Abstract: The invention relates to a method for treatment of the biomass. The crude biomass is hydrolyzed by means of a proteolytic enzyme, the dissolved hard particles are separated from the total hydrolyzate by rough filtration, and the filtrated enzymatic hydrolyzate is submitted to membrane separation through semipermeable membranes.All of the steps are carried out at mild operating conditions, which preserves the structure and composition of the nonproteinic compounds. The use of organic solvents is entirely avoided, resulting in a safer process. The available proteins are extracted from the total mass as a protein hydrolyzate, which is easily digested. The final product yield is 92-95% amino acids. Gel chromatographic analysis of the final product shows that the free amino acids and the peptides have a molecular weight of 1000 to 4000 Daltons.