Single Cell Protein (SCP)

Single Cell Protein (SCP) is simply the dried cell mass of microorganisms - bacteria, fungi or algae - harvested and used as a protein-rich food or feed supplement, rather than any single defined protein molecule. The appeal is straightforward: SCP organisms are genuinely nutrient-dense (high in protein, vitamins, essential amino acids and lipids) and can, in principle, be produced in bulk from cheap or even waste substrates, offering a partial answer to global protein scarcity. The catch is that SCP's high nucleic-acid content and comparatively slow digestibility have kept it from ever fully displacing conventional protein sources. The organisms actually used span all three microbial kingdoms - bacteria such as Methylophilus methylotrophus, Cellulomonas and Alcaligenes; fungi such as Agaricus campestris, Saccharomyces cerevisiae (ordinary baker's/brewer's yeast) and Candida utilis; and algae such as Spirulina, Chlorella and Chlamydomonas. Spirulina in particular can be cultivated on genuinely low-value inputs - potato-processing wastewater, straw, molasses, animal manure, even raw sewage - turning what would otherwise be pollution into a protein-rich product, which is a real environmental co-benefit on top of the nutritional one; a mere 250 g of Methylophilus methylotrophus, thanks to its very high growth rate, can be scaled up to yield 25 tonnes of protein. Its real-world uses go well past food: it is …