Question

Upstream and downstream processing in fermentation

Answer 1

the upstream process is defined as the entire process from early cell isolation and cultivation ,to cell banking and culture expansion of the cell until final harvest. the downstream of a bioprocess refers to the part where the cell mass from the upstream are processed to meet the purity and quality requirements

Answer 2

Depending on the circumstance, the termfermentation can have three meanings. In a physiological sense, fermentation refers to a process that produces energy by breaking down of energy-rich compounds under anaerobic conditions. This is the basis of food fermentation, which is commonly used in the food industry in order to produce diverse food products and also as a food preservation method. In a biotechnological contextthough, this term is used in a much broader sense. There, fermentation means a process in which microorganisms that are cultured on a large-scale under aerobic or anaerobic conditions, convert a substrate into a product which is useful to man.

Basic Steps of Industrial Fermentation

Any industrial fermentation operation can be broken down into three main stages, viz, upstream processing, the fermentation process and downstream processing.

Upstream processing includesformulation of the fermentation medium, sterilisation of air, fermentation medium and the fermenter,inoculum preparation and inoculationof the medium. 

The fermentation medium should contain an energy source, a carbon source, a nitrogen source andmicronutrients required for the growth of the microorganism along with waterand oxygen, if necessary.

A medium which is used for a large scale fermentation, in order to ensure the sustainability of the operation, should have the following characteristics;
1. It should be cheap and easily available
2. It should maximise the growth of the microorganism, productivity and the rate of formation of the desired product
3. It should minimise the formation of undesired products 

Usually, waste products from other industrial processes, such as molasses, lignocellulosic wastes, cheese whey and corn steep liquor, after modifying with the incorporation of additional nutrients, are used as the substrate for many industrial fermentations.

Sterilisation is essential for preventing the contamination with any undesired microorganisms. Air is sterilised by membrane filtration while the mediumis usually heat sterilised. Any nutrient component which is heat labile is filter-sterilised and later added to the sterilised medium. The fermenter may be sterilised together with the medium or separately.

Downstream Processing includes therecovery of the products in a pure state and the effluent treatment. Product recovery is carried out through a series of operations including cell separationby settling, centrifugation or filtration;product recovery by disruption of cells (if the product is produced intracellularly);extraction and purification of the product. Finally, the effluents are treated by chemical, physical or biological methods.