Certain bacterial pathogens, namely Gram-negative Pasteurella multocida or Escherichia coli and Gram-positive Groups A and C Streptococci, produce extracellular capsules composed of glycosaminoglycans [GAGs] including hyaluronan (hyaluronic acid, HA), chondroitin, and heparosan.  These linear polysaccharides also form the backbones of polymers in many vertebrate tissues.
     Several current therapies and surgeries employ GAGs resulting in a growing ~$2-6 billion/year market. Currently, heparin and chondroitin sulfate are only produced from animal products (porcine intestinal mucosa and bovine or shark cartilage, respectively) and are neither very chemically defined nor safe from contamination with adventitious agents or allergens.  In addition, endangered species like sharks are rapidly disappearing.  Previously, extraction of rooster comb or fastidious Streptococcus was utilized to prepare HA commercially.  Now, new renewable systems for producing GAGs have been developed by harnessing the bacterial systems via fermentation in vivo or via chemoenzymatic synthesis in vitro.
     GAG synthase genes have been transferred into Bacillus subtilis, a safe industrial ‘workhorse’ microbe with high productivity in defined minimal media.  Metabolic engineering of the UDP-sugar precursor pools boosted GAG yields substantially.  Recombinant HA polysaccharide was recently launched on the commercial market.
     We have developed methods to construct large GAG polysaccharides of a desired size by controlling stoichiometry in synchronized reactions.  We have also created GAG oligosaccharide synthesis systems employing immobilized mutant enzyme reactors in a step-wise sugar addition strategy.  Defined GAG molecules should be of great use in emerging therapies including the treatment of wounds and cancer in the near future.