lecture 14 - industrial microbiology Flashcards

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1
Q

What is industrial microbiology?

A

“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.

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2
Q

Why are microbes so good for Industrial use?

A

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

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3
Q

What can microbial cells be used for in industry?

A

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
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4
Q

What is the advantage of bioconversion?

A

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.

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5
Q

Describe the importance of enzymes

A

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)

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6
Q

What are the most important primary metabolites?

A

Amino acids
Purine nucleotides
Vitamins
Organic acids (e.g. citric acid).

Nutritional and genetic manipulations
can induce extremely high yields of metabolites.

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7
Q

What are the most important secondary metabolites?

A

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.

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8
Q

What is a fermenter?

A

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

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9
Q

How are fermenters constructed?

A

Constructed from stainless steel or mild steel lined with glass or plastic

Smooth to reduce cleaning problems.

No sharp corners

Capable of withstanding sterilisation

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10
Q

How is the temperature regulated in a fermenter?

A

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

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11
Q

How does stirring take place in a fermenter?

A

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

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12
Q

How does aeration take place in a fermenter?

A

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.

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13
Q

What is the effect of stirring and aeration

A

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.

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14
Q

What process control equipment is used in a fermenter?

A

Temperature - Resistance thermometers

pH - pH electrodes / controllers

Foam - Anti-foams to prevent foam formation.

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15
Q

How is a fermenter operated?

A
  1. 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.

  1. 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

  1. 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.

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16
Q

Describe batch fermentation

A

Majority of industrial fermentations are batch processes

Good for secondary metabolites

Traditional way of doing things!

But doesn’t provide ideal conditions for growth at all times during process..

17
Q

Describe continuous fermentation

A

Turbidostat control
Rate at which the cells leave the reactor vessel governs the rate at which fresh nutrients enter.

Chemostat control
Rate at which a critical nutrient enters the reactor vessel is adjusted so that it limits the rate of the reaction.

18
Q

What factors affect downstream processing?

A

The choice of recovery process is based on

Location of the product (intra or extracellular)
Concentration of the product
Physical and chemical properties of the product
Intended use of the product
Minimum acceptable standard on purity required
Impurities in the broth that need to be removed
Cost

19
Q

What steps are undertaken in downstream processing?

A

Removal of solids
Primary isolation of product
Purification and concentration
Final product isolation

20
Q

What methods are used in downstream processing?

A
Distillation, 
 Precipitation & Flocculation
 Centrifugation
 Filtration, 
 Solvent Extraction
 Chromatography
21
Q

Give examples of “dirty” industrial microbiology

A

Sewage treatment (including methane production)
Biomining
Bioremediation