A mathematical model for the growth of Aspergillus niger in a solid-state fermentation.
Integration of life sciences & engineering
Design, Analysis & Control of Fermentation Processes (T5-2)
Keywords: Aspergillus niger, solid-substrate fermentation, fungal radial growth, mathematical model, morphometrical parameters.
Aspergillus niger is an important mould for the production of citric acid that grows in liquid as well as in solid state fermentation (SSF). The former presents serious limitations when substrate concentration (glucose) is above 50 g/L, however this is not the case in SSF where this fungi can grow on glucose concentration up to 250 g/L. To study the radial growth of a colony of A. niger in SSF, an experimental and theoretical work has been performed, and a mathematical model for this has been developed. The model accounts for a modified Monod kinetics and describes mass transport by diffusion through the solid substrate as well as within the colony and fungal growth as a moving boundary. Experiments were carried out in a Petri dish, using different glucose concentration (50- 250 g/l), as carbon source, the radial growth of the A. niger was measured at different periods in time, and in all cases the morphometrical parameters: diameter and average length of the hypha (dh, Lav) were measured by image analysis. Model simulations in the range of glucose concentration used in this study showed good agreement with experimental data, which allowed the estimation of the kinetic parameter in the Monod expression (µmax), and was used to infer the axial and radial glucose concentration gradients within solid medium. The results of the simulations suggest that the growth is affected by the glucose concentration, and the morphometrical parameters have a direct relation with µmax.
Presented Thursday 20, 11:00 to 11:18, in session Design, Analysis & Control of Fermentation Processes (T5-2).
