Oligosaccharides are molecular recognition elements that play key roles in many vital biological processes such as cell growth and development,and host-pathogen interaction. Among many potential applications, oligosaccharides are particularly promising in diagnostics, vaccine, cancer therapy, prebiotics, and new antimicrobials. Unfortunately, these applications are hindered by the limited scalability and cost-effectiveness of current synthesis technologies. This project develops novel microbial biocatalysts for scalable and cost-effective synthesis of oligosaccharides. The success of this research will not only impact basic research efforts such as the understanding of glycan structure-function relationship, but also will impact broadly on their medical applications, including but not limited to diagnostic cancer diagnostics, vaccine development, prebiotics, and new antivirals.
The goal of this research is to develop novel metabolic engineering strategies for complex oligosaccharide synthesis. Oligosaccharide biosynthesis is particularly difficult due to (i) a high cellular energy demand; (ii) the necessity to engage multiple sugar molecules; (iii) the complexity of the biochemical reaction network. These challenges accentuate as the target oligosaccharide becomes bigger and more complex. To overcome these challenges, a cellobiose-based metabolism that exploits energy-efficient phosphorolysis will be established to meet the high demand of cellular energy for synthesis. Using cellobiose based metabolism allows glucose, the best energy source, to be used without triggering its repression on the uptake of other sugars, thus enabling engineered biocatalysts to access multiple sugars as they are needed. The complexity of the biochemical network necessary for oligosaccharide synthesis is further addressed by breaking a complex reaction network into several small modules that are designed to be sequentially executed. Each module is activated at a time and for a duration dictated by a target oligosaccharide. This approach allows microbial biocatalysts to devote cellular resources (ATP, glycosyltransferase enzymes, and precursor pools) to only one glycosidic bond formation at a time so that it performs each glycosylation step efficiently. The methods used will include the expression of specific enzymes involved in oligosaccharide synthesis and the application of optimized feeding and bioprocessing strategies during synthesis of the desired compounds.
This award by the Biotechnology and Biochemical Engineering Program of the CBET Division is co-funded by the Systems and Synthetic Biology Program of the Division of Molecular and Cellular Biology.
