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1. 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. |
