Protein produced by microorganisms, such as algae, bacteria, filamentous fungi, and yeasts, that is extracted for use as a component of human and animal foods. Growing demand for protein is focusing attention both on expanding the range of substrates used to grow the microbial cultures that yield SCP, including food waste and crop residues, and on streamlining production systems for photosynthetic algae that require carbon dioxide and light as raw materials to make SCP.