This document discusses microbial protein supplements (SCP) which are dried cells of microorganisms that can be used as dietary protein. It provides the average compositions of proteins, fats, nucleic acids and other components of common microorganisms used for SCP, including fungi, yeast, algae and bacteria. The document also briefly discusses immobilized enzyme systems and methods of enzyme immobilization such as entrapment, adsorption, ionic binding and cross-linking to restrict enzyme mobility.