Modeling of caffeine degradation kinetics during cultivation of Fusarium solani using sucrose as co-substrate.

Microbial kinetics for simultaneous caffeine degradation and its biotransformation to
theophylline has been investigated using Fusarium solani. Caffeine was utilized by the fungus as
a sole nitrogen source in the presence of sucrose, which served as the primary carbon source. A
reaction mechanism involving Monod kinetics with both substrate and product inhibition was
formulated based on experimental evidence. A total of thirteen kinetic parameters were involved
in the model formulation and these were estimated using a simulated annealing algorithm.
Moreover, the parameter estimation was carried out for three different experimental sets
simultaneously with varying initial sucrose concentration, in order to obtain a common set.
Based on sensitivity analysis, among thirteen parameters, saturation constant of biomass
accumulation from sucrose utilization ( s1 K ), yield of biomass from sucrose utilization (
X2 / X1 Y ),
lumped parameter which was defined as apparent yield of biomass from caffeine degradation
process ( X 2/ X 3 Y ), and yield of theophylline from caffeine metabolism (
X4 / X3 Y ), were observed to
be highly sensitive. The experimental results were in good agreement with the model predictions
and have also been validated for an experimental setup which was not used for calibration. The
results of the present study has potential application in the development of a process for
detoxification of caffeine containing wastes as well as for production of a value added product
theophylline.