A process for the production of .beta.-(1,3)(1,6) glucan from a glucan containing cellular source is described, together with compositions and uses/methods of treatment involving glucan. The process of the invention comprises the steps of: (a) extracting glucan containing cells with alkali and heat, in order to remove alkali soluble components; (b) acid extracting the cells of step (a) with an acid and heat to form a suspension; (c) extracting the suspension obtained of step (b) or recovered hydrolyzed cells with an organic solvent which is non-miscible with water and which has a density greater than that of water separating the resultant aqueous phase, solvent containing phase and interface so that substantially only the aqueous phase comprising .beta.-(1,3)(1,6) glucan particulate material remains; wherein the extraction with said organic solvent provides separation of glucan subgroups comprising branched .beta.-(1,3)(1,6)-glucan, and essentially unbranched .beta.-(1,3) glucan which is associated with residual non-glucan contaminents; and (d) drying the glucan material from step (c) to give microparticulate glucan.