Kinetic model of ethanol inhibition for Kluyveromyces marxianus CCT 7735 (UFV-3) based on the modified Monod model by Ghose & Tyagi

Ethanol tolerance is one of the main limiting factors for scaling up its production. Bioprocess control can be performed by knowing the ethanol effects on cell growth, since it is a product associated with microbial growth and, therefore, its synthesis depends on the specific cell growth rate (µ). In this study, mathematical modeling based on the integration of effects was used to develop an ethanol inhibition model for Kluyveromyces marxianus CCT 7735 (UFV-3), at different ethanol concentrations, using glucose as a limiting substrate. A modified Monod model based on studies by Ghose & Tyagi was designed. This model was able to describe with high accuracy the µ parameter behavior as a function of sub-inhibitory glucose concentrations (R²=0.992), and inhibitory ethanol conditions (R²=0.999). The proposed model presented µ max = 0.673 h − 1 , K S = 0.997 g.L − 1 , and P crit = 6.78 % (v/v), whose validation had a mean error of 7.43 %. The µ parameter was mainly influenced by ethanol, showing a linear reduction with the ethanol increase in the culture medium, while glucose concentrations above 20 g.L − 1 had little influence on its value. Therefore, using a simple methodology, an efficient ethanol tolerance model was proposed, which can contribute to future studies of large-scale fermentation using K. marxianus strains.