(582bp) Metabolic Engineering of Escherichia Coli for the Production of Medically Valuable Polysaccharides

Although microbial capsules have traditionally been studied due to the protective effects they confer to their bearers during infection in the face of host immune systems, a specific subset of capsular polysaccharides can serve as precursors to the production of medically important glycosaminoglycans such as heparin and chondroitin sulfate. Our lab has recently sequenced the genomes of two heparosan-producing Escherichia coli strains, Nissle 1917 and K5, and  a chondroitin producing E. coli strain, K4. Genome-scale models have been constructed and used for prediction of genetic interventions—gene deletions, knockdowns, and overexpressions—leading to increased capsular polysaccharide production. Comparative genomics analyses between these capsule producing strains and model acapsular strains are ongoing to understand differences in nucleotide sugar metabolism and carbon utilization that might have evolved between these classes of microbes. Additionally, DNA aptamers have been selected against purified capsular polysaccharides for use in high-throughput screens. Our work covers a broad range of complementary engineering and informatics approaches and demonstrates the feasibility of producing commercially relevant levels of heparin and chondroitin sulfate from bacterial sources.