Preservation is mixed with suspension of fungal or

Preservation of industrial microorganisms

1-     
 As slopes (kept in the refrigerator)

2-     
 Lyophilization (bacteria or
fungal spores) are suspended in a suitable medium, quick freezing then drying
under vacuum with survival rate of about 50% , stored for many years without
loss of viability

3-     
Soil culture (sterile moist soil is mixed with suspension of fungal or
bacterial spores, dried in desiccators, stored for many years)

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4-     
 Paraffin seal method (actively
growing cultures are covered with 1 cm layer of sterile paraffin oil, for
cultures that do not stand drying)

5-      Quick freezing method (cultures are quickly
frozen and held at -20°C or less up to -80°C in the presence of glycerol to
reduce damage due to freezing)

 

 

 

 

Fermentation medium

The nutritional needs of microorganisms are diverse. The Fermentation
medium consists of:

1-     
 Macronutrients (C, H, N, S, P, Mg sources in water,
sugars, lipids, amino acids, salts, minerals)

2-       Micronutrients (trace
elements/ metals, vitamins)

3-     
 Additional factors: growth factors, attachment
proteins, transport proteins, etc).

4-     
For aerobic
culture, oxygen is also included

5-     
Precursors:
Directly incorporated into the desired product: Phenyl acetic acid into
Penicillin G

6-     
Inhibitors: To get
the specific products: e.g. Sodium barbital for Rifamycin

7-     
Inducers: Majority
of the enzymes are inducible and are synthesized in response to inducers: e.g.
Starch for Amylases, Pectin for Pectinase

8-     
Chelators: are the
chemicals used to avoid the precipitation of metal ions. Chelators like EDTA,
Citric acid, are used in low concentrations.

9-     
Trace elements :
Fe, Zn, Cu, Mn, Mo, Co

10-  Antifoaming agents: Esters, Fatty acids, Silicones,
Sulphonates, Polypropylene

11-  Buffers: Calcium carbonate, Phosphates

12-  Growth factors: Some microorganisms cannot synthesize the
required cell components themselves and need to be supplemented: E.g. Thiamine,
Biotin, Calcium pentothenate

 

 

 

 

 

 

 

 

 

 

Submersion technique

In the submersion processes, the microorganisms grow in a
liquid medium. The medium is held in fermenters and stirred to obtain a
homogeneous distribution of cells and medium.

All-important industrial processes (production of biomass and
protein, antibiotics, and enzymes) are carried out by submersion processes.

The submersion processes may be run in: Batch – fed batch –
continuous

 

 

1-     
Batch fermentation
:

 

Most fermentations are batch processes

Batch processing or batch culture: Nutrients and
the inoculum are added to the sterile fermentor, fermentation process is
allowed to proceed for limited time under controlled conditions from aeration
and agitation, etc

After certain incubation period (the desired
amount of product is present) the process stopped, yield recovered, the tank is
cleaned and a new batch is set up.

The best advantage of batch processing is the optimum
levels of product recovery. However the disadvantages are the wasting of unused
nutrients, and the time lost between batches.

 

2-     
Fed batch
fermentation process:

 

In the fed-batch system, a fresh aliquot of the
medium is continuously or periodically added, without the removal of the
culture fluid that has the advantage of avoiding the toxic effects of a medium
component.

?The production of penicillin, as a secondary
metabolite, is best done by fed-batch method. The culture is maintained at low
levels of biomass and phenyl acetic acid (PAA), the precursor of penicillin, is
fed into the fermentor continuously, but at a low rate, as the precursor is
toxic to the organism at higher concentrations

 

3-     
 Continuous processing or culture (Chemostat )

 

 Fermentation
process allowed to proceed continuously with continuous supply of required
nutrients and products are withdrawn regularly. Nutrients are added to the
fermentation vessel and products are withdrawn at the same rate

 

 

 

 

 

 

 

 

 

 

Primary and Secondary Metabolites:

 

Primary
metabolites are produced during active cell growth   They include Intermediates in metabolic pathways
(TCA cycle, pathways leading to protein and nucleic acid production)

 

 

Secondary metabolites are produced near the onset of stationary phase They
are not part of the “central” metabolic pathways . Therefore they are not
essential for growth.

Examples include: Actinomycetes (eg Streptomyces)
,Fungi (eg Penicillium) ,Sporeforming bacteria (Bacillus)  Secondary metabolites are produced as growth
slows/stops in batch cultures .Antibiotics are of major industrial importance

Antibiotics are compounds produced naturally from some
microorganisms that kill or inhibit the growth of other microbes. They are typically
secondary metabolites . Most antibiotics in clinical use are produced by
filamentous fungi or actinomycetes  Microbes
are obtained from nature in pure culture

 

Antibiotics are produced industrially by the process of
fermentation, where the source microorganism is grown in large containers
(100,000 – 150,000 liters or more) containing a liquid growth
medium.