Hyaluronan production and molecular weight is enhanced in pathway-engineered strains of lactate dehydrogenase-deficient .

The potential advantages of hyaluronic acid (HA) production by metabolically-engineered is constrained by the lower molecular weight and yield of HA obtained in these strains, compared to natural producers. Earlier studies have correlated lower HA yield with excessive lactate production in . cultures (Chauhan et al., 2014). In the present study, a three-fold increase was observed in the amount as well as molecular weight of HA produced by recombinant -mutant . strains. The diversion from lactate production in the -mutant strains resulted in excess ethanol and acetoin production and higher NAD/NADH ratio in these cultures. The initial NAD/NADH ratio showed a positive correlation with HA molecular weight as well as with the HA-precursor ratio (UDP-GlcUA/UDP-GlcNAc). The influence of NAD/NADH ratio on regulation of the concerned metabolic pathways was assessed by transcriptional analysis of key genes having putative binding sites of the NADH-binding transcriptional factor, Rex.