Method for extracting soluble proteins from microalgal biomass

A method for preparing a protein isolate from the biomass of microalgae of the Chlorella genus, comprising:

• providing a microalgal biomass produced by fermentation of microalgae of the Chlorella genus, wherein the fermentation is carried out for more than 36 hours at 28° C. with agitation and at a pH of 6.5,
• washing the microalgal biomass so as to eliminate interstitial soluble compounds and concentrate the microalgal biomass,
• mechanical milling of the washed and concentrated microalgal biomass, carried out in a horizontal bead mill type system, to obtain an emulsion,
• destructuring the obtained emulsion by (i) or (ii), thus resulting in a destructured emulsion:
• (i) by enzymatic predigestion, by treatment with polar solvent, and/or by controlled alkaline treatment targeting the protein fraction of the emulsion for a duration of 2-8 hours at a temperature of more than 30° C. and a pH of greater than 7;
• or
• (ii) by treatment with a polar solvent, and/or by enzymatic digestion targeting the interface with the lipid fraction of the emulsion for a duration of 6 hours at a temperature of 50° C. and a pH of 5-6;
• triphase separation so as to separate the soluble fraction from the fractions containing lipids and cell debris,
• recovering the soluble fraction obtained in this way in order to obtain the soluble protein isolate, then
• evaporation, pasteurization and atomization of the protein isolate.