Kinetic Models for Citric Acid Production

Although the citric acid is one of the oldest biotechnology products, the abundance of possible raw materials and microorganisms which could process those substrates made very difficult the possibility of finding a general kinetic for this biological process. Furthermore, the cross inhibition of both substrate and product and the capacity of the microorganisms to switch from regular carbon-based substrates to citric acid as substrate, ceasing its production, when the former vanished from the bioreactor add great challenges to finding a useful kinetic model. The aim of the paper is to propose and analyse several improved kinetic models for the process of citric acid fermentation, based upon published experimental data, on one hand, and the qualitative opinions related to inhibition found in literature, on the other. According to the considered substrat, the best model minimizing the usual sum of squared residuals model - experiment was chosen.