Features of Biotechnological Importance in Microorganisms

Microbial Products

Most of the natural products constituted by carbon, nitrogen, hydrogen, oxygen and phosphorus can be fermented under anaerobic conditions by microorganisms. There are many fermentation products used commercially (Fig. 14.6). A list of some microorganisms and their products are given in Table 14.1.

Primary Metabolites

After inoculation when microbial growth is in exponential or trophophase many intermediate metabolic products are produced. These are further needed either in growth (e.g. amino acids, nucleotides, proteins, carbohydrates, lipids, vitamins, etc), or energy yielding catabolism (e.g. acetone, ethanal, butanol, organic acids, etc). Therefore, the metabolites produced during trophophase are known as 'primary metabolites'. The concentration of some of the metabolites exceeds many times more than required by the producers. The principal primary metabolites and the respective micro-organisms are given in Table 14.1.

Secondary Metabolites

When the trophophase of growing culture is over, then starts the idiophase. Microbial products other than primary metabolites produced during idiophase by slow growing or non-growing cells of microorganisms are known as secondary metabolites or idiolites such as toxins, gibberellins, alkaloids, and antibiotics. The secondary metabolites play no role in growth of microorganisms. It is produced by a limited number of microorganisms (Table 14.1) when depletion of one or more nutrients is caused in culture medium.
  Content
» Fermentation
» Microorganisms
» Cultures of microorganism

» Solid or semisolid culture

» Batch culture

» Continuous culture

» Fed-batch culture
» Metabolic pathways in microorganisms

» Glycolysis or EMP pathway

» The entner-doudoroff pathway

» The pentose phosphate pathway
» Microbial products

» Primary metabolites

» Secondary metabolites

» Enzymes

» Microbial biomass

Enzymes
Enzymes are naturally occurring biocatalysts which accelerate metabolic reactions. Various metabolic activities and production of primary and secondary metabolites are not possible without the involvement of enzymes. Enzymes produced during fermentation are mostly extracellular but a few are intracellular for example asparaginase, invertase and uric acid. Intracellular enzymes may be produced in industries, but with many difficulties. The important extracellular enzymes are amylases, cellulases, invertase, 6-galactosidase (lactase), esterase, lipases, proteases.

Table 14.1. Microorganisms and their products.


Algae
Microbial products
Primary metabolites
(1)
Secondary metabolites
(2)
Enzymes
(3)
Others
(4)

Chlorella sorokiniana
-
-
-
SCP

Spirulina maxima
-
-
-
SCP

S. platensls
-
-
-
SCP



Bacteria
Microbial products
Primary metabolites
(1)
Secondary metabolites
(2)
Enzymes
(3)
Others
(4)

Acetobacter aceti
Acetic acid
-
-
-

Acetobacterium woodii
Acetic acid
-
-
-

Bacillus brevis
-
Gramicidin  
-
-

B. polymyxa
-
Polymyxin B
Amylase
-

B. popilliae
-
Endotoxin
-
-

B. subtilis
-
Bacitracin
-
-

B. thuringiensis
-
Endotoxin
-
-

Clostridium aceticum
Acetic acid
-
-
-

Gluconobacter
suboxydans
Vinegar
-
-
-

Meihylophilus
methylotrophus
Glutanic acid
-
-
-

Pseudomonas
denitrificans
Vitamin B12
-
-
Yoghurt

Actinomycetes :
-
-
-
-

Micromonospora
purpurea
-
Gentamicin
-
-

Nocardia mediterranei
-
Rifamycin
-
-

Streptomyces
aureofaciens                 
-
Tetracycline
-
-

S. tradiae                     
-
Neomycin
-
-

S. griseus                     
-
Streptomycin
-
-

S. noursei                     
-
Nystatin
-
-

Fungi :
-
-
-
-

Aspergillus niger   
-
Citric acid
-
-

A. oryzae
-
-
Amylase Cellulase Amylase
SCP,
Soya sauce

Candida lipolytica         
-
-
Lipase
Soya sauce

C. utilis                         
-
-
-
SCP

Cephalosporium
acremonium                  
-
Cephalosporin
-
-

Fusarium
moniliforme                  
-
-
-
SCP

Gibberella
fujikuroi                
-
Gibberellin
-
-

Morchella esculenta     
-
-
-
SCP

Penicillium
chrysogenum                 
-
Penicillin
-
-

Rhizopus arrihizus,
-
-
-
-

R. nigricans                  
-
Steroides
-
-

Saccharomyces
cerevisiae                       
-
-
-
SCP, wine, bakery

S. lipolytica                
-
-
-
SCP

Trichoderma                   
harzianum,                     
T. reesei, T. viride          
-
-
Cellulase
-
SCP = Single Cell Protein.


Microbial Biomass

Microbial cells which produce many commercial products, themselves serve as main source of biomass. Microbial biomass is also known as microbial protein or single cell protein (SCP). SCP plays a significant role in supplying the protein in world food shortages. Production of SCP and its application have been described in detail in Single Cell Protein (SCP) and Mycoprotein.
  Reduction of glucose into some important products during fermentation. 1-yeast; 2-propionibacteria; 3-clostridia; 4-coli-aerogenes groups; 5-lactic acid bacteria (modified after Schlegel, 1986).
 

Fig. 14.6. Reduction of glucose into some important products during fermentation. 1-yeast; 2-propionibacteria; 3-clostridia; 4-coli-aerogenes groups; 5-lactic acid bacteria (modified after Schlegel, 1986).