Quiz 3 - Pt. 3 (Factors - Thermal Sterilization Flashcards
Factors for Consideration in Reactor Design
Heat removal
Foam Control
Providing Oxygen
Sterilization
Heat removal
____ produces heat, removed by internal coils or reactor jackets.
Cellular metabolism
Foam Control
- ____ produces compounds that promote foaming.
- Controlled by mechanical foam breakers and chemical additives.
- Cellular metabolism
Providing Oxygen
- _____ requires oxygen.
- ______ makes smaller bubbles and increases residence time.
- Cellular respiration
- Sparged air impeller
Single organism desired. Steam and filtering.
Sterilization
What Factors Limit the Size of Reactors?
Ability to provide oxygen and remove heat.
Types of reactors
- Stirred-tank
- Bubble column
- Airlift
- Propeller Loop
- Jet Loop
_____
* Empirical
* Make the controlling regime the same in the small scale as in the large scale
Scale-Up
Scale - Up Criterion
- Power Input - ____
- _____ - mixing time
- Tip speed - _____
- Reynolds number - _____
- OTR (oxygen transfer rate)
- Liquid circulation rate
- Shear
- Geometry
- Scale-up by requiring characteristic times to be constant between the small and large scale.
- Many types of characteristic times: related to ____ (5)
mixing
diffusion
oxygen mass transfer
reaction
growth
type of reactor?
- Good oxygen mass transfer
- High energy requirement for mixing
- Seal to maintain, keep sterile
Agitated Tank
type of reactor
- Low shear environment
- No seal needed
- Restricted to low viscosity
- Less mixing than agitated tank
- Bubble coalescence limits upper air flow rate
bubble column
type of reactor?
- Better mixing than bubble column with same low shear and energy requirements and lack of seal
- work with higher viscosity liquids than bubble columns
- Still less mixing than agitated tank
Loop reactors
Agitated Tanks pt. 1
- _____ breaks bubbles into smaller ones to provide for better oxygen mass transfer
- _____ are typically glass,
- ____ are typically stainless steel
- Heat removal/addition is typically by ____ along the wall, or a ____ around the tank
- impeller
- bench-top tanks,
- commercial fermenters
- coils, water jacket
Agitated Tanks Pt. 2
- _____ prevents foaming problems, but can cause additional _____ transfer resistance
- “_____”- volume of liquid in tank; does not include head space
- _____ for agitator shaft must not allow contamination
- _____ are used to augment mixing and gas dispersion
- Antifoam, mass
- working volume
- seal
- baffles
type of impeller
- ____ : has disc with ____ blades.
- Pumps fluid in a ____ direction.
- Compartmentalization with ____ impellers on a shaft.
- rushton impeller
- 6 to 8
- radial
- multiple
type of impeller?
- ____: pumps liquid in a ____ direction.
- Lower energy for the same oxygen mass transfer.
- Lower shear rates.
- Axial flow impeller
- vertical
Oxygen Mass transfer mechanism
- ____ phase oxygen concentration
- Transfer across stagnant ____ layer
- Partitioning into the ____ phase (C” at saturation)
- Transfer across stagnant ____ layer
- ____ concentration (C₁)
- Transfer across stagnant liquid layer to ____
- Bulk gas
- gas
- liquid
- liquid
- bulk liquid
- cell
Common On-line Instrumentation
- pH
- Temperature
- Dissolved oxygen
- Foam
- Flow rates
- Level Off-gas composition (CO2, O2, VOCs)
Control
- ____________ is generally not as sophisticated as chemical production process control due to a lack of on-line sensors.
Fermentation process control
Why is there a lack of on-line sensors?
- Each probe into the fermentor increases the _____,
- difficult to sterilize some probes,
- probe fouling,
- probe placement (gradients within the fermentor).
- probability of contamination
Oxygen Mass Transfer
- Transfer rate at steady state is determined by the _____ (just like on a highway).
slowest rate
- As we have seen before, for an oxygen-transfer rate limited process or at steady state
- _____ is not the rate at which you provide air to the reactor.
- You will actually provide much more oxygen to the ____ than is transferred to the ____.
- oxygen mass transfer
- reactor, cell
the value of the product K_La(volumetric transfer coefficient) often determined the ____
maximum cell mass X
absence of detectable viable organisms
sterilization
reduction in the amount to detectable, viable organisms.
Disinfection
- Sterilization is ______: some portion of the the population is more resistant to sterilizing agents than other portions.
probabilistic
Determining O_{2} Mass Transfer
- Correlations can be used to predict the _____ k_{L}*a
- volumetric transfer coefficient
Methods of Sterilization
- filter
- heat
- radiation
- chemical
Heat sensitive liquids and gases. Most common for gases - P important.
filter
Most common for liquids and equipment. Steam. Typically 121°C. Time and T important. Risk degrading medium components.
heat
method of sterilization
* _______ : Surfaces.
* ______: Risk toxic residues.
- radiation
- chemical
a faster growing contaminating organism can outgrow the desired organism and cause washout of the desired organism.
chemostat
the product can be biologically contaminated (could be lethal) or the purity profile could be significantly effected (indust. fermentations 100 kl).
batch
Experimental Determination of O₂ Mass Transfer
- The previous correlation offer design estimates.
- Medium components, _____, and ____ can affect k_La and oxygen solubility
- ____ experiments can be done to measure k_La
- Unsteady state, steady state, dynamic and sulfite methods to measure k_La
- temperature, pressure
- simple
_________
Fill the reactor with medium only no cells. Measure the ____ concentration in the medium. Remove oxygen from the medium by sparging with ____. Introduce ____, and record the increase in DO.
Unsteady Method
DO
N₂
air
to clean with the purpose of removing possible biological and nonbiological threats to human health.
sanitize
to greatly reduce the number of living organisms.
disinfect
to eliminate all viable organisms present (often our goal).
sterilize
can be sterilized by heat, microfiltration, radiation, chemical agents, UV light
fluids and process equipment
a cell, spore, or virus that is dead will not reproduce (cells and viruses) or germinate (spores) under conditions favorable for growth (opposite is “viable”).
death
Requires an oxygen gas analyzer for the effluent air. Perform an O, mass balance to obtain OUR (Oxygen Uptake Rate).
Steady-State Method
Dynamic Method
* Utilizes a fermentor with ____.
* Requires only a DO meter
* The air to the fermentor is shut off, and the DO decreases due to ____ by the microorganisms. The air is then turned on, and the the DO increases.
- actively growing cell
- consumption
- When the air is off, k, a = 0, so the slope of DO vs. time is equal to -qo2X.
- The slope of the _____ with time can be determined from ____ to the curve. The slope of the plot dC₁/dt-q02X vs (C-CL) will be k₁a.
- ascending curve
- tangents
Specific Agents pt. 1
- ___________ a common method.
- _______ is common for the insides of reactors that can’t be heat or steam sterilized.
- Media that can’t be heat sterilized (___, _____, __) must be filter sterilized using filters with narrow pore-size distributions.
- thermal sterilization
- ethylene oxide
- heat labile vitamins, proteins, sugars
Specific Agents pt. 2
- ____ in water with HCl to pH 2 is a good sterilizing fluid.
- Weak (3%) ____ is commonly used to sterilize filtration equipment.
- 70% v/v ETOH
- sodium hypochlorite solution
is often assumed to be a function of temperature (as before):
- k_{d} - specific death constant
