Ik a fermentation process is to yield a product at a competitive price, the chosen micro-organism or animal cell culture should give the desired end-product in predictable, and economically adequate, quantities. A number of basic objectives are commonly used in developing a successful process which will be economically viable.

1. The capital investment in the fermenter and ancillary equipment should be confined to a minimum, provided that the equipment is reliable and may be used in a range of fermentation processes.

2. Raw materials should be as cheap as possible and utilized efficiently. A search for possible alternative materials might be made, even when a process is operational.

3. The highest-yielding strain of micro-organism or animal cell culture should be used.

4. There should be a saving in labour whenever possible and automation should be used where it is feasible.

5. When a batch process is operated, the growth cycle should be as short as possible to obtain the highest yield of product and allow for maximum utilization of equipment. To achieve this objective it may be possible to use fed-batch culture (Chapters 2 and 4).

6. Recovery and purification procedures should be as simple and rapid as possible.

7. The effluent discharge should be kept to a minimum.

8. Heat and power should be used efficiently.

9. Space requirements should be kept to a minimum, but there should be some allowance for potential expansion in production capacity.

10. All the above must comply with safety guidelines and regulations.

The consideration of so many criteria means that there may have to be a compromise for the particular set of circumstances relating to an individual process. Winkler (1991) identified three key economic objectives in the fermentation stage: maximum product yield, process productivity and substrate utilization. However, these criteria may be overridden by the demands of subsequent purification stages for high product concentration and high product purity which may in turn be overridden by safety considerations.

In any process it is important to know the cost breakdown (Table 12.1), so that it may be seen where the biggest potential savings may be achieved. In a review of a number of processes, Nyiri and Charles (1977) concluded that four basic components contributed to the process cost in the following decreasing order: raw materials, fixed costs, utilities, labour. When raw materials are a major part of the total cost it is obvious that media and microbial strain-improvement research should form a major part of a development programme. Development work on components contributing little to the cost of the product could not be justified.

Costs quoted in this chapter have been taken from the source of information and are applicable only at the time of that publication. Atkinson and Mavituna (1991) have discussed the use of cost indices to update historical data. _

Caution is necessary when examining some examples of potential fermentation processes, since the capital and operating costs normally have been estimated us

Table 12.1. Production costs breakdown expressed as percentages of total cost

Hem Product

Hem Product

Table 12.1. Production costs breakdown expressed as percentages of total cost

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