Very-high-gravity (VHG) continuous fermentation with yeast recovery, activation and recycle fermentation for ethanol production from sugarcane

VHG continuous fermentation technology was developed to produce ethanol from sugarcane aiming to increase global mill efficiency, minimize effluent (vinasse) disposal and expand the electric potential. The development was based on the conceptual engineering design which included the following main assumptions: distributed carbon source feeding, temperature setup according to the Arrhenius equation to avoid inhibition by ethanol, intracellular detoxification through a second centrifugation and yeast treatment step to promote its membrane recovery and enzymatic restoration. The yeast treatment and the fermentation setup were performed in a bench-scale fed-batch system to obtain validated operating protocols to scale up the process to a pilot unit. The results showed that the novel process could significantly contribute to improving the industrial efficiency through an increase of productivity of up to 9 g ethanol / L. h, which is about double of the current productivity. This is due to the increased ethanol titer, from the current 8.5°GL to 15°GL. As a result, there is a reduction of vinasse disposal and steam demand to distillation system.