Facility Design for Bio-Manufacturing

CMOs can design for disposable components

By Tony Garbarino and Dave Odegaard

In the biotechnology market, contract manufacturing facility design offers different design challenges from that of a traditional manufacturing company. Disposable technologies play an increasingly important part in the design equation.

Biotechnology companies often utilize contract manufacturers to produce the volumes of drug product required for clinical phases. If the drug shows commercial promise and receives marketing approval from the regulatory agencies, increased demand will require commercial scale manufacturing. The value of disposable technologies continues to become more widely accepted in the contact manufacturing business as they are integrated into increasingly more manufacturing processes. While the requirements for a typical bioprocessing suite are well-defined and well-known, the design and construction of a contract manufacturing bioprocessing facility requires judgment based on limited experience, as in many cases we are dealing with emerging technology such as disposables. In this regard, contract manufacturing facility design provides challenges to the designer and builders that are many times more difficult to clearly define than a typical biopharmaceutical manufacturing facility.

Designers and builders need to be diagnostic and ask questions regarding time, flexibility, utilities, and space requirements. In response to these trends, contract manufacturing companies value facility design solutions that reduce capital requirements, increase production flexibility, reduce facility changeover time between products, and reduce risks. Emerging technology and innovation in facility design may lead to a biopharmaceutical production line placed in grey space in an open warehouse.

In the classic manufacturing facility, bioprocessing often requires dozens of separate unit operations, each involving many pieces of equipment. Processing equipment typically involves a significant investment. It can very often be a substantial obstacle for a contract manufacturing company. Flexibility and lower capital outlays are required by companies that perform quick product change-over. To minimize risk of cross-contamination, equipment is often dedicated to a single drug product, particularly at companies manufacturing multiple products. Disposable technologies offer the highest potential for contract manufacturing companies to meet their business requirements. With lower capital requirements and increased flexibility, disposables are an important part of risk management, facility strategy and service offerings.

Validation & Documentation

Production of pharmaceutical products through recombinant DNA in living organisms is a maturing technology under tight regulation, for patient safety. This regulatory environment requires thorough documentation of all pharmaceutical manufacturing processes, as well as complete documentation of manufacturing facility design and construction. Complete and thorough manufacturing production records would be kept in any facility, but pharmaceutical records are critical for production traceability. Biopharmaceutical manufacturing facility design is reviewed and documented at each stage of design, construction and startup, as part of the validation, or qualification process. These documentation reviews and executions are usually executed by specialized, independent validation contract firms, which carry a high implementation cost. Since every pharmaceutical product manufactured must be validated for production in its facility, some costs can be reduced through use of disposable, single-use bioprocess equipment components. These cost reductions are clearly advantageous for contract manufacturing facilities, as the contract manufacturer is committed to making many different products, each requiring independent facility production line validation.

When we consider that validation includes verification of process utilities such as oxygen gas and air for cell growth, heating and cooling supply for temperature control and monitoring instruments such as optical density for process control, it becomes apparent that validation activities are extensive and comprehensive. The clean steam source for equipment sterilization and Clean-in-Place (CIP) equipment for preparation, transfer and distribution of cleaning and rinse solutions for process equipment must also be validated, to ensure that the bioprocess equipment used in product manufacture is clean and sterile before each manufacturing use.

Using single-use disposable equipment components for some of the process steps in biopharm manufacture avoids sterilization validation and cleaning validation for those steps, which can have significant cost and schedule impact. Validation of process equipment cleaning is especially time-consuming because it requires verification that all process-contacting internal equipment surfaces have been cleaned, with residual process compounds removed and all cleaning detergents also rinsed and removed from those same internal surfaces. This can require analysis of both final cleaning rinses and sampling of the internal surfaces by “swabbing.” Internal surface swabbing may also be required to verify and document the elimination of all adventitious microbial bioburden following Steam-in-Place (SIP) sterilizations.

Single-Use Disposable Process Components

The simplest single-use disposable is the basic bag, holding a liquid volume appropriate for the process step. Although the concept is simple, being a stand-in for a polished stainless steel (SS) tank, the materials of which the bag is made are not simple, nor is the bag’s manufacture. The thermoplastic polymer films these disposable components are manufactured from are usually laminates of several different polymers, selected for resistance to gas permeation, tensile strength, chemical compatibility and resistance to liquid penetration, among other desired properties. After manufacture in low-particulate cleanroom environments, the assembled, sealed disposable components are sterilized, usually by gamma-source irradiation. The interior of the disposable is therefore clean and sterile upon delivery. From a validation standpoint, once the bag manufacturer is audited and identified as an approved vendor, and is released via internal quality standards, those components can be used in the manufacture of any pharmaceutical.

In preparation for licensure of the pharmaceutical product, the bag must be validated for the specific production process; this work is much simpler for disposables because much of the work is typically done by the vendor prior to launching the product. The advantage of the single-use disposable component thus becomes clear: validation is executed once, and need not be repeated for application of the validated components to the manufacture of other pharmaceutical products at the same facility. The reduction in validation requirements thus reduces both schedule and cost impacts on the project.

Fermentation/Cell Culture

Disposable single-use fermentation ‘bags’ are made by several manufacturers, in various sizes and configurations, up to a maximum of 1000 L. All the various configurations handle basic fermentation functions in different ways, depending on the configuration of the fermenter bag itself. For example, HyClone makes varying sizes (50, 100, 250 and 1000 L) of fermenter bags in a vertical 3:1 cylindrical shape designed to fit into their SS shell. The shell manages heat transfer with an electric blanket, or a jacket, contacting most of the bag external surface. Aeration is handled via sparge tubing with welded penetrations through the bag surface. Agitation is provided by a variable-speed drive top mounted on the support shell, fitting into an elastomer sleeve extending down to a propeller-style turbine. The sleeve penetrates the bag with a mechanical seal assembly that’s welded into the bag itself. Wave Biotech (GE Healthcare) makes fermenter bags from 1-1000 L in a flat configuration agitated by the rocking motion of the support table, with an oscillatory motion similar to a shaker table. The Wave reactor also handles aeration with sparge tubes welded into the bag.

Sartorius also manufactures a flat bag fermenter system using oscillatory agitation, under the Biostat Cultibag® name, in sizes from 1-2 L up to 200 L. There are also fermenter designs utilizing a rectangular solid bag shape, with penetrations for agitation and aeration similar to those described above. ATMI Life Sciences produces the disposable single-use Nucleo® cubical bag fermenter system with a top-mounted moving rod type agitator in 50 L and sizes up to 1000 L. The XDR® single-use bioreactor system from Xcellerex is another fermenter system using a support shell, with a magnetically coupled bottom-mounted agitator internal to the disposable bag. These systems are available between 10 L and 2000 L sizes.

Several sensor technologies are either in use, or under development, to measure temperature, dissolved oxygen (DO), pH, conductivity and osmolality. The most common technique utilized for measurement of temperature, DO and pH involve fittings that allow sensors to be autoclaved separately and subsequently attached to penetration adapter fittings welded into the fermenter bag. Single-use, membrane-based sensors have been developed that will allow these instruments to be incorporated directly into the fermenter bag (e.g., Fluorometrix Cellphase® sensors). Either fitting-based, autoclavable sensors, or membrane-based sensors connect to standard panel-mounted transmitters for control or monitoring purposes.

Clearly, a single-use disposable fermenter bag system is an expensive purchase, due to the intricacy of the agitation, aeration and instrumentation systems. However, a permanent fermenter installation is equally intricate, and very difficult to run CIP and SIP cycles on. CIP of intricate systems requires very involved validation protocols, especially when the CIP operations are completely automated.

Automated fermenter CIP is very complex because there are large numbers of double-block and bleed sanitary diaphragm valve clusters used in the sterile barrier assemblies surrounding the fermenter vessel. All of these sterile barrier entry ports into the fermenter must be both CIP’d and SIP’d. Cleaning validations for these complex systems are very involved and expensive.

Using single-use disposable fermenter bags has advantages other than extensive reductions in validation costs for CIP and SIP systems. For new manufacturing facilities dedicated to production of biopharmaceuticals, disposable fermenter bags represent a large reduction in capital facility installation costs: CIP and SIP systems are largely (although not completely) eliminated. The thermoplastic materials contacting the fermentation media also have the advantage that they contain no transition metal ions that can reduce cell viability and protein production rates. The Type 316 SS commonly used in permanently installed fermenter vessels contains nickel, chromium and iron, all of which have deleterious effects on living systems. The primary drawback to using disposable fermenter packages is their high operating cost.

Media Preparation

Similar reductions in validation costs can be achieved by employing single-use disposable bags in media preparation, rather than permanently installed SS tanks. The most common configuration for facilities using single-use bags in media prep has one or two conventional fixed SS tanks equipped with agitators and often, temperature control jackets. These fixed tanks are used to generate the media solutions, dissolving the required components in water for injection (WFI) or purified water (PW). Once the media is prepared, it can be transferred to a bag or bags for holding or for transfer to a fermenter.

The bag-mixing system is frequently an open-top container, intended to line a cylindrical or rectangular holder. The mixing agitator assembly can be magnetically-coupled across the bag surface, or mounted externally. Mixing bags with agitation systems are available from several suppliers. HyClone’s Single-Use Mixer (S.U.M.) is one example, applying the 100 to 1000 L single-use disposable bag technology described earlier to solution preparation and mixing, again with a top mounted agitator in the bag. HyClone also produces a disposable solids bag, or PowderTainer®, that can be coupled to the S.U.M. for transfer into the solution preparation bag.

There are several similar systems offered by several manufacturers. ATMI Life Sciences makes a mixing bag system with their WandMixer® top-mounted design in a rectangular bag, between 5 – 200 L volumes. ATMI also has a bottom mounted magnetic drive agitation cylindrical bag system, the Lev-Tech®, in volumes from 30 L to 2000 L. Millipore’s Mobius® (originally Newport Biosystems) cylindrical mixing system also uses a bottom-mounted magnetic drive agitator, in volumes as large as 3500 L. Wave Biotech’s (GE Healthcare) Wave Mixer uses the flat bag oscillating table technology from its fermenter system in a mixer configuration between 20 – 1000L volumes. Xcellerex uses a bottom-mounted magnetic drive agitator in its cylindrical XDM-100® and -200 mixing systems. Stedim (Sartorius) makes the rectangular Flexel® mixing bag system, also with a bottom-mounted agitator from 100 – 1000 L capacities.

Typically, cost savings from disposables used in manufacturing facility design are best achieved by designing the facility for use of bag(s), rather than using the bags to replace or supplant existing fixed SS tankage.

Packaged media components are also available from many suppliers. HyClone provides various grades of both media, dry and in solution. Other manufacturers also produce dry media preparation kits.

Buffer Preparation

The discussion of the media prep function in the immediately preceding paragraphs is also applicable to the buffer preparation area supporting product purification. Buffers would support sequential processing in any one of several process unit operations. All of the single-use disposable mixing systems noted in the preceding section are also used in buffer preparation.

Single-use disposable bags rather than permanent fixed tanks reduce the fixed piping infrastructure needed for CIP, SIP and buffer transfer operations. Validation requirements would also be reduced, based on the discussions above.

Liquid Transfer

Movement of media or buffers into and out of disposable bag reservoirs in a sterile fashion is a design issue of major concern. To date, this has been handled using the tubing welded into the bag shell for filling or draining. Tubing welders can be used to make sterile joints between separate tubing connections. These welders use a heated, sharp-edged blade to trim the joint surfaces and weld the trimmed ends together, with blade temperatures on the order of 200ºC sterilizing the welded tube ends. Tubing welders are available from a number of suppliers, including Sartorius, Wave Biotech and Terumo. This technique can also be used to sample process fluids aseptically, without the need to draw liquids out of the reservoir into a non-sterile environment.

Alternative connection methods involve autoclavable tube sets, tube assemblies or connection systems, or require connections to be made under laminar-flow hoods.

Purification

Single-use disposable bags holding buffers can be used to support chromatography column(s) in either bind-and-elute or flow-through mode, tangential flow filtration across membrane cassettes in ultrafiltration (UF) or diafiltration (DF) buffer replacement mode, or other process unit operations. Conceptually, these disposable components serve as buffer reservoirs feeding either conventional multi-use skid mounted process equipment. However, there are several newer disposable technologies on the market today, applicable to unit operations from clarification to membrane filtration and chromatography.

Depending upon the availability of components and the sophistication of a given biopharmaceutical manufacturer’s production processes, a mixture of chromatography and tangential flow filtration (TFF) membrane filtration process skids may be integrated into a manufacturing facility using disposable single-use components.

Filter Capsules

Bioprocess industry suppliers provide disposable cartridges or modules for dead-end normal filtration. These single-use filter elements come in a commonly used capsule format for dead-end filtration or gas filtration, with the filter element enclosed in an integral disposable polymeric housing. Millipore, Pall, Sartorius, CUNO, GE Healthcare, Meissner and others all provide ranges of ‘dead-end’ or ‘normal’ filter capsules for both gas filtration (i.e., venting, gas blanketing, aeration, oxygenation) and liquid filtration (i.e., clarification, virus filtration, particulate removal).

Clarification – Depth Filtration

Classically, clarification used large pressurized depth filtration housings holding stacked lenticular filter support media with filtration aids (e.g., diatomaceous earth). Disposable single-use filter capsules are currently available for a wide range of specialized filtration applications. CUNO Corp., maker of some of the earlier depth filtration systems, markets the Zeta Plus® disposable single-use cartridge filter series, various permutations of which include membrane-enclosed depth filtration media, or various adsorbent media such as activated carbon or lipid-specific adsorbent. (Lipid removal capability can assist in maintaining flow capacity across 0.2μ sterilizing filters.) Pall Corp.’s series of SupraCap capsule depth filters are also available for the clarification unit operation. Sartorius’ Sartoclear P MaxiCap® line of disposable depth filter capsules can also be applied in this niche, as can Meissner’s UltraCap H.D. All of these systems employ an integrated polymeric housing containing the filtration medium (usually cellulosic, but others as well) within. Although these single-use disposable filter capsules are discussed here in the Purification section, these capsule systems are often employed in harvest operations, where they perform very effectively.

There are also single-use process filters fabricated in cassette format with a holder frame, similar to a membrane filter; Millipore’s Millistak+® Pod filter is an example of this type process filter, with varying filtration media capability and several different module sizes available. The Pod filter’s wetted surfaces are single-use disposables.

Chromatography

Since the chromatography column feed preparation system’s many functions and instrument sensors were rather intricate, making it disposable presents somewhat of a challenge. GE Healthcare has made the chromatography resin and column fllowpaths into a single membrane-enclosed capsule, called the ReadyToProcess column, available in three sizes, from 2.5 L to 10 L volumes. These single-use disposable chromatography column capsules mate to a much simplified preparation system that GE Healthcare calls the AKTAready® system, which operates under the familiar “Unicorn” chromatography system control software.

Sartorius manufactures Sartobind MultiSep cartridges, which can serve as ion exchange or affinity chromatography unit operations. These cartridges can be single-use disposables or can be re-used; these are relatively small-scale devices.

Membrane Filtration

GE Healthcare makes a range of single use disposable hollow fiber membrane cartridges, up to the 300 ft2 ProCell cartridge. These cartridges can be integrated with a flow system skid GE calls Uniflux, which generally has T316 SS components that tend not to be disposable.

Other manufacturers are investigating the single-use market as well, but most membrane filtration systems at larger scale are still ‘permanent’ in the sense that development efforts are ongoing to produce operable unit operations with disposable single-use components.

Disposables and the Contract Manufacturer

As discussed above, single-use disposable process components are becoming available that can handle almost all commonly used unit operations from media and buffer preparation to fermentation, harvest, purification and bulk formulation. These disposables offer many advantages to manufacturers producing multiple products, such as reduced capital costs, reduced piping infrastructure costs, especially for CIP and SIP distribution. Disposables also reduce validation costs through elimination of fixed equipment installations, with the accompanying CIP and SIP requirements. Additionally, the facility floor space requirements for many operations with single-use disposable components are often smaller than permanently installed equipment.

Given that each product-contacting operation employing single-use disposable components no longer requires cleaning and sterilization operations, it is easy to see that facilities producing multiple products would also enjoy the large advantage of no cross-contamination among products, since any product contact surfaces in the disposables are replaced after each processing step. Thus, the contract manufacturer that produces many and varied pharmaceutical products can achieve both significant cost savings and added safety by employing single-use disposable components in the production facility.

Tony Garbarino is Regional Manager, Northern California for Harris Group Inc., an engineering firm with more than 18 years of experience in the biopharmaceutical industry. Dave Odegaard is a process engineer with Harris Group.