Bioprocess for Xylitol from Hemicellulose

When ethanol is produced from corn, only the starch is transformed, and a significant amount of byproducts is produced. If these byproducts, which are rich in sugars, could be made into a valuable product, the cost-effectiveness of ethanol production will be enhanced. One such potential product is xylitol, a five-carbon polyalcohol that has gained acceptance as a natural food sweetener that can replace sucrose on a weight-for-weight basis. Although xylitol is in high demand by the food ingredient and confectionary industries, its use currently is constrained by the limited supply of raw materials. This project will develop a bioprocess to transform waste sugars into xylitol, thereby improving the economics of ethanol production. In Phase I, bacterial host strains were developed for the transformation of these waste sugars. In addition, the various feedstocks that would feed the bioprocess were evaluated, several prototype bioconversion systems were assembled and tested, and some preliminary metabolic engineering was performed to demonstrate feasibility. Phase II will involve further metabolic engineering, fine-tuning of the fermentation process, and scaling-up the process to commercial levels. Commercial Applications and other Benefits as described by the awardee: The new bioprocess should significantly reduce the cost of commercial xylitol production, free xylitol production from the current raw-material-availability constraints, and have a positive impact on the economics of fuel ethanol production. Moreover, domestic firms would be able to produce xylitol more cheaply, thereby avoiding the need to relocate manufacturing facilities to Southeast Asia. Finally, the new bioprocess should be inherently cleaner and safer than the existing hydrogenation process for xylitol.