Abstract: This application concerns a method for preparing glucan from Aspergillus niger, characterised in that it comprises (i) the at least partial deacetylation of the mycelium of A. niger; (ii) acid treatment of the (partially) deacetylated mycelium, preferably following purification and/or washing, to obtain insoluble glucan and soluble chitosane, which acid treatment comprises placing the deacetylated mycelium in contact with an acidic solution; (iii) the separation of the soluble chitosan on the one hand, and the insoluble glucan on the other; (iv) alkaline treatment of the glucan comprising placing the glucan in contact with an alkaline solution to cause the glucans to flocculate; and (v) drying the flocculated glucans to obtain glucan powder. This invention further concerns the glucans thus obtained, compositions comprising them, and their uses. The glucans of the invention may be used as immunostimulants.