Identify the organism which is a source of single cell protein and is grown on commercial scale.
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Spirulina
Option (1) Azotobacter — Incorrect. It is a free-living nitrogen-fixing soil bacterium, used as a biofertiliser.
Option (2) Rhizobium — Incorrect. It fixes nitrogen in the root nodules of legumes.
Option (3) Azospirillum — Incorrect. Another free-living nitrogen-fixing bacterium; a biofertiliser.
Option (4) Spirulina — Correct. This blue-green alga is grown on a large scale as single cell protein.
Note: This question is from Chapter 9, Strategies for Enhancement in Food Production, of the pre-rationalised NCERT book. This chapter is not in the present NCERT book (2026-27). The extract below is from the pre-rationalised edition.
NCERT Extract (Pre-rationalised edition, Chapter 9, Strategies for Enhancement in Food Production):
Single Cell Protein (scp) – “… Microbes are being grown on an industrial scale as source of good protein. Blue-green algae like Spirulina can be grown easily on materials like waste water from potato processing plants (containing starch), straw, molasses, animal manure and even sewage, to produce large quantities and can serve as food rich in protein, minerals, fats, carbohydrate and vitamins.”