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 (C
E0) 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 (C
E0) 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.