Which of the following is not a part of downstream processing?

The correct answer is Option (4) → Biosynthesis

Downstream processing is the series of steps a product goes through after it has been made in the bioreactor, before it can be marketed.

Option (1) Separation — A part of downstream processing. The product is first separated from the cells and the culture medium.

Option (2) Purification — A part of downstream processing. The separated product is then purified; separation and purification together are what NCERT calls downstream processing.

Option (3) Quality control — A part of downstream processing. The formulated product undergoes strict quality control testing before it is sold.

Option (4) Biosynthesis — Not a part of downstream processing. Biosynthesis is the making of the product by the cells inside the bioreactor. It is the stage that comes before downstream processing.

NCERT Extract:
Downstream Processing – “After completion of the biosynthetic stage, the product has to be subjected through a series of processes before it is ready for marketing as a finished product. The processes include separation and purification, which are collectively referred to as downstream processing. The product has to be formulated with suitable preservatives. Such formulation has to undergo thorough clinical trials as in case of drugs. Strict quality control testing for each product is also required.”