Kinetic modeling of batch bioethanol production from CCN-51 Cocoa Mucilage

Background: The aim of this study was the production of bioethanol generated during the fermentation of CCN-51 Cocoa mucilage with Saccharomyces cerevisiae yeast and the fitting of experimental data to the mathematical models: Logistic, modified Gompertz, and Andrews and Levenspiel. There are limited studies regarding the high energy potential of cocoa mucilage from Ecuador for bioethanol production as a gasoline additive. Currently, this by-product of the cocoa industry is considered as waste. Methods: Discontinuous fermentation was performed in a batch bioreactor under different conditions of pH, temperature and yeast concentration. During the reaction, bioethanol concentration, yeast and consumed substrate were evaluated by means of microdiffusion, dry weight by lyophilization and UV spectrophotometry, respectively. Significant Findings: The result of the final bioethanol concentration was 25.41 g/L at a temperature of 35 °C, pH of 4 and yeast concentration of 3 g/L. The models were fitted with determination coefficients greater than 0.9. From the results, the logistic model was used to describe yeast growth. Modified Gompertz model is considered appropriate for modeling bioethanol production. Both models fit the data adequately; however, Andrews and Levenspiel model, besides of the good adjustment, considered inhibition terms of the substrate and product.