Integrated Process Combining High-Temperature Fermentation and Extractive Ethanol Removal via CO<sub>2</sub> Stripping
Jorge Luíz Silveira Sonego | Jaqueline Machado de Moraes | Nayana Simon de Vargas | Anderson Ferreira da Cunha | Rosineide Gomes da Silva Cruz | Antonio José Gonçalves Cruz | Alberto Colli Badino
Fermentation at high temperatures may be a viable alternative for ethanol production, especially in tropical climate regions. This work describes the evaluation of ethanol production through extractive fermentation at high temperatures using thermotolerant <i>Kluyveromyces marxianus</i>. An experimental design was applied to assess the effect of temperature on the ethanol removal process by CO<sub>2</sub> stripping. Subsequently, kinetic modeling of conventional batch ethanol fermentation at high temperatures was performed, and the hybrid Andrews−Levenspiel model was found to be suitable for describing the kinetics of this process. Experiments were conducted to evaluate ethanol production at high temperatures using thermotolerant yeast, specifically evaluating the effects of different specific CO<sub>2</sub> flow rates (ϕ = 1.0, 1.5, and 2.0 vvm) on ethanol stripping. The results indicated that in all the extractive fermentations conducted with <i>K. marxianus</i>, there was faster substrate uptake and earlier substrate exhaustion compared to conventional fermentation. Significant ethanol removal by stripping was achieved using a CO<sub>2</sub> flow rate of 1.0 vvm (EF<sub>HT</sub>1), and complete substrate consumption was observed by the end of 12 h of fermentation. This result highlights the positive effect of temperature on ethanol entrainment. In addition, integrating the CO<sub>2</sub> stripping technique with high-temperature fermentation (T = 40 °C) improves process efficiency with a lower gas flow rate. This is advantageous, especially for industrial-scale applications, as it can reduce equipment costs associated with the CO<sub>2</sub> feed.
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