Bioethanol Production Using Mixtures of Sorghum Juice and Sugarcane Molasses: Experimental Data and Kinetic Modeling

In Brazilian distilleries, bioethanol is mainly produced using musts obtained from sugarcane, with production restricted to the sugarcane harvest period. The present work evaluated ethanol production using fermentation musts prepared from a mixture of sorghum juice and diluted sugarcane molasses, with the aim of shortening the off-season of ethanol production. Firstly, kinetic modeling of ethanol fermentation was performed employing musts prepared solely with diluted sugarcane molasses and sweet sorghum juice. Subsequently, ethanol fermentations were carried out with musts prepared by mixing diluted sugarcane molasses and sweet sorghum juice in different proportions. The hybrid Andrews-Levenspiel model provided excellent fits to the experimental data for the fermentations performed with the individual musts. In all the fermentations with mixed musts, there was faster substrate uptake and earlier substrate exhaustion, compared to the fermentation using only diluted sugarcane molasses. The fermentation initiated with a mixture of 25% diluted molasses and 75% sweet sorghum juice resulted in around 17% higher ethanol productivity (in units of g L-1 h-1), compared to the fermentation with sugarcane molasses alone.