The present disclosure relates to a genetically engineered strain with high production of uridine and its construction method and application. The strain was constructed as follows: heterologously expressing pyrimidine nucleoside operon sequence pyrBCAKDFE (SEQ ID NO:1) on the genome of E coli prompted by strong promoter P.sub.trc to reconstruct the pathway of uridine synthesis; overexpressing the autologous prsA gene coding PRPP synthase by integration of another copy of prsA gene promoted by strong promoter P.sub.trc on the genome; deficiency of uridine kinase, uridine phosphorylase, ribonucleoside hydrolase, homoserine dehydrogenase I and ornithine carbamoyltransferase. When the bacteria was used for producing uridine, 40-67 g/L uridine could be obtained in a 5 L fermentor after fermentation for 40-70 h using the technical scheme provided by the disclosure with the maximum productivity of 0.15-0.25 g uridine/g glucose and 1.5 g/L/h respectively which is the highest level of fermentative producing uridine reported at present.

The present disclosure relates to a genetically engineered strain with high production of uridine and its construction method and application. The strain was constructed as follows: heterologously expressing pyrimidine nucleoside operon sequence pyrBCAKDFE (SEQ ID NO:1) on the genome of E coli prompted by strong promoter P.sub.trc to reconstruct the pathway of uridine synthesis; overexpressing the autologous prsA gene coding PRPP synthase by integration of another copy of prsA gene promoted by strong promoter P.sub.trc on the genome; deficiency of uridine kinase, uridine phosphorylase, ribonucleoside hydrolase, homoserine dehydrogenase I and ornithine carbamoyltransferase. When the bacteria was used for producing uridine, 40-67 g/L uridine could be obtained in a 5 L fermentor after fermentation for 40-70 h using the technical scheme provided by the disclosure with the maximum productivity of 0.15-0.25 g uridine/g glucose and 1.5 g/L/h respectively which is the highest level of fermentative producing uridine reported at present.

The invention provides methods for glycosylation and preparation of compounds. The compounds include galactosylated, sialylated, fucosylated, and N-acetylglucosaminylated compounds from simple animal-derived, plant-derived, or microbe-derived oligosaccharides and sugars. In certain embodiments, the invention provides trinucleotide-free enzymatic production of oligosaccharides starting from simple sugars that include plant-based sugars. The invention also provides the enzymatic production of fucosylated oligosaccharides and fucosylated antibody-glycan conjugates from common sugars. The production may be a cell-free, one-pot synthesis using enzymes, and in some embodiments, immobilized enzymes. The synthesis is a highly customizable and highly efficient cell-free manufacturing process. In some embodiments, lactose derivatives and human milk oligosaccharides (HMOs) are produced.

The invention provides methods for glycosylation and preparation of compounds. The compounds include galactosylated, sialylated, fucosylated, and N-acetylglucosaminylated compounds from simple animal-derived, plant-derived, or microbe-derived oligosaccharides and sugars. In certain embodiments, the invention provides trinucleotide-free enzymatic production of oligosaccharides starting from simple sugars that include plant-based sugars. The invention also provides the enzymatic production of fucosylated oligosaccharides and fucosylated antibody-glycan conjugates from common sugars. The production may be a cell-free, one-pot synthesis using enzymes, and in some embodiments, immobilized enzymes. The synthesis is a highly customizable and highly efficient cell-free manufacturing process. In some embodiments, lactose derivatives and human milk oligosaccharides (HMOs) are produced.

The present invention provides protected tetrasaccharides, their process of preparation and their use in the synthesis of oligosaccharides, in particular fragments of O-antigens from Shigella flexneri, for example of serotype 1a, 1b, 2a, 2b, 3a, X, 4a, 4b, 5a, 5b, 7a or 7b.

The present invention provides protected tetrasaccharides, their process of preparation and their use in the synthesis of oligosaccharides, in particular fragments of O-antigens from Shigella flexneri, for example of serotype 1a, 1b, 2a, 2b, 3a, X, 4a, 4b, 5a, 5b, 7a or 7b.

Disclosed are non-naturally-occurring microorganisms for the production of N-acetylneuraminic acid, a method for the production of N-acetylneuraminic acid by fermentation of the non-naturally-occurring microorganisms, and nutritional compositions containing N-acetylneuraminic acid which has been produced by fermentation of the non-naturally-occurring microorganisms.

Disclosed are non-naturally-occurring microorganisms for the production of N-acetylneuraminic acid, a method for the production of N-acetylneuraminic acid by fermentation of the non-naturally-occurring microorganisms, and nutritional compositions containing N-acetylneuraminic acid which has been produced by fermentation of the non-naturally-occurring microorganisms.

The present invention is directed to microbial production of nicotinamide riboside and/or nicotinamide mononucleotide using a genetically modified fungus.

New 2-deoxy-2,3-dehydro-sialic acids and 2,7-anhydro-sialic acids, which are useful as sialidase inhibitors, and enzymatic methods for preparing them are disclosed. The methods include forming a reaction mixture comprising a glycoside acceptor, a sialic acid donor, and a sialyltransferase; maintaining the reaction mixture under conditions sufficient to form a sialoside; and contacting the sialoside with a Streptococcus pneumoniae sialidase to form the sialic acid product. Methods for the inhibition and sialidases and the treatment of cancer and infectious diseases are also disclosed.