Different types of microbes, such as bacteria, fungi, moulds,
algae and yeasts, can be used as sources of SCP. Algal single-cell
protein has limitations, such as the need for warm temperatures,plenty of sunlight and carbon dioxide; the algal cell wall is indigestible.
Bacteria are capable of growing on a wide variety of substrates,
have a short generation time and possess a high protein
content. Their use is somewhat limited by the generally poor public
acceptance of bacteria as a food, their small size and difficulty in
harvesting and the high content of nucleic acid on a dry weight
basis. Yeasts are probably the most widely accepted and utilised
microorganisms for single-cell protein production; thus it will be
beneficial to focus on yeast single-cell proteins rather than on bacterial
and algal single-cell proteins