Support based on organic and/or inorganic fibres covered at least on one of the faces thereof with a chitosan-based layer, characterized in that the layer is obtained by depositing a chitosan-based aqueous solution, the average molar mass of which has a mass less then 130 000 g/mol, the concentration of which is between 6 and 30% by weight and the viscosity of which is between 100 and 3000 cps.