Q.Define Single Cell Protein (SCP), naming one organism commonly used to produce it.

Correct answer: (a) Spirulina spp.

Spirulina is a cyanobacterium (blue-green alga) widely cultivated as a single-cell protein source; the others listed are fungi/yeast.

Among the given options, Spirulina spp. is a photosynthetic, filamentous cyanobacterium (blue-green alga), commercially cultivated as a rich source of single-cell protein (SCP) and nutritional supplements due to its high protein, vitamin and mineral content. Aspergillus niger and Trichoderma viride are filamentous fungi (used respectively in citric acid production/industrial enzyme …

Because microbes multiply and synthesise protein far faster than livestock, growing microorganisms in bulk purely as a protein source is called Single Cell Protein (SCP).

The data given makes the point vividly: a 250 kg cow produces only about 200 g of protein per day, whereas in the same period just 250 g of the bacterium Methylophilus methylotrophus can produce 25 tonnes of protein. This enormous difference arises because microorganisms have extremely fast generation/growth rates and can be cultured on a large industrial scale using cheap substrates (e.g. molasses, whey, agricultural or industrial waste), so their biomass — and hence their protein content — accumulates far more quickly and efficiently, per unit of starting mass and time, than any animal ever could.

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