SIMULATION OF GLUCONIC ACID PRODUCTION FROM GLUCOSE IN AN AIRLIFT BIOREACTOR

Abstract

A mathematical model for the prediction of performance of a bioprocess of gluconic acid production in an airlift bioreactor (ALBR) in a batch process has been developed. The model consists of a set of simultaneous first order ordinary differential equations obtained from material balances of cell mass (X), product (P), substrate (S) and dissolved oxygen (Co) around the hypothetical well mixed stages in the bottom, riser, top and down corner sections of an ALBR. Logistic equation and contois model constitute the kinetic part of the main model and are incorporated through material balance. These equations are solved using ODE solver of MATLAB (Version 6.5). Equations similar to Leudeking-Piret, which combine growth and non-growth associated contributions are used for the representation of biomass, product, substrate and dissolved oxygen with time. The kinetic parameters of logistic equation are extracted by non-linear regression using GraphPad (Version 4.03) software. Logistic and contois models are compared for prediction of time dependent concentration profiles of biomass, gluconic acid, glucose and dissolved oxygen (DO) in an ALBR. Validated logistic and contois models are used to predict the effect of change in initial biomass concentration (X0) and airflow rate (Qg), respectively, when these parameters are varied from their mean values, on the performance of gluconic acid production in ALBR. An airlift bioreactor of 4.5 1 working volume was designed and developed for further experimental investigation of the bioprocess. It was concluded that the mathematical model incorporated with multi-kinetic models would be more efficient to study the overall biotechnological process. The model is simple enough to be used in design studies and it can be adapted to airlift system configurations and fermentation systems other than gluconic acid.