Fermentation Technology
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| 01.07.2011 | Author: sathya | Posted in Fermentation Technology, Food Science & Technology | | Print
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Fermentation Technology
Introduction
Fermentation is the oldest of all biotechnological process.
To a microbiologist the word means any process for the production of a product by the mass culture of microorganisms.
Fermentation is a process of chemical change caused by microorganisms or their products.
To a biochemist, however, the word means an energy-generating process in which organic compounds act as both electron donors and acceptors, that is, an anaerobic process where energy is produced without the participation of oxygen or other inorganic electron acceptors.
New definition: a form of metabolism in which the end products could be further oxidized
For example: a yeast cell obtains 2 molecules of ATP per molecule of glucose when it ferments it to ethanol
Some important fermentation products.
MICROBIAL GROWTH
A. Requirement for artificial Culture
The rate of growth of microorganisms is dependent upon several culture conditions, which should provide for the energy required for various chemical productions.
- Define medium à nutritional, hormonal, and substratum requirement of cells
- In most cases, the medium is independent of the bioreactor design and process parameters
- The type: complex and synthetic medium (mineral medium)
Even small modifications in the medium could change cell line stability, product quality, yield, operational parameters, and downstream processing.
Medium composition
Fermentation medium consists of:
- Macronutrients (C, H, N, S, P, Mg sources à water, sugars, lipid, amino acids, salt minerals)
- Micronutrients (trace elements/ metals, vitamins)
- Additional factors: growth factors, attachment proteins, transport proteins)
For aerobic culture, oxygen is spared.
B. Phases of microbial growth
Initially, growth does not occur and this period is referred to as the lag phase and may be considered a period of adaptation. Following an interval during which the growth rate of the cells gradually increases, the cells grow at a constant, maximum rate and this period is referred to as the log or exponential phase.
The specific growth rate during the exponential phase is the maximum for the prevailing conditions and is described as the maximum specific growth rate.
After a certain time of exponential phase, the rate of growth slows down, due to continuously falling concentrations of nutrients or continuously increasing of toxic substances. This phase is referred to as the declaration phase.
APPLICATIONS OF FERMENTATION
Microbial fermentations may be classified into the following major group
(i) Those that produce microbial cells (biomass) as the product.
Microbial biomass is produced commercially as single cell protein (SCP) for human food or animal feed and as viable yeast cells to be used in the baking industry.
(ii) Those that produce microbial metabolites.
(iii) Those that produce microbial enzymes.
(iv) Those that modify a compound which is added to the fermentation the transformation processes.
(v) Those that produce recombinant products.
Design of Industrial Fermentation Process
The fermentation process requires following:
- A pure culture of the chosen organism, in sufficient quantity and in correct physiological state.
- Sterilized, carefully composed medium for growth of organism.
- A seed fermenter.
- A production fermenter.
Types of Culture Systems
1) Batch processing or culture.
2) Continuous processing or culture.
3) Fed-batch processing or culture.
4)
