This SBIR Phase II project will develop a method to convert the byproduct glycerol to a value-added co-product, xylitol, thereby helping to reduce the costs associated with biodiesel production. The anticipated result is a scalable process capable of converting crude glycerol to xylitol in a single step bioreactor process and a demonstrated method for recovery of the value-added product.
The broader impact/commercial potential of the project will be to further biodiesel as a replacement for petrochemical diesel. Converting the main by-product of biodiesel production, glycerol, to a value-added product would improve the economics of biodiesel, while removing a waste stream and providing a reduction in price of the co-product. Xylitol itself also has beneficial societal impacts including anti-carcinogenic effects as a safe sweetener for diabetics, and it does not promote new cases of diabetes as some sweeteners are suspected of doing.
This project was aimed at developing methods to utilize biofuel waste streams to produce the co-products that could help drive the economics of biofuel production. In this project we demonstrated that glycerol, a by-product of biodiesel production, can, with only minimal purification, be used by E coli as a carbon source. Additionally, we have constructed an E coli strain that can convert simple sugars such as glycerol, glucose or gluconate, to more valuable 5-carbon compounds, improving the economics of biodiesel production. In particular, one compound that we developed a production process for is xylitol, a reduced calorie anticariogenic sweetner with known health benefits. This process will provide an alternative to the current xylitol production process which involves expensive and environmentally unfriendly extraction of xylose from birch trees followed by chemical conversion. More than 20 new bacterial strains with various combinations of deleted and/or amplified genes in metabolic pathways involving 5-carbon sugars were used to define the best pathway for xylitol production. An additional beneficial outcome of this work was the development of methods for screening large numbers of potentially superior xylitol producers and this method was applied to our ongoing improvements to our proprietary process for making xylitol from xylose.
