Method for enriching a biomass with proteins

A process for producing a protein-rich biomass and removing glycogen from a biomass of lysed microorganisms that accumulate water-soluble glycogen during their growth selected from unicellular red algae (URA) of the genera Cyanidioschyzon, Cyanidium and Galdieria, wherein the process comprises the steps of:

• a) lysis of a biomass of microorganisms,
• b) suspending and acidifying the biomass of step a), wherein the suspension and the acidification consists in:
• b1) suspending the biomass of lysed microorganisms obtained in step a,
• b2) acidifying the suspension of step b1 to a pH less than or equal to 5,
• wherein steps b1) and b2) are simultaneous or consecutive, when b1) and b2) are consecutive step b2) being carried out directly after step b1) without any further biomass treatment step;
• and
• wherein the acid suspension obtained in step b2) has a dry matter content from 3 to 30%, and
• c) recovering the lysed biomass fraction insoluble at pH less than or equal to 5, wherein the recovered lysed biomass has a glycogen content of less than 10% in relation to the dry matter, and wherein an increase of the protein content of more than 14% in the recovered lysed biomass is obtained relative to the protein content of the lysed biomass in step a);
• wherein the process does not comprise a defatting step.