The cultivation of Penicillium strain, isolated from rotten vegetables, on potatoe dextrose broth (PDB) medium enriched in arginine and mineral elements, allowed to obtain a yield of 31.7 mg/g of dry biomass and 9 mg/g of dry biomass into chitin and natural chitosan, respectively. The infrared spectroscopy analysis showed a great similarity between the infrared spectra of chitin and natural chitosan obtained and the commercial chitin and chitosan, respectively.