Assessment of Aspergillus niger biofilm growth kinetics in minibioreactors by carbon dioxide evolution

Aspergillus niger ATCC 10864 was grown on bubble minicolumns aerated with pure oxygen either as biofilm or free-mycelium submerged systems. Growth kinetics was followed by estimating biomass from released carbon dioxide using a titration method and mathematical models. Submerged cultures showed increased endogenous respiration rates (0.0298 vs. 0.0004 g biomass/g biomass.h) possibly related to stress condition since this type of growth is not the natural way of life of A. niger. On the other hand, A. niger biofilm growth followed a logistic model having higher maximal specific growth rate than submerged cultures (0.061 vs. 0.045 h-1). This may be related to better mass transfer processes due to a channeled mycelial microstructure. Biofilm growth can be easily and reliable assessed by evaluating the CO2 released during the fermentation in minibioreactors.Key words: Aspergillus niger, biofilm, mathematical modeling, endogenous respiration, Cryo-SEM