Modelagem, simulação otimização de biorreator: abordagem para o limite de concentração de substrato na fermentação alcoólica

Abstract

Production of ethanol from sugarcane is a complex biochemical process that plays a vital role in transitioning to cleaner energy sources. Sucrose obtained from sugarcane juice serves as a substrate for fermentation, carried out by the yeast Saccharomyces cerevisiae. This biochemical transformation results in the production of ethanol, a renewable biofuel, and carbon dioxide. In this study, a modeling and simulation of a continuous alcoholic fermentation process from sugarcane using Saccharomyces cerevisiae and its kinetic aspects are conducted, highlighting the importance of optimizing this process due to the need to find alternatives to polluting and nonrenewable fuel sources globally. This work also sought to review the kinetic models of Levenspiel, Monod, and Tosetto, applying them in mass and energy balances for comparison and analysis of the yield and productivity obtained by using each of these models, with varied initial cell concentration, initial substrate concentration, and residence time. Additionally, a model for the ethanol concentration limit, 𝑃𝑚𝑎𝑥, was developed as a function of initial substrate concentration and temperature to make the simulation closer to reality. Factorial designs were carried out, varying residence time, initial substrate concentration, and cells, to compare the influence on yield and productivity results by using a plate heat exchanger with a defined refrigerant fluid flow rate for cooling the bioreactor under the chosen operational conditions. Numerical results revealed significant optimizations, such as a yield of 86.23% and a productivity of 37.90 𝑘𝑔 ℎ −1𝑚−3 with the plate heat exchanger (factorial design 1) for the initial conditions of 14 g/L initial cell concentration, 215 g/L initial substrate concentration, and 2.5 hours residence time, and a yield of 86.28% and a productivity of 42.33 𝑘𝑔 ℎ −1𝑚−3 also with the heat exchanger (factorial design 2) for the initial conditions of 14 g/L initial cell concentration, 215 g/L initial substrate concentration, and 2.5 hours residence time. The simulation was performed based on modeling that purely relied on experimental data and empirical equations taken from the literature, along with some fixed operational conditions as outlined in the research. It underscored the need for further studies to understand other kinetic parameters (beyond the concentration limit of the product analyzed in this study) and their impact on ethanol production.