Continuous 2G ethanol production from xylose in a fixed-bed reactor by native Saccharomyces cerevisiae strain through simultaneous isomerization and fermentation

Abstract

The yeast Saccharomyces cerevisiae is the most used microorganism for ethanol production, however, on its wild form it cannot assimilate xylose. The previous ex-vivo isomerization of xylose to xylulose catalyzed by the enzyme xylose isomerase (XI) is an alternative to overcome this limitation. The present work evaluated continuous 2G ethanol production through xylose simultaneous isomerization and fermentation (SIF) using xylose isomerase co-immobilized with yeast. From the initial studies carried out with five different industrial S. cerevisiae strains, Itaiquara® baker´s yeast was selected due to its good performance in terms of ethanol yield (0.34 g/g) and productivity (2.1 g/L/h) having xylose as a carbon source. Continuous xylose SIF in a fixed-bed reactor was run for 7 days with high values of ethanol yield (0.37 g/g) and productivity (1.9 g/L/h). The operation for longer periods could be possible upon implementing strategies for pH and contamination control, showing great progress to achieve a feasible industrial 2G ethanol production process.