lecture 14 - industrial microbiology Flashcards
What is industrial microbiology?
“The application of scientific and engineering principles to the processing of materials by microbes to provide goods and services”.
Involves taking discoveries made in the laboratory and applying them on a large scale to provide useful things.
Why are microbes so good for Industrial use?
Diversity of microbial processes and the products possible. Grow on low grade, inexpensive and sometimes toxic materials
A small size and a high surface-to-volume ration which facilitate the rapid transport of nutrients into the cell
A very high metabolic rate (e.g. doubling times of 20 minutes are possible)
Adapted to a broad range of environments
What can microbial cells be used for in industry?
As a source of protein:
This used to be primarily for animal consumption
It is often termed single-cell protein although usually the whole cell is used.
Now used quite regularly in the production of products such as Quorn or Mycoprotein type products
Bacterial vaccines:
Living vaccines (attenuated)
Bacillus anthracis Anthrax Salmonella typhi Typhoid
Inactivated vaccines (using antigens from bacteria)
Nesseria meningitidis Meningitis Clostridium tetani Tetanus
What is the advantage of bioconversion?
Occur at relatively low temperatures
Occur in aqueous media rather than in organic solvents
Yield few, if any, side-products
Usually very specific (e.g. stereo-specific)
Growing cells, non-growing cells, spores and even dried cells can be used for biological conversions.
Describe the importance of enzymes
Biological catalysts
Important in the food and chemical industries because of their specificity, efficiency and potency under conditions of moderate temperature and pH.
Used extensively in washing powders (proteases and lipases)
What are the most important primary metabolites?
Amino acids
Purine nucleotides
Vitamins
Organic acids (e.g. citric acid).
Nutritional and genetic manipulations
can induce extremely high yields of metabolites.
What are the most important secondary metabolites?
An important group of products in medicine.
Include:
Antibiotics Toxins and Alkaloids - used in anti-tumour therapy Plant growth factors
Extremely diverse in structure and relate to survival tactics of microbes in natural environments.
Best known secondary metabolites are the antibiotics.
More than 5,000 have been discovered, with a rate of discovery of 300 per year.
Most are of no value.
About 75% of all antibiotics are produced by Actinomycetes, with 75% of these produced by the Streptomyces genus.
What is a fermenter?
The term “fermenter” is used to describe any large scale piece of equipment that is used to grow microorganisms in.
Most systems use liquid media (broth).
Can be sterile or non-sterile systems
Means something completely different in Biochemistry
Most fermentations necessitate the use of closed vessels which can operate with pure cultures.
Size of industrial scale production facilities are several orders of magnitude bigger than laboratory.
Several litres to several thousands of litres
How are fermenters constructed?
Constructed from stainless steel or mild steel lined with glass or plastic
Smooth to reduce cleaning problems.
No sharp corners
Capable of withstanding sterilisation
How is the temperature regulated in a fermenter?
During metabolism microbes generate heat
Vessels have to incorporate cooling equipment
Small vessels (up to 1000 l) can incorporate cooling jackets but larger vessels usually contain cooling coils
How does stirring take place in a fermenter?
Agitation and mixing in most fermenters is achieved with stirring gear.
Most common are vertical paddles which create a circular movement in the medium.
Need baffles to stop bulk movement
How does aeration take place in a fermenter?
Most processes are aerobic and require large volumes supplied through a sparger.
Oxygen is usually supplied as air
Sterilised by filtration through mineral wool filters impregnated with polystyrene.
What is the effect of stirring and aeration
Agitation and its associated turbulence improves aeration in several ways:
Dispersing the air in smaller bubbles Preventing coalescence of bubbles Forcing bubbles to take a tortuous path and thereby increasing their time in the culture
The supply of oxygen should not be the rate-limiting step
An optimal regime of stirring and aeration is required for every kind of fermentation.
Increases nutrient transfer
Increases the rate of transfer of metabolic products
Increases the rate of heat transfer
Purges the medium of volatile by-products of metabolism.
Prevents formation of clumps of cells.
What process control equipment is used in a fermenter?
Temperature - Resistance thermometers
pH - pH electrodes / controllers
Foam - Anti-foams to prevent foam formation.
How is a fermenter operated?
- Sterilisation of Vessels and Equipment:
Vessel is injected with steam (the medium is prepared slightly concentrated to account for dilution with steam).
Stirring occurs whilst the sterilisation process is undertaken.
At 100˚C the exhaust valve is closed and pressure and temperature increase to provide a temperature of 120˚C to 150˚C.
- Inoculation of Fermenter
Organism is usually grown up freshly for each fermentation and discarded afterwards.
Stock cultures grown in a small volume system (1 to 2 l) under optimal growth conditions
Repeated at 20-fold increases until the correct volume is achieved
Inoculum of between 1/10 and 1/5 of the volume of the final fermenter is used.
Idea is to dilute and swamp any contamination
- Process Control / fermenter operation
Fermentation systems must be efficiently controlled Control over: pH Temperature Aeration Mixing Foam control
All achieved using feedback control loops controlled by computer.
