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Optimization of Fed-Batch Fermentation with in Situ Ethanol Removal by CO2 Stripping
- Sonego, J. L. S., Lemos, D. A., Cruz, A. J. G., Badino, A. C.
- Energy & fuels 2018 v.32 no.1 pp. 954-960
- algorithms, batch fermentation, carbon dioxide, ethanol, ethanol fermentation, ethanol production, fuels, sucrose, sugarcane, vinasse
- One way of overcoming the substrate and ethanol inhibition effects in the industrial ethanol production process is to use fed-batch fermentation coupled with an ethanol removal technique. This work describes the optimization and experimental validation of sugar cane ethanol production by fed-batch fermentation with in situ ethanol removal by CO₂ stripping. The optimization employing a genetic algorithm (GA) was used to find the optimum feed flow rate (F) and the ethanol concentration (CE₀) in the medium at which to initiate stripping, in order to obtain maximum ethanol productivity. Conventional ethanol fermentation employing the optimum feed flow rate was performed with must containing 257.1 g L–¹ of sucrose (180 g L–¹ of total sucrose concentration), resulting in achievement of an ethanol concentration of 82.2 g L–¹. The stripping fed-batch fermentation with high total sucrose concentration (260–300 g L–¹) or 371.4–428.6 g L–¹ in the must feeding was performed with optimal values of the feed flow rate and the ethanol concentration (CE₀) in the medium at which to initiate stripping. At the highest sucrose feed (total concentration of 300 g L–¹), the total ethanol concentration reached 136.9 g L–¹ (17.2 °GL), which was about 65% higher than the value obtained in fed-batch fermentation without ethanol removal by CO₂ stripping. This strategy proved to be a promising way to minimize inhibition by both the substrate and ethanol, leading to increased sugar cane ethanol production, reduced vinasse generation, and lower process costs.