Optimization of fermentation conditions for gluconic acid production using Aspergillus niger immobilized on cellulose microfibrils

The optimisation of gluconic acid fermentation using immobilized Aspergillus niger on a highly porous cellulose support is described. Experimental results showing the effects of variations in oxygen partial pressure, glucose concentration and biomass concentration have been obtained with a continuous recirculation reactor. Levels of dissolved oxygen and glucose concentrations during fermentation significantly affect the production and fermentation time. The optimum biomass requirement on a porous cellulose support has been estimated to be 0.234 mg cm^?2 for efficient bioconversion. Increasing the quantum of biomass beyond this value resulted in an overgrown biofilm, which affected productivity adversely. Morphological characteristics of immobilized A. niger have also been investigated.