An Evaluation of Mathematical Modeling of Ethanol Fermentation with Immobilized Saccharomyces cerevisiae in the Presence of Different Inhibitors

In ethanol production processes, inhibitors are formed as by-products depending on the raw materials and pretreatments. Inhibitors negatively affect both ethanol yield and biomass growth. This study aimed to examine the influence of inhibitors, including acetic acid (AA), formic acid (FA), and phenol, on ethanol production from the glucose-based medium using immobilized Saccharomyces cerevisiae in a bioreactor. The results showed that the highest ethanol yields and productions were determined as 45.64% and 38.10 g/L, 44.8% and 36.67 g/L, and 44.46% and 39.07 g/L, by the addition of 2.5 g/L AA, 0.5 g/L FA, and 0.5 g/L phenol into the fermentation medium, respectively. Regarding mathematical modeling, the models MGM (AA) and Huang (FA-phenol) were the best models to predict experimental ethanol production. It was determined that the values forecasted with the models MMF (AA-FA) and Weibull (phenol) agreed with the actual biomass growth. Additionally, to forecast the observed values of the substrate consumption, the most suitable model was Weibull (AA-FA-phenol). Consequently, the immobilized-cell ethanol fermentations with inhibitors were successfully performed, and their limit values were determined.