Dynamic Modelling and Simulation of Citric Acid Production from Dilute Acid Hydrolysed Corn Starch Using Aspergillus Niger

Abstract

The modelling of batch production of citric acid from corn starch hydrolysate using Aspergillus niger ATCC 9142 was carried out in this work. A validated mathematical model was developed to describe the process. Four kinetic models, Monod, Haldane, logistic and hyperbolic for simulating the growth of the Aspergillus niger cells were explored. The validity of the models in terms of predicting the growth of Aspergillus niger cells was determined by fitting each kinetic model to experimental data. Comparison of experimental results to model predicted results revealed 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 were 0.0130h-1, 0.711g/g, 13.671g/g, 0.001g/L, and 0.257 g/L respectively. Results of simulating the model showed that the production of citric acid was a growth associated process.  Optimum pH, initial sugar concentration and temperature for citric acid production obtained were5.5, 40w/v and 30oC respectively.http://dx.doi.org/10.4314/njt.v33i2.12