Microbial Biomass- Microbial biomass has been eaten by man since time immemorial either directly as food, e.g., mushrooms, or as a part of the fermented foods. Mushrooms are fruiting bodies of certain basidiomycetous fungi; some of these fruiting bodies are edible, while many are poisonous and nonedible.

In contrast, biomass produced by unicellular and multicellular organisms like bacteria, yeast, filamentous fungi and algae is processed and used as human food or animal feed supplement.

This biomass in called single cell protein (SCP) as it is rich in protein (Ca. 50% on dry weight basis). Both mushrooms SCP are produced on a commercial scale and represent a multi-million dollar annual trade.