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Here we detail about the six important parameters of fermentation biotechnology.
The six parameters are: 1. Preliminary Investigations 2. Scale Up 3. Culture Preservation 4. Feedstocks for Fermentation Processes 5. Fermenter Design and Operation 6. Downstream Processing.
1. Preliminary Investigations:
The starting point for a fermentation process is the discovery that a microorganism makes a useful product.
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Such a discovery does not by itself constitute a sufficient basis for a successful industrial fermentation — the organism may grow poorly, the medium used may be expensive, and yields of the desired product may be very low.
These problems are overcome by improving the performance of the microorganism genetically and by providing it with the optimum environment for growth and product formation.
2. Scale Up:
When efficient growth and product formation by the organism and product recovery from the fermenter have been standardised on the pilot plant scale, and if it is found to be satisfactory, commercial production becomes feasible.
3. Culture Preservation:
A fungal strain that gives high yields of a valuable product is a precious asset. Such a strain devotes a substantial proportion of its carbon source to the formation of a metabolite in quantities which are unnecessary for survival. Repeated subculture is hence likely to result in the replacement of the high-yielding strain with variants that produce less of the desired metabolite and devote more of their resources to achieving higher growth rates.
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Excessive subculture must, therefore, be avoided, and the material needed for initiating fermentations kept in a non-growing state. The ideal starting point for preparing cultures for preservation will be a master culture that has originated from a single uninucleate haploid cell and is hence genetically uniform, and which has been shown, by testing subcultures, to have the desired properties. From such a master culture a set of subcultures is prepared and from them material for preservation.
4. Feedstocks for Fermentation Processes:
For a successful fermentation, the fungus must behave in a consistent, predictable manner, giving similar growth rates and metabolite yields in successive fermentations. A crucial factor in achieving this is to provide a nutrient medium that contains utilizable sources of carbon, nitrogen and other essential elements in the appropriate amounts and ratios. This is easily done in the laboratory by making use of pure chemicals, but on an industrial scale this would be far too expensive. The selection of the right raw materials (feedstocks) for medium preparation is a key factor in the success of an industrial fermentation.
5. Fermenter Design and Operation:
Most industrial fermentations are carried out in stirred tank fermenters. A stirred tank fermenter (Fig. 11-1) is a cylindrical vessel designed to contain a volume of sterile medium that can be inoculated, aerated, stirred, monitored by sensing devices, heated or cooled, and sampled or fed with additional materials, all without bringing about contamination. It is constructed of high-grade stainless steel, to avoid corrosion by media or leaching of toxic metals into the medium.
6. Downstream Processing:
When a fermentation is complete it will contain cells (biomass) in a large volume of spent medium. In brewing, the spent medium is itself the desired product, and in single cell protein production—the biomass. Usually, however, the desired product is a minor component of the cells or broth.
A liter of broth with biomass may, for example, contain only 1 g of a required enzyme or 10 g of an antibiotic. A small amount of product, hence, has to be separated from a large volume of waste material. A fermentation will be economic only if the downstream processing that accomplishes this is efficient.
A series of steps (unit operations) will be required in the concentration and purification of a product. Each unit operation involves expense in terms of equipment, manpower and energy or chemicals, and at each step there will be some loss of product. The number of steps hence, has to be kept to a minimum.
