NOVELTY - Obtaining polysaccharide-rich composition comprising beta-glucan, chitin and chitosan extracted from cell wall of Saccharomyces cerevisiae from biomass by-product resulting from beer production method, involves: (i) preparing a reactor with a solution of sodium hydroxide (NaOH); (ii) adding the resulting biomass to the solution; (iii) maintaining conditions for at least 1 hour; (iv) cooling the solution to room temperature; (v) neutralizing the solution; (vi) separating the solid product; (vii) subjecting the solid product to washing with water; and (viii) drying the solid product.    USE - The method is useful for obtaining polysaccharide-rich composition comprising beta-glucan, chitin and chitosan extracted from cell wall of Saccharomyces cerevisiae from biomass by-product resulting from beer production method. The composition is useful for preparing pharmaceutical and/or veterinary medicine and edible product (e.g. dietary supplement). It can also be used as preventive and/or therapeutic agent; used as ligand of fat in intestine agent; and used for preventing and/or treating a disorder selected from overweight, obesity, hypercholesterolemia, hypertriglyceridemia, hypertension and cardiovascular disorders (all claimed).    ADVANTAGE - The composition provides desired active agent benefit, but low enough to avoid serious side effects in the medical judgment.    DETAILED DESCRIPTION - Obtaining polysaccharide-rich composition comprising beta-glucan, chitin and chitosan extracted from cell wall of Saccharomyces cerevisiae from biomass by-product resulting from beer production method, involves: (i) preparing a reactor with a solution of sodium hydroxide (NaOH) at a concentration of 0.25 to 3 M, with stirring and a temperature between 50 and 95 degrees C; (ii) adding the resulting biomass to the solution; (iii) maintaining conditions for at least 1 hour; (iv) cooling the solution to room temperature; (v) neutralizing the solution with at least one addition of acidic water or solution, until pH is 7 where when more than an addition is made, a step of separating the solid product from the solution between additions is performed; (vi) separating the solid product obtained from step (v) of the solution; (vii) when the neutralization step (v) is made by adding an acid solution, the solid product is subjected to at least one washing with water and separating the solid product obtained; and (viii) drying the solid product to a constant weight, and micronizing. INDEPENDENT CLAIMS are:    (1) composition obtainable by the method;    (2) pharmaceutical and/or veterinary medicine comprising the composition together with appropriate pharmaceutical or veterinary acceptable excipients; and    (3) edible product comprising an effective amount of the composition together with appropriate amounts of other edible ingredients.