Quiz 3 - Pt. 3 (Factors - Thermal Sterilization Flashcards
1
Q
Factors for Consideration in Reactor Design
A
Heat removal
Foam Control
Providing Oxygen
Sterilization
2
Q
Heat removal
____ produces heat, removed by internal coils or reactor jackets.
A
Cellular metabolism
3
Q
Foam Control
- ____ produces compounds that promote foaming.
- Controlled by mechanical foam breakers and chemical additives.
A
- Cellular metabolism
4
Q
Providing Oxygen
- _____ requires oxygen.
- ______ makes smaller bubbles and increases residence time.
A
- Cellular respiration
- Sparged air impeller
5
Q
Single organism desired. Steam and filtering.
A
Sterilization
6
Q
What Factors Limit the Size of Reactors?
A
Ability to provide oxygen and remove heat.
7
Q
Types of reactors
A
- Stirred-tank
- Bubble column
- Airlift
- Propeller Loop
- Jet Loop
8
Q
_____
* Empirical
* Make the controlling regime the same in the small scale as in the large scale
A
Scale-Up
9
Q
Scale - Up Criterion
- Power Input - ____
- _____ - mixing time
- Tip speed - _____
- Reynolds number - _____
A
- OTR (oxygen transfer rate)
- Liquid circulation rate
- Shear
- Geometry
10
Q
- Scale-up by requiring characteristic times to be constant between the small and large scale.
- Many types of characteristic times: related to ____ (5)
A
mixing
diffusion
oxygen mass transfer
reaction
growth
11
Q
type of reactor?
- Good oxygen mass transfer
- High energy requirement for mixing
- Seal to maintain, keep sterile
A
Agitated Tank
12
Q
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
A
bubble column
13
Q
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
A
Loop reactors
14
Q
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
A
- impeller
- bench-top tanks,
- commercial fermenters
- coils, water jacket
15
Q
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
A
- Antifoam, mass
- working volume
- seal
- baffles
16
Q
type of impeller
- ____ : has disc with ____ blades.
- Pumps fluid in a ____ direction.
- Compartmentalization with ____ impellers on a shaft.
A
- rushton impeller
- 6 to 8
- radial
- multiple
17
Q
type of impeller?
- ____: pumps liquid in a ____ direction.
- Lower energy for the same oxygen mass transfer.
- Lower shear rates.
A
- Axial flow impeller
- vertical
18
Q
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 ____
A
- Bulk gas
- gas
- liquid
- liquid
- bulk liquid
- cell
19
Q
Common On-line Instrumentation
A
- pH
- Temperature
- Dissolved oxygen
- Foam
- Flow rates
- Level Off-gas composition (CO2, O2, VOCs)
20
Q
Control
- ____________ is generally not as sophisticated as chemical production process control due to a lack of on-line sensors.
A
Fermentation process control
21
Q
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).
A
- probability of contamination
22
Q
Oxygen Mass Transfer
- Transfer rate at steady state is determined by the _____ (just like on a highway).
A
slowest rate
23
Q
- 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 ____.
A
- oxygen mass transfer
- reactor, cell
24
Q
the value of the product K_La(volumetric transfer coefficient) often determined the ____
A
maximum cell mass X
25
**absence** of detectable viable organisms
sterilization
26
**reduction** in the amount to detectable, viable organisms.
Disinfection
27
* **Sterilization** is ______: *some portion* of the the population *is more resistant* to sterilizing agents than other portions.
probabilistic
28
Determining O_{2} Mass Transfer
* **Correlations** can be used to predict the _____ k_{L}*a
* volumetric transfer coefficient
29
**Methods of Sterilization**
* filter
* heat
* radiation
* chemical
30
Heat sensitive liquids and gases. **Most common for gases** - P important.
filter
31
**Most common for liquids** and equipment. Steam. Typically 121°C. Time and T important. Risk degrading medium components.
heat
32
method of sterilization
* _______ : Surfaces.
* ______: Risk toxic residues.
* radiation
* chemical
33
a faster growing contaminating organism can **outgrow the desired organism** and cause **washout of the desired organism**.
chemostat
34
the **product can be biologically contaminated** (could be lethal) or the purity profile could be significantly effected (indust. fermentations 100 kl).
batch
35
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
36
_________
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
37
to **clean** with the purpose of removing possible biological and nonbiological threats to human health.
sanitize
38
to **greatly reduce** the number of living organisms.
disinfect
39
to **eliminate** all viable organisms present (often our goal).
sterilize
40
can be **sterilized by heat**, microfiltration, radiation, chemical agents, UV light
fluids and process equipment
41
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
42
**Requires an oxygen gas analyzer** for the effluent air. Perform an O, mass balance to obtain OUR (Oxygen Uptake Rate).
Steady-State Method
43
**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
44
* 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
45
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
46
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
47
is often assumed to be a **function of temperature** (as before):
* k_{d} - specific death constant
