Oxalic acid is the simplest organic dicarboxylic acid. At the same time, it is a very common plant acid. Despite its toxic properties, it is used in the food industry as an agent to inhibit enzymatic browning of fruits, as a stabilizer to improve the aroma of food products, and as a clarification agent. Owing to the increasing amounts of waste glycerol produced during the production of bio diesel, there are more and more researches into the application of this waste product as a source of carbon in biotechnological processes. The objective of this paper was to study the possibility of utilizing glycerol as a source of carbon and energy in the oxalic acid biosynthesis process by Aspergillus niger W78C in the shaking flasks-based cultures, as well as to determine the optimum concentration of macro-elements in the medium applied in the process. In the biosynthesis process, glycerol appeared to be a good source of carbon and energy in the bioproduction of oxalic acid. The best bioprocess results, more than 43 g dm-3 of oxalic acid, were obtained in the variant of the medium containing: 1.30 g dm-3 NH4NO3, and 0.3 g dm-3 of KH2PO4 and MgSO4·7H2O. The lack of phosphorus in the medium was a critical factor as regards the growth of biomass, and this fact significantly limited the production of oxalic acid. Nitrogen was found to be, also, an important component of the medium. The culture developed in the variant with a too low concentration level of this element (0.12 g NH4NO3 dm-3) was characterized by a low growth level of biomass and by low values of the product concentration. The presence of magnesium salt was not critical for the process to run. The lack of this component limited the increase in the growth of this product by ca. 2 g dm-3.
oxalic acid, Aspergillus niger, bio-synthesis, glycerol, biodiesel