SYSTEMS AND PROCESSES FOR ENHANCED YIELD FROM FERMENTATIONS THAT CONTAIN XYLOSE

摘要

A system and process for the utilization of xylose during fermentation is described. The system uses a fermenter and a separate reactor to isomerize the xylose to xylulose. The separation of the two processes allows the optimization of each process since the isomerization operates ideally in a calcium free environment near pH 7.5 while the fermentation operates ideally below a pH of 6. Control of pH is assisted by the modulation of CO2 in the fermentation medium. Xylulose is fermented to ethanol by numerous standard yeasts although other products are also possible. The separate reactor may be run in a single pass, or, more preferably in a recirculating mode to allow full isomerization while the xylulose product is being consumed by the yeast. A preferred embodiment includes a Simultaneous Saccharification and Fermentation system where the liquid portion of the fermenting broth is isomerized and returned to the fermentation vessel.