20tips purchasing bio reactor

8/6/2019 20Tips Purchasing Bio Reactor

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52 BioPharm SEPTEMBER 1996

Choosing laboratory fermentors and cell

culture bioreactors can be a complex matter.

It usually requires experience and technical

expertise to fully comprehend the

specifications and engineering nuances ofvarious competitive fermentors. A major

problem lies in the lack of specific

information required to make intelligent

decisions. For various reasons,

Julia Cino and Stanley Frey

Tips for Purchasing

Research Fermentorsand BioreactorsA Practical Guide for

Researchers

TECHNICAL NOTETECHNICAL NOTE

Julia Cinois product manager, and corresponding

authorStanley Freyis director of advertising at

New Brunswick Scientific Co., Inc., P.O. Box 4005,

44 Talmadge Road, Edison, NJ, 08818-4005, (800)631-5417, fax (908) 287-4222, [email protected]

In this three-part series, the authors provide a practical guide for

purchasing research fermentors and bioreactors. Part 1 describes five

ways to avoid making costly mistakes. Look for the remaining 15 tips in

upcoming issues of BioPharm.

Q Which types of glass vessels will shorten sterilization andcool-down cycles rather than prolong them?

Q Which glass vessels are more vulnerable to breakage?

Q Can glass vessels be safely steam-sterilized in place?

Q Are threaded ports in the fermentor headplate designed tocompletely eliminate the risk of contamination?

Q Which stainless steel surface treatments are FDAvalidatable?

Q Are all mirror-finished stainless steel vessels free ofunsanitary microscopic crevices?

Q How can you be sure the reactor is capable of rapid heat-upand cool-down?

Q Are filters supplied for the fermentor but completelyoverlooked for addition vessels and accessory ports?

Q Will prefiltration and regulation of air and water services benecessary for dependable operation?

Q Does the culture system have the capacity to deliver a

sufficient supply of oxygen to meet the demand ofhighly aerobic organisms?

Q Will you be able to perform temperature induction studies withyour new equipment?

Q Are analog or digital systems more reliable?

Q Will your new fermentor be able to communicate with yourexisting recorders and controllers?

Q Can the system maintain the desired temperature and rate ofagitation while overcoming the added heat load and viscosity

of densely growing organisms?

Q Will you receive start-up assistance and after-sale supportfor your bioprocessing software?

ASK THE RIGHT QUESTIONS

manufacturers often omit critical product

specifications and performance data from

product literature or formal quotations.

Some may not have the research facilities or

technical staff to conduct the required

performance tests, and others may be

reluctant to reveal unfavorable data thatmight impede sales. Whatever the reason,

this omission can leave a gaping hole in

your information-gathering process.

In purchasing fermentors and reactors

you must address vessel design and

sterilization problems. Consider questions of

mass transfer capability, bacterial

contamination, and FDA validation

requirements. Knowing which design

features to look for and the right questions toask can take the mystery out of the decision-

making process and keep you from makingcostly mistakes. (See Ask the Right

Questions box.)

With so much at stake, it is imperative

that you ask critical questions and receive

meaningful answers. Asking the right

questions can help you cut through the veil

of confusion and correctly assess the

advantages and disadvantages of the

products available. Equipment

manufacturers can have significantly

different design and fabrication standards.

Users needs also differ. Some may requireonly a simple fermentor, whereas others,

because of budgetary constraints, may invest

in only a bare bones culture vessel. For users

with more sophisticated research or specific

20


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vessel beneath a stainless steel headplate.

Upon removal of the fermentors from the

autoclave, the medium in the first two

reactors appeared normal. However,

investigators were uncertain about the

sterility of the medium in the glass-jacketed

vessel. Acting as a thermal insulator, the airspace in the glass-jacketed fermentor

impedes the flow of heat to the medium,

preventing it from reaching the required

temperature in the expected time.

According to heat flow studies

(conducted by New Brunswick principal

investigator Y. Chen at Rutgers University

in 1996) with stirred jar fermentors in an

AMSCO Scientific (Apex, NC) Model 72A

wall-mounted autoclave, the stainlesssteeljacketed fermentor reached

sterilization temperature in less than half thetime of the glass-jacketed fermentor. With

thermocouples immersed in the culture

medium of each vessel, the medium in a 5-L

Type B fermentor reached 121 C in 35

minutes, compared with the glass-jacketed

fermentor, which was unable to reach

121 C even after 90 minutes (Table 1). A

similar problem occurs during the cool-

down cycle. Vessel Type C requires a much

longer cooling time because of the slower

transfer of heat through the air space in the

glass jacket.To remedy those problems, some

researchers fill the glass jacket with water to

speed up heat transfer. Unfortunately, when

the jacket of a 5-L fermentor is filled with

11.4 L of water and then autoclaved, tests

show that it takes 55 minutes to attain a

Can glass jar fermentors be safely steam-

sterilized in place? As far as can be

determined, sterilization in place of glass

fermentors and bioreactors involves some

risk if you select the wrong system.

Laboratory culture vessels can withstand

repeated sterilization in an autoclave

because vessels are vented, which equalizes

the pressure inside and outside the vessel.

But if the pressure inside the vessel

becomes greater than the pressure outside(as occurs when pressurized steam or gas is


process needs, a simplified system may not

be enough. Whatever your needs, weve

identifed 20 ways to avoid making common

and costly mistakes when purchasing

fermentors and bioreactors. Here are five of

them.

Temperature control can sometimes go awry

over the course of a fermentation in which

high concentrations of biomass areproduced, especially when glass-jacketed

reactors are selected as the culture vessel.

Glass is a poor conductor of heat and has

approximately one-fortieth the heat-transfer

capability of stainless steel (1). The

exothermic reaction of cultures growing at

densities of 50 to 100 grams per liter can

overwhelm temperature control in glass-

jacketed vessels. At ambient temperatures,

circulating cold water in the jacket is notalways enough to compensate for the heat

output of high-density cell growth. Duringexponential growth, insufficient cooling

capacity causes operating temperatures to

rise significantly above the set point.

This problem also surfaces during the

sterilization cycle because glass limits the

heat-exchange capacity of the vessel. The

gravity of this problem was clearly

demonstrated during a fermentation

workshop in which three different types of

laboratory fermentors were simultaneously

autoclaved with the same medium in the

same autoclave. Fermentor vessel Type Awas a conventional flat-bottom glass jar with

a stainless steel headplate (Figure 1). Vessel

Type B was a cylindrical glass tube mounted

between a stainless steel headplate and a

dished-bottom jacket of stainless steel.

Vessel Type C was an all-glass jacketed

1 Choose the right vessel for yourprocess.

2 Know the risks of steam-in-placeglass fermentors.

3 Avoid mishandling glass fermentorsduring sterilization.

4 Beware of unsanitary threads andfittings.

5 Know which surface finishes andtreatments are FDA validatable.

6 Demand proof of performance.

7 Avoid glass condensers.

8 Know whether manfacturer paysfor prefilter kits for air, water, andsteam.

9 Is your system designed fortemperature induction?

10 Specify unbreakable side-wall

vessel ports.11 Compare analog with digital

controllers.

12 Make sure the new fermentationsystem communicates with yourexisting instrumentation.

13 Make sure you get all the parts andpieces you need.

14 Know what instruments areincluded in the manufacturersquote.

15 Determine your long-termrequirements for feeding additives.

16 Ask the manufacturer about itsFDA validation package.

17 Know who will service your systemand where.

18 Use your PC to its fullest extent.

19 Ask about start-up assistance andservice agreements.

20 Make sure your system can producethe required dissolved oxygenconcentration.

20 TIPS FOR PURCHASING

1 Choose the Right Vesselfor Your Process

2 Know the Risks of Steam-

in-Place Glass Fermentors

fed directly into the glass jar), the glass whether borosilicate or Pyrex can crack

or burst. Such danger applies primarily toglass jar vessels (Type A), which are

vulnerable to breakage, especially where the

base is joined to the tubular walls. On the

other hand, Type B vessels are less sus-

ceptible to breakage because the number of

stress points is significantly reduced by the

tubular design of the glass vessel (Figure 2).

Do not be misguided by a pressure gauge

or pressure-relief valve mounted in the

vessel headplate. It offers no protection

against the stress placed on glass that can

burst at pressures below 5 psig. For thisreason it is unsafe to pressurize a glass


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for a jacket that is open and flanged at the

bottom where it is sealed against a

protective steel baseplate. This adds little or

no extra cost to the vessel and provides the

convenience of good visibility and

protection against glass breakage.

BioPharm SEPTEMBER 1996 55

sterilization temperature of 121 C a

heat-up time that can result in excessive heat

exposure and high turbidity for some media.

Avoid a glass jacket that is permanently

closed, because the jacket interior cannot be

cleaned of debris and condensation. Look

Vessel Size Maximum Sterilization Jacket WaterFermentor Type (liters) Temperature (C) Time (min) (liters)

Cylindrical glass tubewith dished stainless steel

jacket (Type B) 5 121 35 None

All-glass jacketed 7.5 119 90 Nonevessel 5.0 121 55 1.0(Type C) 2.2 121 55 1.4

Table 1. Sterilization of bioreactors.

A B C

lass ar lass ermentor

uick-con ect

p

Gla s b r tor

p

Unbreakableside p r s

. .

ll-glass jacketed

G ss h seb rb ( t r

nle p r )

Gl s b rb a e o let p r )

Glass jacket

Figure 1. Fermentor vessels. Type A: Flat-bottom glass jar with stainless steel headplate. Type B: Cylindrical glass tube mounted

between stainless steel headplate and dished-bottom jacket and baseplate. Type C: All-glass jacketed vessel mounted beneath

stainless steel headplate.

Figure 2. Avoid accidental spills in steam-in-

place glass jar fermentors by ensuring that

your fermentor is protected by a

pressurizable dome that is anchored

securely over the glass vessel during

sterilization. Shown here is a pressurizabledome of stainless steel that clamps

securely to the base of the fermentor.

protection against glass breakage, they offerlittle or no protection against hot medium

spills. Unless internal and external pressuresare equal during sterilization, and unless the

glass vessel is completely protected by a

pressurizable steel safety hood, in situ

sterilization of glass jar fermentors is not

recommended.

Knowing the configuration and surface

area of the jacket or cooling coil is

insufficient to evaluate the heat transfer

efficiency of the reactor. To determine

whether a reactor design can meet the

heating and cooling requirements for a

particular process, investigators must knowthe heat output of the culture at maximum

cell density. Place that responsibility with

the vendor by specifying the heat-removal

capability of the equipment, expressed in

watts per liter. Find out before you buy

whether temperature can be maintained with

the circulation of city water (at the citys

highest lab temperature) or whether the

vendor requires an expensive accessory

chiller system to meet your lowesttemperature requirement.

reactor in the open environment of theworkplace.

At high temperatures and pressures, glasscan break at weak stress areas where glass

thickness varies. Such differences in

thickness can vary as much as 6 mm. Such

variations can cause multiple stress points

that are vulnerable to damage during

sterilization. Stress on the glass is

exacerbated by the added tension resulting

from different expansion coefficients of

metal and glass.

Several fermentor manufacturers offer an

inexpensive sterilization shroud designed to

contain accidental glass breakage duringsterilization. Although some shrouds afford


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It is commonly known that special care must

be exercised in autoclaving an all-glass

vessel or reactor, but accidental breakage

during sterilization and handling still occurs.A mistake of this type can be costly

Figure 3. Ensure that your steam-in-place

fermentor can be completely sterilized in

place. Allow for the simultaneous

sterilization of accessories, such as

addition vessels, feed lines, and filters as

illustrated.

3Avoid Mishandling GlassFermentors duringSterilization

5Know Which SurfaceFinishes and Treatmentsare FDA Validatable

To satisfy FDA validation requirements, all

internal welds must be ground and polishedso that no corners and crevices remain

where contaminants could possibly lodge.

Such a finish is achieved by first

mechanically polishing the interior surface

to a 20-micro-inch roughness average (Ra),

followed by electropolishing and

passivation. (Exterior surfaces need be

polished only to a 35-micro-inch Ra to

facilitate cleaning.) Electropolishing is an

electrolytic dissolution of the metal surfaceprojections, which smooths and brightens

the surface. Passivation is a final step thatconstitutes soaking the fermentor in a

caustic solution followed by a nitric acid

bath that cleans the metal and creates a

chemically inactive surface that is highly

resistant to corrosion.

All that glitters is not gold. So it is with

process vessels. A highly polished mirror

finish does not necessarily mean that the

stainless steel surfaces are smooth and

sanitary. Such bright finishes are deceptive

when they are applied over poorly ground

surfaces to conceal an unsanitary finish. Anelectropolished finish is more sanitary than

mechanical polishing, which can leave

microscopic crevices that trap particulate

matter. Not all equipment is manufactured to

these standards. Some are mechanically

polished and then passivated, bypassing the

electropolishing step. Most laboratories

accept this standard, but to ensure that you

get what you want, these requirements

should be clearly defined in yourspecifications.

4 Beware of Unsanitary Threads and Fittings

fabricate but are not universally accepted.

Avoid ports with internal threads if your

equipment must comply with FDArequirements. Unfortunately, in small-size

vessels this construction consumes muchneeded head space and does not allow for a

full range of sanitary welded ports.

O rings can prevent almost all potential

contamination in laboratory and pilot plant

environments. But set screws used to anchor

impeller blades to an agitator drive can

present some risk if they are not carefully

washed and cleaned. Submerged in liquid,

these screws are sterilized with the vessel

and are not typically exposed to airborne

contamination.

Every opening in the fermentor should be

designed and constructed for maximum

protection against contamination. If

headplate ports and penetrations haveinternal threads, ensure that they are sealed

with O rings so that the threads are notexposed to the process side of the reactor.

Threads are difficult to clean and can harbor

contaminants in tiny crevices where bacteria

are not easily destroyed by sterilization.

An average reactor vessel contains at

least 10 openings in the headplate, each a

potential risk of contamination. Many

buyers insist that ports be welded to the

headplate wherever possible so that the

threads can be located on the outer perimeter

of the port and unexposed to the process.

Ports with internal threads are cheaper to

from $450 to more than $1,000 for a 5-L

replacement vessel, depending on its country

of origin. A frequent mistake is to remove

the vessel from the autoclave too early.

Make sure that the autoclave is properly

vented during sterilization and that the

vessel is removed only after it has cooled forthe length of time specified by the

manufacturer.

Unless your lab personnel are able to

carry heavily laden, 10-L (and greater) glass

fermentors, avoid purchasing large-volume

glass reactors. When a heated reactor is

removed from the autoclave, the tensile

strength of the glass is significantly

weakened and is highly vulnerable to

breakage.Many SIP benchtop fermentors, whether

made of glass or stainless steel, cannot besterilized in their entirety. Accessory

syringes, connectors, samplers, reservoirs,

and transfer tubing for acid, base, and

antifoam must be autoclaved separately and

then aseptically connected after sterilization.

There is little advantage to an in-place

sterilization system if an operator must carry

the accessories to an autoclave and then

sterilize them separately. If an SIP system is

complete and your system has sufficient

capacity to accommodate the sterilization of

accessories, you can avoid time-consumingtrips to the autoclave (Figure 3).

Looking Ahead

Part 2 of this three-part series continues with

more tips for purchasing research fermentors

and bioreactors.

References(1) J.M. Coulson and J.F. Richardson, Thermal

Conductivities, Chemical Engineering,Vol. 1: Fluid Flow, Heat Transfer, and MassTransfer, J.R. Backhurst and J.H. Harker, Eds.(Pergamon Press, Oxford, UK, 1977), 174. BP


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TECHNICAL NOTE

42 BioPharm SHOWCASE FEBRUARY 1997

Julia Cino and Stanley Frey

Tips for Purchasing ResearchFermentors and Bioreactors

A Practical Guide for Researchers, Part 2

This concludes a two-part guide for purchasing research fermentors and bioreactors.

Part 1 included tips 1 through 5 and appeared in the September 1996 issue of BioPharm.20Exhaust gas condensers protrude from the headplate and

can be easily broken if made of glass. A stainless steel

condenser can be much more expensive, but it is unbreak-able and a superior heat exchanger more efficient at con-

densing the exhaust gases lost in evaporation and return-

ing them to the culture (Figure 2). In addition, avoid the

simple cold finger (tube-within-a-tube design). To max-

imize heat-exchange capability in the condenser, a turbu-

lent flow of gas is required. One way to improve heat-exchange efficiency is to pass exhaust gases in a tortuous

path around an inner cooling coil for vigorous mixing and

enhanced contact with the surfaces of the cooling coil.

xh ust

r n oress l

ool i g oil

o erla e

oldwa erin o t

Figure 2. To avoid increased viscosity of the culture

medium over time, your bioprocessing system

should be equipped with an exhaust gas con-

denser to minimize evaporation loss. Determine

whether the device is made of glass or stainless

steel and whether it is designed to create a turbu-

lent flow of gas for enhanced heat transfer.

Julia Cinois product manager, and corresponding author

Stanley Freyis director of advertising at New Brunswick Scientific

Co., Inc., P.O. Box 4005, 44 Talmadge Road, Edison, NJ, 08818-4005,

(800) 631-5417, fax (908) 287-4222, email ([email protected]).

Before you buy a steam-in-place (SIP) fermentor or bioreac-

tor, ascertain how long the system takes to complete steril-

ization and cool-down cycles. Dont wait until the equip-

ment has been delivered to learn that there is an unexpected-

ly long delay in reaching sterilization and cool-down

temperatures.

Some systems allow users to select heat-up time as well

as the sterilization period a feature that is particularlyuseful in mimicking heat-up times for very large fermentors.

To discover bacteriological leaks or performance prob-

lems in a fermentation system before shipment, manufactur-

ers of SIP fermentors usually conduct a 48- to 72-hour

sterility test in which the heat-up and cool-down tempera-

tures are recorded (Figure 1). If this record is not included in

the standard documentation package, ask for it in the pur-

chase order. In addition to revealing sterilization and cool-

down times of the vessel contents, records should tell youwhether growth temperature can be maintained within the

levels of accuracy specified in the

manufacturers literature andwhether the system is properly engi-

neered for rapid heat-up and cool-

down. This information should be

readily available from the manufac-

turer.

The system should be designed

for cool-down after sterilization by

water circulation. For non-SIP ves-

sels, manufacturers should provide

information about the time required

to reach sterilization temperature (of

water) at maximum working

volume.If conserving water is a consider-

ation, the fermentor should be

designed for continuous recircula-

tion of chilled water. To avoid dis-

posing water down the drain, the

system should be fabricated with a

water jacket or a cooling coil in con-

junction with an accessory chiller

that recycles coolant back to the

fermentor.

6Demand Proof of Performance

a)

b)

0:

5

5.0

0.0

2 .0

1 :00 36:00

Ti e (hr)

5 : :

0:

5 0

0

50.0

25.0

00: 0 0 :00

Time (hr)

01: 0 :

Figure 1. Manufacturers 72-hour sterility test of a steam-in-place 20-L benchtop

fermentor in which key operating parameters including pH and dissolved oxygen

(DO) are recorded (not shown in temperature profile). Profile (a) plots the heat-

up and cool-down time from ambient to 125 C over a 72-hour period. Profile (b)

displays greater detail in an expanded scale of a two-hour segment of the sterility

test.

7Avoid Glass Condensers

TECHNICAL NOTE

1 Choose the right vessel for your process.

2 Know the risks of steam-in-place glass fermentors.

3 Avoid mishandling glass fermentors during sterilization.4 Beware of unsanitary threads and fittings.

5 Know which surface finishes and treatments are FDA validatable.

TIPS FOR PURCHASING 1 through 5


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Buyers often forget to ask about installation and connec-

tion of equipment to air, water, and steam facilities.

Remember to allocate funds for prefiltering and regulating

those services if necessary (Figure 3).If particulate matter is not removed from water, air, and

steam supplies, it can accumulate as sediment in solenoid

valves. There it can cause the valve plunger to freeze in

place or prevent the valve seat from properly sealing

against the plunger. Such deposits can strike a damaging

blow to temperature control systems when cold or warm

water fails to circulate or shut off on demand. In addition,

water and air supply lines may be highly pressurized and

can rupture filters if not controlled by in-line pressure reg-ulators.

Know which manufacturers include these preassembled

piping assemblies in their price and which do not. Some

state and local licensing laws prohibit out-of-state manu-

facturers from making the necessary piping connections in

a research facility, so some manufacturers are unconcerned

with the connection of equipment to utilities. A single pre-filtration and regulation hook-up can often be adapted for

more than one bioprocessing system. Before these compo-

nents are installed, ask your building superintendent

whether the piping is needed. Then make sure your water,

steam, and air services are adequate for the system you

intend to purchase.

Ste pre i ltersembly

A r preiltersem ly

ly

Figure 3. Because piping connections to utilities that regu-

late and prefilter steam, air, and water are not always

required, these connections can be overlooked by the

seller.

Temperature induction can be an effective tool for expres-

sing many important proteins. A temperature shift can be

performed manually or automatically with computer soft-ware that allows you to establish a time-driven table of

temperature set points. But if the system hardware is not

designed for rapid heating, it may be difficult to control.This is purely a function of the heat-exchange system,

which should provide a sufficiently large surface area to

heat the maximum volume of culture at a rate of not less

than 1 C per minute over a range of approximately

3242 C (1).

Temperature shifting has been used with many cell lines

to increase product yield. A hot finger is an inexpensive

approach to the problem but is not always the best choice,

especially for propagating highly aerobic organisms or in

those applications where temperature of the water supply is

a desired temperature for the process.

9Is Your System Designed forTemperature Induction?

With laboratory bioprocessing equipment, avoid purchas-

ing glass vessels with breakable glass process ports (ser-

rated hose connections) that project from side walls.

Broken glass connectors are inevitable and usually necessi-

tate replacing the entire vessel. Polymeric connectors are

autoclavable and seldom, if ever, break. Ensure that con-

nectors are removable and designed to be replaced or

plugged up.

10 Specify Unbreakable Side-WallVessel Ports

Dont be misled by analog equipment of the past dressed

up with modern digital displays for temperature, speed, and

other parameters. With analog instruments, zero andspan are interactive and therefore difficult to calibrate

accurately. Accordingly, they may display erroneous read-

ings for values measured over an entire control span. Avoid

analog systems with signals that are fed to a signal proces-

sor located centrally in a facility. With analog systems, a

bundle of 20 or more wires can extend over long distances

where signals can be easily corrupted by spurious impulses

or electronic noise generated in the facility. Digital sys-

tems are more reliable with no more than four wiresrequired to transmit the data contained on all loops

combined.

If your system is digitally controlled, signals can be

optically isolated and protected against ground loops.

Signal conditioning takes place on a signal-conditioning

card or mother board mounted at the console where all ana-

log signals are converted to digital.

11 Compare Analog with DigitalControllers

Dont paint yourself into a corner by ordering a new analog

fermentor that is incompatible with the digital recorders and

controllers currently in your laboratory. Dont wait until itstoo late to find out that the new bioreactor you purchased

cannot communicate with your PC. Coupling an analog-to-

digital and digital-to-analog converter to the system allowsall types of equipment to interface with each other (Figure

4). This electronic converter should be capable of changing

digital signals into 4-20 mA signals used by analog equip-

ment. If the converter can change 4-20 mA signals into an

RS-232 or RS-422 format, then the equipment will be com-

patible with computer software for data logging and pro-

grammed control.

12 Make Sure the New Fermentation System Communicates withYour Existing Instrumentation

Figure 4. Your new equipment should be compatible with

the equipment currently in your facility. If its not, a univer-

sal converter can be used to talk to both analog and digi-

tal instrumentation.

Most automatic addition systems contain a dozen differentparts including the control module. Check your foam control

system, for example. Make sure yours is equipped with more

than a sensor, a controller, and an addition pump. Does the

reactor have an antifoam addition line preinstalled in the head-

plate, or must you remember to order it separately? Is the sys-

tem available with a sterilizable antifoam reservoir with a trans-

fer line, tubing, and a filtered exhaust outlet? Some scientists

object to hunting down all the bits and pieces needed to assem-

ble a complete system. You can spend thousands of dollars for

a complete bioprocessing system. You shouldnt have to rum-

mage through your supply closets and benches for $20 worth of

attachments.

Depending on the price, some equipment can total the num-

ber of antifoam addition cycles, allowing you to calculate the

cumulative volume of chemical defoamer and other supple-

ments that may be added to the culture. With the appropriate

computer software, the total volume of all additives can be cal-culated for you. Just punch in the volume per dose at the incep-

tion to determine the total volume of any supplement at any

time during the process. Such on-line measurements can help to

instantly evaluate the influence of additives on productivity.

Ask the seller whether the foam sensor can be used inter-

changeably to detect foam and liquid levels. If the metering

pump can be electronically assigned and programmed for dif-

ferent functions, the added flexibility can sometimes be useful

for liquid level control when it is necessary to add supplements

to the culture vessel.

If you order an SIP system, ensure that it meets your

requirements for the aseptic addition of biological materials. If

your process calls for repetitive sampling and addition of

reagents, you may require resterilizable addition and sampling

ports that allow you to steam the inlet and outlet lines before

and after each operation.

13 Make Sure You Get All the Parts and Pieces You Need

8 Know Whether Manufacturer Pays for Prefilter Kits for Air, Water, and Steam


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Of all the mistakes made in purchasing bioprocessing equipment, underusing the computer that

controls the process may be the most serious. Most bioengineers using PCs in fermentation and

cell culture use their computers primarily as data loggers. Analysis of computer software appli-

cations in the bioprocessing field reveals that only 15% of researchers use computers as

process development tools. Paradoxically, the computer technology that helped us discover a

path to the planets in space exploration is used merely as a recorder in the discovery of biolog-

ical products. There is some economic justification for this. A single PC with specialized soft-

ware can monitor eight processes simultaneously at a cost of approximately $800 per process.This amounts to a saving of over $6,000 for six-point recorders that have no programmable

control and no on-line accessibility to historical data.

Nonetheless, we have at our disposal an indispensable tool in the computer that can opti-

mize yields and reduce R&D time. To satisfy the metabolic demands of microbial cultures,

computer control strategies can be employed for parameters, such as nutrient feeding, dis-

solved oxygen, and oxygen supplementation. Without requiring algorithms or equation-writing

skills, operating conditions can be changed as a function of time or of any measured or calcu-

lated variable, such as cell density, protein concentration, and dissolved oxygen.

With a few clicks of the mouse an investigator can change a digital readout of dissolvedoxygen to an X-Y plot of that parameter, displaying a complete record of dissolved oxygen

over time. With two more clicks of the mouse, X-Y plots of protein production and agitation

can be superimposed over dissolved oxygen in a single chart to elucidate the interaction of all

three parameters.

Because of the proprietary nature of their work, some laboratories may be reluctant to con-

sult with software manufacturers about manipulating the computer for yield improvement.

However, many researchers who do use the computer to control the fermentation process havemade significant advances in process development.

In a feasibility study conducted at New Brunswick Scientific Co., Inc., researchers used a

computer to design a nutrient feeding program and dissolved oxygen strategy for a fed-batch

fermentation with continuous perfusion. Cell yields increased from 40 to 200 g/L (dry weight),

and protein concentrations increased from 30 to 300 mg/L (3).

If biochemical engineers are to make important progress in scientific research the computermust do more than store, retrieve, and display data. Scientists need to explore the many paths

to increased cell growth and protein production. Instrument makers and the research communi-

ty must cooperate more closely if they are to use the great potential of cybernetics in scientific

research (Figure 7).

18 Use Your PC to Its Fullest Extent

Figure 7. With currently available software programs, operators can produce a minute-by-

minute panorama of the complete process, observing on-line graphic displays of up to

24 parameters as well as interactions between variables.

Find out who will service your new equipment and where

the service center is located. If service is not performed onsite, equipment may need to be crated for return shipment to

the factory. This is time-consuming and risky in terms of

properly packaging equipment for transit. If service is per-

formed at the vendors repair shop, then determine who is

responsible for the crating, shipping, and insurance costs.

If the equipment is sold and serviced by a major labora-

tory supply house, chances are good that the company will

be around to deliver the support you need. Find out whether

the service center has a large inventory of spare parts and

how long it will take for parts to reach you.

19 Know Who Will Service Your

System and Where

To ensure that your new bioprocessing system is properly

installed and operates efficiently, you and your staff shouldreceive start-up assistance and training at your facility. The

procedures involved in sterilizing, preparing, calibrating,

and installing sensors and other ancillary equipment and

instrumentation are vital to the success of your project, and

the cost of conducting those procedures should be included

in the price of the equipment. If the equipment fails to meet

performance specifications, this is the time to find out.

20 Ask About Start-Up Assistance

and Service Agreements

Learn from the Mistakes of Others

Instrument makers are not known for volunteering detailed

information about the products they manufacture.Sometimes it takes determination to get to all the facts.

Unlike automobile companies who drown their consumers

with information, technical data published by equipmentmanufacturers is frequently sparse. In the field of biotech-

nology, product quality does not come under the scrutiny of

consumer protection agencies or the critical voice of the

media. In the absence of a well-informed purchasing author-

ity to help make important choices, researchers must be pre-

pared to question product performance as well as a manu-

facturers credibility. For buyers with limited knowledge

and practical experience in purchasing fermentation equip-

ment, this guide is of particular value. Buyers with an engi-

neering background and experience with fermentation or

cell culture may be better equipped to find the best products

at the best price. But even those with the know-how and

experience can benefit from the mistakes of others.

References(1) Y. Chen et al., Production of Plasminogen Activator Inhibitor-

Type-1 (PAI-1) in anE. coli Fermentation Process, paper pre-sented to the Ninth Symposium of the Protein Society, Boston,1995.

(2) J. Voss, Cleaning and Cleaning Validation: A BiotechnologyPerspective, J. Voss, Ed. (Parenteral Drug Association, Bethesda,MD, 1996), 148.

(3) Y. Chen et al., High Protein Expression Fermentation ofRecombinant Pichia pastoris in Fed-Batch Process, unpublishedpaper, New Brunswick Scientific Co., Inc., Edison, NJ, andUniversity of California, San Diego, La Jolla, 1995. BP

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