Process for the preparation of hyaluronic acid in Bacillus megaterium, comprising the following steps: (a) culture of bacterial host cells of Bacillus megaterium transformed in a stable way with the T7 RNA polymerase system under conditions suitable for the production of hyaluronic acid in the presence of xylose as inductor, wherein said bacterial host cells are characterised by being further transformed with: (i) at least one episomal plasmid vector comprising a sequence coding for the enzyme hyaluronan synthase and a sequence coding for the enzyme UDP-glucose dehydrogenase in tandem under the control of the strong inducible T7 promoter, preferably under the control of the strong inducible T7 promoter of bacteriophage T7; or (ii) at least one episomal plasmid vector comprising a sequence coding for the enzyme hyaluronate synthase, a sequence coding for the enzyme UDP-glucose dehydrogenase, a sequence coding for the enzyme UDP-glucose pyrophosphorylase and a sequence coding for the enzyme glucose 6 phosphate isomerase, under the control of the strong inducible T7 promoter, preferably under the control of the strong inducible T7 promoter of bacteriophage T7; (b) recovery of hyaluronic acid from the culture medium, wherein such bacterial host cells of Bacillus megaterium transformed in a stable way with the T7 RNA polymerase system and with plasmid vector (i) or (ii) able to produce hyaluronic acid of step a) are pre-selected in the plate on a xylose gradient. (a) culture of bacterial host cells of Bacillus megaterium transformed in a stable way with the T7 RNA polymerase system under conditions suitable for the production of hyaluronic acid in the presence of xylose as inductor, wherein said bacterial host cells are characterised by being further transformed with: (i) at least one episomal plasmid vector comprising a sequence coding for the enzyme hyaluronan synthase and a sequence coding for the enzyme UDP-glucose dehydrogenase in tandem under the control of the strong inducible T7 promoter, preferably under the control of the strong inducible T7 promoter of bacteriophage T7; or (ii) at least one episomal plasmid vector comprising a sequence coding for the enzyme hyaluronate synthase, a sequence coding for the enzyme UDP-glucose dehydrogenase, a sequence coding for the enzyme UDP-glucose pyrophosphorylase and a sequence coding for the enzyme glucose 6 phosphate isomerase, under the control of the strong inducible T7 promoter, preferably under the control of the strong inducible T7 promoter of bacteriophage T7; (i) at least one episomal plasmid vector comprising a sequence coding for the enzyme hyaluronan synthase and a sequence coding for the enzyme UDP-glucose dehydrogenase in tandem under the control of the strong inducible T7 promoter, preferably under the control of the strong inducible T7 promoter of bacteriophage T7; or (ii) at least one episomal plasmid vector comprising a sequence coding for the enzyme hyaluronate synthase, a sequence coding for the enzyme UDP-glucose dehydrogenase, a sequence coding for the enzyme UDP-glucose pyrophosphorylase and a sequence coding for the enzyme glucose 6 phosphate isomerase, under the control of the strong inducible T7 promoter, preferably under the control of the strong inducible T7 promoter of bacteriophage T7; (b) recovery of hyaluronic acid from the culture medium,