Process for the production of hyaluronic acid in escherichia coli or bacillus subtilis

Process for the production of hyaluronic acid in Escherichia coli or Bacillus subtilis, which comprises:

• (a) culturing bacterial host cells of Escherichia coli that constitutively express the lac repressor, or host cells of Bacillus subtilis transformed with a grac-lac system, under conditions suitable for producing hyaluronic acid, and in the presence of isopropyl-β-thio-galactopyranoside (IPTG) as an inducer, wherein such bacterial host cells are transformed with:
• (i) at least one episomal plasmid vector comprising a sequence coding for hyaluronan synthase, a sequence coding for UDP-glucose dehydrogenase in tandem, under control of a strong inducible promoter Pgrac which uses the lac repressor, or
• (ii) at least one episomal plasmid vector comprising a sequence coding for hyaluronan synthase, a sequence coding for UDP-glucose dehydrogenase, a sequence coding for UDP-glucose pyrophosphorylase and a sequence coding for glucose 6 phosphate isomerase, under control of a strong inducible promoter Pgrac which uses the lac repressor;
• (b) recovering of hyaluronic acid from culture medium;
• wherein said bacterial host cells of Escherichia coli or Bacillus subtilis transformed with plasmid vector (i) or (ii) capable of producing hyaluronic acid of step a) are pre-selected on the IPTG gradient;
• and
• wherein, when bacterial host cells B. subtilis are used, a fermentation time is comprised in the range between 80 and 160 hours to produce HA having a weight average molecular weight comprised in the range 100-500 KD;
• a fermentation time is comprised in the range between 40 and 80 hours to produce HA having a weight average molecular weight comprised in the range 500-1000 KD or a fermentation time is comprised in the range between 12 and 40 hours to produce HA having a weight average molecular weight comprised in the range 1×106-2×106 D.