Journal
BIOTECHNOLOGY JOURNAL
Volume 10, Issue 8, Pages 1307-1315Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/biot.201400602
Keywords
Chondroitin; Escherichia coli K4; GalU overexpression; Pgm overexpression; UDP-sugar pools
Funding
- Antigeni e adiuvanti per vaccini e immunoterapia [PON01_00117]
- Bio Industrial Processes - BIP - Regione Campania [199 - PO FESR]
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Escherichia coli K4 produces a capsule with a chemical structure that resembles chondroitin, a molecule with established chondro protective properties. The endogenous genes pgm and galU are involved in the biosynthesis of UDP-glucose which is a critical intermediate in carbohydrate metabolism and biochemical precursor of UDP-glucuronic acid. Together with UDP-N-acetylgalactosamine, UDP-glucuronic acid is used as sugar donor for capsule biosynthesis. The aim of the study was to evaluate how a change in the pathways leading to UDP-glucuronic acid biosynthesis affected capsular polysaccharide production. One additional copy of pgm and galU was introduced in E. coli K4 and in the previously described recombinant strain EcK4r3. A microbioreactor was used to analyse strain performance with parallel batch experiments, demonstrating increased polysaccharide concentrations and providing data that are comparable to those obtained in larger fermenters. Further experiments on a glutamine enriched medium showed an additional 45% increase of capsule production, maybe indicating the need to balance both branches leading to polymer biosynthesis in order to maximize yields. In the effort towards the establishment of a feasible bio-chondroitin production process this study provides information on how the availability of sugar precursors impacts polysaccharide biosynthesis in E. coli K4, a complex unexplored aspect of a multifaceted process.
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