Enzyme Inducers and Fermentation Control

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Questions and Answers

What is the primary function of dihydroxy acetone in the context mentioned?

It replaces acetaldehyde. (correct)

It increases cell wall rigidity.

It serves as an antifoam agent.

It enhances protein metabolism.

Which of the following is an example of an inducer for amylase production?

Maltose (correct)

Acetaldehyde

Fatty acids

Silicones

What characteristic should an ideal antifoam agent possess?

It should require high doses.

It should be metabolized quickly.

It should not be toxic. (correct)

It should be heavily concentrated.

What is a major component contributing to total product cost in fermentation processes?

Raw materials costs Signup and view all the answers

What type of media contains known inorganic or organic compounds?

Synthetic or defined culture media Signup and view all the answers

For which enzyme is pectin used as an inducer?

Pectinase Signup and view all the answers

In what way can foaming in fermentations be controlled?

Using mechanical foam breakers Signup and view all the answers

What is one of the properties of an effective antifoam agent?

It should destabilize protein films. Signup and view all the answers

What is a key advantage of defined media?

It has a consistent composition. Signup and view all the answers

Which of the following is NOT a type of media mentioned?

Specialized media Signup and view all the answers

What is a major limitation of crude media?

It may contain unwanted lethal components. Signup and view all the answers

What type of media is typically used for low volume, high value-added products?

Defined media Signup and view all the answers

Which of the following correctly describes crude media?

Composed of complex mixtures and agricultural products. Signup and view all the answers

Which of the following is an advantage of defined media?

Greater ease of upstream processing. Signup and view all the answers

What does the term 'selective differential media' imply?

It selectively encourages the growth of specific microorganisms while differentiating between types. Signup and view all the answers

What is a common issue associated with crude media during bioprocessing?

Bioprocess foaming. Signup and view all the answers

What percentage of steam is needed for continuous sterilization compared to batch processes?

20 to 25% Signup and view all the answers

What method is used to cool the medium after sterilization in continuous processes?

Flash cooling Signup and view all the answers

What is one disadvantage associated with steam injection in continuous sterilizers?

Dilution of the medium by condensate Signup and view all the answers

How is the raw medium initially preheated in a continuous sterilization system?

By hot, sterile medium in a heat exchanger Signup and view all the answers

What is a key variable that affects the performance of continuous sterilisers?

Nature of the fluid flow in the system Signup and view all the answers

What is a potential issue caused by foaming during steam injection?

Operational challenges in the flash cooler Signup and view all the answers

What is the role of the holding section in continuous sterilizers?

To maintain the sterilization temperature Signup and view all the answers

Why are heat exchange systems considered more expensive to construct than injection devices?

Complexity in design and materials required Signup and view all the answers

What is the primary purpose of filter sterilisation of liquids?

To screen out bacteria and particles larger than the pore size Signup and view all the answers

Which component is essential for effective filter sterilisation of media containing proteins?

Steam or radiation sterilised membranes Signup and view all the answers

What is a disadvantage of filter sterilisation compared to heat sterilisation?

Viruses and mycoplasma can pass through the membranes Signup and view all the answers

For what purpose is sterile air supplied to a bioreactor in fermentation systems?

To ensure an aseptic operating environment and oxygen supply Signup and view all the answers

What is the significance of having pore sizes between 0.2 and 0.45 μm in filter sterilisation?

It allows nutrients to flow through while blocking contaminants Signup and view all the answers

Why must membranes used for filter sterilisation be preflushed or prefiltered?

To avoid blockage from large particles Signup and view all the answers

What is the estimated range of microbial cells in ambient air?

10^3 to 10^4 cells per m3 Signup and view all the answers

What must be done to filter membranes before use in sterilisation processes?

They must be steam or radiation sterilised Signup and view all the answers

What is the primary advantage of using membrane cartridge filters over depth filters in industrial applications?

Higher filtration area in smaller volume Signup and view all the answers

What range of particle dimensions can depth filters typically remove?

2 to 10 μm Signup and view all the answers

Which of the following statements about depth filters is true?

They utilize mechanisms like impaction and interception to collect particles. Signup and view all the answers

What is the purpose of a pre-filter in the filtration process?

To remove large size particles and other contaminants Signup and view all the answers

Why are HEPA filters crucial in aseptic environments?

They filter out 99.97% of particles that are 0.3 μm and larger. Signup and view all the answers

What characteristic of membrane filters minimizes problems with filter wetting?

Hydrophobic nature Signup and view all the answers

Which statement about the operation of depth filters is incorrect?

Fluctuating air flow significantly enhances their effectiveness. Signup and view all the answers

What is a characteristic feature of the pores in membrane filter cartridges?

Uniformly sized, typically 0.45 μm or less Signup and view all the answers

Study Notes

Acetaldehyde and Dihydroxy Acetone

Acetaldehyde is no longer used in the production of dihydroxy acetone.

Inhibitors and Cell Wall Structure

Inhibitors can be used to change the cell wall structure.
This increases permeability, allowing metabolites to be released.
Penicillin and surfactants are used in glutamic acid production.

Inducers

Most enzymes are inducible.
Inducers are often substrates or substrate analogues.
Intermediates and products may be used as inducers.
Starch or dextrins induce amylase.
Maltose induces pullulanase.
Pectin induces pectinase.
Maltodextrins induce amylase.
Fatty acids induce lipase.
The cost of inducers is important.

Antifoams

Foaming is a common problem in fermentation.
It can be caused by components in the medium or by microorganisms.
Antifoams can be used to control foaming.
Antifoams reduce surface tension in the foam, destabilizing protein films.
Ideal antifoams disperse easily, act quickly and at low concentrations, have long-lasting effects, are not metabolized, not toxic, cheap, and do not interfere with fermentation.
Examples include fatty acids, silicones, and PPG 2000.

Cost of Media

Media can be a significant proportion of total product cost.
Raw materials costs can range from 38-77%.

Types of Media

Liquid media
Solid and semi-solid media
Natural cultural media or empirical culture media:
- Milk, diluted blood, vegetable juice, meat extracts
Synthetic or define culture media:
- Dilute, reproducible solutions of chemically pure, known inorganic or organic compounds
Liquid culture media:
- Living cells in tissue, callus, or organs. Also used with viruses, rickets, etc.
- Chick embryos are used for cultivating viruses.
Other types of media:
- Simple or basal media
- Complex media
- Selective media
- Differential media
- Selective differential media
- Enrichment media

Crude and Defined Media

Crude media:
- Made from complex mixtures (e.g., agricultural products)
- Individual ingredients can supply more than one requirement
- Can contain polymers or solids
Defined media:
- Made from pure compounds
Advantages of defined media:
- Consistent composition and quality
- Facilitate research and development
- Less likely to cause foaming
- Easier upstream processing (formulation, sterilization, etc.)
- Easier downstream processing (purification, etc.)
Disadvantages of defined media:
- Expensive
- Need to define and supply all growth factors, only mineral salts are present
- Yields and volumetric productivity can be poor. Cells have to work harder, proteins are not present, and some growth factors like amino acids may be missing.
Main use of defined media:
- Low volume/high value-added products, especially proteins produced by recombinant organisms
Some defined media may contain small amounts of undefined ingredients like yeast extract to supply growth factors.
Disadvantages of crude media:
- Variability in composition, quality, and supply
- Cost can fluctuate due to agricultural politics
- Unwanted components like iron or copper can be lethal
- Can cause bioprocess foaming
- Problems with upstream processing (medium pretreatment and sterilization)
- Problems with downstream processing (product recovery and purification)

Culture Media

Culture media (growth medium or culture medium) is a liquid or gel that supports the growth of microorganisms or cells.
The amount of steam needed for continuous sterilization is 20-25% of that used in batch processes.

Continuous Sterilizing Equipment

Continuous steam injection with flash cooling:
- Raw medium is preheated by hot, sterile medium in a heat exchanger.
- Steam is injected directly into the medium.
- The temperature of the medium rises quickly to the desired sterilization temperature.
- The medium is cooled instantly by flash cooling.
Heat transfer using heat exchangers:
- Raw medium is preheated using hot, sterile medium in a heat exchanger.
- The medium is then brought to sterilization temperature by further heat exchange with steam.
- The sterilization temperature is maintained in the holding section.
- The sterile medium is cooled by heat exchange with incoming medium before use in the fermenter.

Filter Sterilization of Liquids

Some fermentation media or medium ingredients are sterilized by filtration instead of heat.
Media containing heat-labile components like serum, differentiation factors, enzymes, and proteins are easily destroyed by heat.
Membranes used in filter sterilization are made of cellulose esters or polymers.
Filter sterilisation removes particles larger than the pore size.
Large membrane surface areas are needed for high filtration flow rates.
Membranes must be sterilized before use.
Disposable filters and cartridges are often used.
0.2 to 0.45 μm filter pores may allow viruses and mycoplasma to pass through.
0.1 μm sterilising-grade membrane filters can remove mycoplasma.
Filter sterilisation is used in mammalian cell culture processes.

Sterilization of Air

Sterile air is required for aerobic fermentation systems:
- To provide oxygen in bioreactor vessels for metabolic activity and microbial growth
- To maintain aseptic conditions in the bioreactor system
Ambient air contains dust, inert particles, bacteria, spores, and other contaminants.
Filtration is the most common method for sterilizing air in large-scale bioprocesses.
Depth filters:
- Compacted beds or pads of fibrous material like glass wool are used.
- The fibers have a larger distance between them than the bacteria and spores.
- Air particles penetrate the bed before being trapped.
- Depth of the filter depends on flow rate and contamination levels.
- Particles are trapped by impaction, interception, electrostatic effects, and diffusion.
- Not very effective for large fluctuations in air flow or wet air.
Membrane cartridge filters:
- Steam-sterilizable or disposable polymeric membranes are used.
- They act as surface filters, trapping contaminants like a sieve.
High-efficiency particulate air (HEPA) filters:
- Used to filter air moving into aseptic environments and out of contaminated ones.
Membrane filter cartridges:
- Pleated, hydrophobic filters with small, uniform pores.
- The hydrophobic nature minimizes wetting problems.
- High filtration area packed into a small cartridge volume.
Materials for membrane air filters:
- Ceramic materials: Durable, can be backwashed, steam sterilizable, economical.
- Polymeric materials: Polyvinyl alcohol (PVA), cellulose acetate, polysulfone, and other composites.
Pre-filters:
- Used before the main filtration membrane to remove large particles.

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Description

Explore the roles of inducers, antifoams, and inhibitors in fermentation. This quiz covers key concepts such as enzyme induction, cell wall structure alterations, and the prevention of foaming during fermentation processes. Test your knowledge on these important biochemical topics.