A solid state fermentation method was developed for citric acid production from different substrates by culturing Aspergillus niger S. A Sugar beet pulp was applied as the main substrate; it was enriched by raw materials such as: tapioca, beet or cane molasses, com starch, wheat bran, and potato waste pulp. The yield of citric acid varied depending on the type of different substrates added; it ranged from 68 g/kg d.s. for wheat bran added, to 160 g/kg d.s. as for potato waste pulp, and up to more than 200 g /kg d.s. as for the addition of tapioca and cane molasses.