, samples are taken through the dip tube using the built-in peristaltic pumps or pulled through the sampling line using a sterile syringe. The sampling and harvest lines’ distal ends are made of weldable tubing. Note: there is no adjustable height harvest valve (AHHV) available in the PBS-3 bioreactor.

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Each Mini base unit has a cable ending in a female adapter that plugs into a DC power adapter unit, which in turn can be plugged into a wall outlet. The power accessory cable can accommodate up to four female adapters from four different Mini bases and consolidate all four into a single DC power adapter with single outlet plug.

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It is possible, but we do not recommend reusing vessels due to the risk of contamination from previous cell cultures or washing chemicals. PBS vessels should not be autoclaved, the heating process will demagnetize the VW and impact its magnetic coupling to the Mini Base.

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While everyone’s cell culture process will have different requirements, we recommend keeping at least two weeks' worth of vessels in stock. Please contact our Applications Engineering team (app.eng@pbsbiotech.com)  if you would like assistance in determining your predicted usage of vessels.

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A VW Bioreactor System is comprised of a reusable hardware component (the bioreactor housing), specialized application software, and single-use vessels to manufacture your cell therapy product.

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The VW Bioreactor System is incredibly versatile: MSCs, PSCs, native immune cells, and differentiated cell types including T cells, NK cells, chondrocytes, adipocytes, and beta islet cells have all been cultivated in VW Bioreactor Systems. Cells have been grown in aggregates, on microcarriers, as embryoid bodies, and as mixed-population cultures in batch, fed-batch, and perfusion modes.

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Yes, process development and service contracts are entirely dependent on customer needs. We have helped clients in early R&D with process development, scale-up, optimization, and characterization, and clients in clinical manufacturing including first-in-human studies.

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• Cell thawing and inoculation
• Creation of laboratory working cell bank (L-WCB)
• 2D and 3D culture seed train optimization (T-flasks, multi-layer vessels, well plates)
• 3D expansion (microcarrier, aggregate, single cell suspension, embryoid body (EB))
• Differentiation
• Passaging (single cell, clump, 3D to 3D transfer)
• Medium exchange (fed-batch, bolus, perfusion, dilution)
• Dissociation and harvest
• Downstream processing (wash/separate/concentrate)
• Cryopreservation
• Analytics (product identity/quality/activity)
• Closed-system processing
• Process characterization and risk assessment
• Scale-up of existing processes
• Tech transfer through detailed protocols and batch records

• Wilson Wolf G-Rex® Well Plates
• Carr Biosystems UFMini®
• Sartorius Ksep® 400
• Cytiva Sefia™ S 2000
• Fresenius Kabi Lovo®
• Gibco™ CTS™ Rotea™ Counterflow Centrifugation System
• Flow cytometry (BD Biosciences Accuri™ C6, OrfloTechnologies Moxi GO II)
• Microscopy (fluorescence, time-lapse, automated confluencymeasurement)
• Biorep Automatic Islet Cell Counter
• Automated cell counters (NC-250, NC-200, ADAM-MC,hemocytometer)
• Media analysis (Nova Biomedical BioProfile® FLEX2,osmometer, pH meter)
• Tube welders and sealers, aseptic connectors
• T-flasks and multi-layer vessels
• and many more

The floored impellers have panels going around the circumference of the impeller in between each baffle, connecting the two exterior circles. The floorless impellers have no panels, so the space between each baffle is empty. The below image highlights this difference. The floorless VW impellers allow for more shear force in the vessel which leads to forming smaller pluripotent stem cell aggregates than the floored VW impellers at equivalent agitation rates.

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Any cell therapy process that is ready to be scaled up from the PBS-15 for clinical studies or commercial-level production.

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When properly maintained and used correctly, there is no significant difference insensitivity and functionality between reusable (Broadley-James) and single-use (Hamilton) pH and DO sensors. This is based on internal testing and product quality assurances from third party providers of sensors.

The floored impellers have panels going around the circumference of the impeller in-between each baffle, connecting the two exterior circles. The floorless impellers have no panels, so the space between each baffle is empty. The below image highlights this difference. The floorless VW impellers allow for more shear force in the vessel which leads to forming smaller pluripotent stem cell aggregates than the floored VW impellers at equivalent agitation rates.

Any cell therapy process that is ready to be scaled up from the PBS-3 for clinical studies or commercial-level production.

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When properly maintained and used correctly, there is no significant difference in sensitivity and functionality between reusable (Broadley-James) and single-use (Hamilton) pH and DO sensors. This is based on internal testing and product quality assurances from third party providers of sensors.

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Depending on the target batch size, the PBS-3 bioreactor can be used for production of cell therapy products for use in clinical studies (including first-in-human trials), or for continued process development and optimization for larger volume processes.

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Bring a Mini base inside a biosafety cabinet (BSC) and turn agitation on to 110% of the culture agitation set point (e.g. if the culture agitation rate is 60 rpm, the sampling agitation rate should be 66 rpm), then bring the Mini vessel from the incubator and place it on the Mini base in the BSC. Remove samples through the port using a vertically oriented serological pipette with the tip just above the wheel. For accurate sampling, do not overshoot your target sample volume and then return some of the liquid back into the vessel- either dispense the entire sample back into the vessel and try again, or make not of the actual sample volume and use the actual volume for calculations. Return the Mini vessel to its Mini base in an incubator as soon as possible to avoid cell settling or temperature drop.

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The PBS Mini base and vessel are intended to be placed in an incubator for control of temperature, humidity, and headspace gases.

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The PBS Minis are best suited for process development and optimization at small scale, and as scale-down models for larger volume processes.

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