Submerged production of oxalic acid from glucose by immobilized Aspergillus niger

Oxalic acid is now considered as a useful chemical in various hydrometallurgical processes. For its massive applications in hydrometallurgy, cost-effective production of the acid is necessary. In this direction, fermentative production of the acid from glucose appears attractive. Aspergillus niger, the main oxalic acid producing organism, in general oxidizes glucose rapidly to gluconic acid, and conversion of this sugar to oxalic and citric acid is always sufficiently less. In this article, we have shown that immobilized mycelia (bioparticles) of A. niger NCIM 548 strain secreted more oxalic acid from glucose than the amounts produced from either sucrose, lactose or glucose under submerged condition. Germination of immobilized spores in polyurethane foam yielded bioparticles which produced more (average: 3-fold on 7th day and 3.7-fold on 9th day) oxalic acid from glucose compared to free mycelium cells, mainly during the 2nd and 6th cycle. Recycled bioparticles maintained average activity of acid production up to six cycles.