Modelling and Simulation of Citric Acid Production from Corn Starch Hydrolysate Using Aspergillus Niger

Abstract

The kinetics of citric acid fermentation from corn starch hydrolysate using Aspergillus niger ATCC 9142 was studied in a batch fermenter. A general model for citric acid production was formulated. Four kinetic models, Monod, Haldane, logistic and hyperbolic for describing the growth of the fermenting microorganism were explored. The validity of the models in terms of predicting growth of the fermenting organism was determined by fitting each kinetic model to experimental data collected in the course of this work. Comparison of experimental results to model predicted results showed that only the hyperbolic model was able to accurately replicate the experimental results. This was evident from the high level of correlation between the experimental and model predicted results. The kinetic parameters for cell growth, substrate consumption and product formation µmax, Yx/s, Yp/x, Ks and Kp as calculated by the hyperbolic model are 0.01320h-1, 0.711g/g, 13.6708g/g, 0.0006g/dm3, and 0.2572 g/dm3 respectively. The validated model was implemented in an advanced equation oriented modelling software to determine the effect of key process parameters on the production of citric acid. Results of simulating the model show that the production of citric acid is a growth associated process. Optimum pH, initial sugar concentration and temperature of for citric acid production were 5.5, 40w/v and 30oC respectively