The present invention provides novel attenuated Pasteurella multocida strains that may be used, in live or killed form, to formulate vaccines that are highly protective against P. multocida infection in bovines, other mammals, and in birds. The present invention also identifies the combination of nanP and hyaC gene mutations as key to the provision of such vaccines. When appropriately formulated, antigenic material of numerous other bovine pathogens may be combined with the live attenuated Pasteurella multocida strains, to make effective combination vaccines.

The present invention relates to a method for the production of hyaluronic acid (HA) in Bacillus subtilis and Escherichia coli through plasmid vectors wherein the gene is under the control of strong promoter Pgrac, and a system for the selection of stable bacterial strains for the production of high levels of hyaluronic acid.

The present invention relates to the field of bio-production of chondroitin. There is a need in the art for chondroitin production methods allowing its highly efficient synthesis and secretion. The solution proposed in the present invention is the use of a recombinant cell, in particular a recombinant yeast, comprising many modifications as described in the present text. The present invention further proposes methods allowing the bio-production of chondroitin using the recombinant cell, in particular a recombinant yeast, of the invention.

The present invention relates to the field of bio-production of heparosan. There is a need in the art for heparosan production methods allowing its highly efficient synthesis and secretion. The solution proposed in the present invention is the use of a genetically modified cell comprising many modifications as described in the present text. The present invention further proposes methods allowing the bio-production of heparosan having a controlled molecular weight using the genetically modified cells of the invention.

The present invention relates to the field of biotechnology engineering. It provides a method of constructing a recombinant Bacillus subtilis that can produce specific-molecular-weight hyaluronic acids. By integranted expression of hasA from Streptococcus zooepidemicus and overexpression of genes of HA synthetic pathway, tuaD, glmU and glmS, high yield HA production was achieved in the recombinant strain. Additionally, introduction and functional expression of the leech hyaluronidase in the recombinant strain substantially increased the yield of HA to 19.38 g.Math.L.sup.1. Moreover, HAs with a broad range of molecular weights (10.sup.3 Da to 10.sup.6 MDa) were efficiently produced by controlling the expression level of hyaluronidase using RBS mutants with different translational strengths. The method of the present invention can be used to produce low molecular weight HAs at large scale in industrial applications.

Testosteronan, a heparosan analog having the structure [-4-D-GlcUA-1,4-D-GlcNAc-1-].sub.n, is produced by testosteronan synthase, a single protein that is a dual-action catalyst that utilizes UDP-GlcUA and UDP-GlcNAc to synthesize a polysaccharide having the structure [-4-D-GlcUA-1,4-D-GlcNAc-1-].sub.n.

A method of producing hyaluronic acid (HA) in Escherichia coli and Bacillus megaterium through episomal plasmid vectors wherein the gene is under the control of strong promoter T7, preferably under the control of strong promoter T7 of bacteriophage T7, and a system for the selection of stable bacterial strains producing high levels of hyaluronic acid, are provided.

Testosteronan, a heparosan analog having the structure [-4-D-GlcUA-1,4-D-GlcNAc-1-].sub.n, is produced by testosteronan synthase, a single protein that is a dual-action catalyst that utilizes UDP-GlcUA and UDP-GlcNAc to synthesize a polysaccharide having the structure [-4-D-GlcUA-1,4-D-GlcNAc-1-].sub.n.

The present invention relates to the field of biotechnology engineering. It provides a method of constructing a recombinant Bacillus subtilis that can produce specific-molecular-weight hyaluronic acids. By integranted expression of hasA from Streptococcus zooepidemicus and overexpression of genes of HA synthetic pathway, tuaD, glmU and glmS, high yield HA production was achieved in the recombinant strain. Additionally, introduction and functional expression of the leech hyaluronidase in the recombinant strain substantially increased the yield of HA to 19.38 g.Math.L.sup.1. Moreover, HAs with a broad range of molecular weights (10.sup.3 Da to 10.sup.6 MDa) were efficiently produced by controlling the expression level of hyaluronidase using RBS mutants with different translational strengths. The method of the present invention can be used to produce low molecular weight HAs at large scale in industrial applications.

The present invention relates to the field of bio-production of hyaluronic acid.

There is a need in the art for hyaluronic acid production methods allowing its highly efficient synthesis and secretion.

The solution proposed in the present invention is the use of a genetically modified cell comprising many modifications as described in the present text.

The present invention further proposes methods allowing the bio-production of hyaluronic acid having a controlled molecular weight using the genetically modified cells of the invention.