What is Scale-Up of Microbial Process?

The issue in producing large amount of product (e.g. curd and acetone) has also been discussed.

Microorganisms are influenced by the continuously changing environment when moving inside the large fermentor. To avoid these problems the large scale should be taken as the point of reference.

The possible effects should be studied by stimulation of the large scale variations in a small scale experimental set up. Limiting factors (e.g. mass transfer) are scaled down and can be studied and maintained in an economical way.

For the production of desired amount of metabolites, some of the calculations are very useful. For example, genetically engineered E. coli at 1.5 g/L of cell concentration produces 150 mg/L of insulin.

What would be the volume of fermentor to get 1.5 Kg of insulin at: (i) 1 g/L of cell concentration and 150 mg insulin production from g”¹ of cells, (ii) 25 g/L of cell concentration and 150 mg insulin production per g”¹ of cells, and (Hi) 25 g/L of cell concentration and 500 mg insulin production per g~’ of cells.

i. Insulin yield per liter is 1 x 150 = 150 mg/1. For production of 1.5 Kg (=15,00,000 mg) of insulin the volume of fermentor required will be 15,00,000/150=10,000 L.

ii. Insulin production per litre is 25 x 150 = 3,750 mg/L. For the production of 1.5 Kg (15,00,000 mg) insulin the volume of fermentor required will be 15,00,000/3,750=400 L.

iii. In third case cell concentration (25g/L) and insulin concentration (500 mg/g) are very high. At such condition insulin production per litre is 25 x 500 = 12,500 mg/L. For the production of 1.5 Kg (15,00,000 mg) insulin the volume of fermentor required shall be 15,00,000/12,500 = 120 L.

The desired microorganism can be used directly for production of products. Because there are several risks associated with economics, production and quality of products. There must be more benefits on small investments but not vice versa.

The laboratory processes need to be validated in laboratory at intermediate stage in a pilot plant. The pilot plant acts as a small model of commercial plant.

The results obtained from pilot plant are very useful in setting up a commercial scale plant. For setting up a commercial plant the capital investment is required in many areas such as design and construction of fermentor, utilities (e.g. steam water, electricity fitting, other infrastructure), manpower (technical and non-technical) and marketing.

The results obtained from a pilot plant are theoretically extrapolated and applied for commercial plants too as far as capital investments are concerned. Finally, a techno-economic report is prepared based on the above data of capital investment. On the basis of these reports banks finance for establishment of commercial scale plant.