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PinkMonkey Online Study Guide-Biology

10.1 Fermentation

Fermentation is a process very much similar to anaerobic respiration. It is a metabolic process in many micro-organisms and involves oxido-reduction reactions resulting in the breakdown of complex organic molecules into various end products with the release of energy. Fermentation is mostly extracellular and is brought about with the help of enzymes released by the micro-organisms. The end products or the various intermediate products (primary and secondary metabolites) of the fermentation activities of many micro-organisms are highly useful. Hence, micro-organisms have been commercially exploited by the fermentation industry. Thus, with reference to industrial microbiology, fermentation may be defined as "a process for the production of useful products through mass culture of micro-organisms."

Micro-organisms involved in the fermentation industry : More than a million different micro-organisms are known to exist in nature. However, only a few hundred species are of commercial importance. Some of these species are listed below.


Chlorella sp., Spirulina sp:,etc.


Acetobacter lacti, Bacillus subtilis, Pseudomonas denitrificans, etc.


Streptomyces aureofaciens, S.griseus, Nocardia sp ;,etc.


Aspergillus niger, Penicillium notatum,

P. chrysogenum, Sacchromyces sp;,Gibberella fujikuroi, Fusarium moniliforme, etc.

Fermenter : A fermenter is a vessel designed to carry out fermentation process, (i.e. the microbiological reactions under the controlled conditions). Hence, a fermenter is also called a bio-reactor. The fermenter allows long term operation in aseptic conditions. It has the necessary arrangements for adequate aeration, agitation, pH control, temperature control, sampling, harvesting, etc. Thus, it is very convenient for operation in the fermentation industry.

Uses of fermentation

  1. Useful intermediate products : The various intermediate compounds produced during fermentation activity are classified as primary and secondary metabolites. Some of the commercially important metabolites are (a) Primary metabolites, such as amino acids, proteins, carbohydrates, vitamins, acetone, ethanol, organic acids etc. and (b) Secondary metabolites such as antibiotics, toxins, alkaloids, gibberellins, etc.

  2. Enzymes : Enzymes produced by the micro-organisms during fermentation include amylases, cellulases, invertase, esterase, lipase, protase, lactase, etc.

  3. Microbial biomass: After the process of industrial fermentation is over, the exhausted cells of the micro-organisms (in the fermenter) serve as microbial biomass. It is also known as microbial protein or single cell protein (SCP). It is an important source of proteins.

Table of Contents

10.0 - Introduction
10.1 Fermentation
10.2 Manufacture of Alcohol
10.3 Antibiotics
10.4 Vitamins

Chapter 11


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