Microbial Cells Possessing a Reduced Lactose Internalization For Producing an Oligosaccharide
Disclosed are genetically engineered microbial cells for the production of an oligosaccharide of interest, wherein said microbial cells possess a variant of the E. coli lactose permease LacY which exhibits a reduced transport activity for lactose, and methods for producing an oligosaccharide by using said genetically engineered microbial cells.
1 . A genetically engineered microbial cell for the production of an oligosaccharide of interest, wherein said microbial cell comprises a lactose permease for internalizing exogenous lactose, wherein said lactose permease is a variant of the E. coli lactose permease LacY which exhibits a reduced internalization of lactose as compared to E. coli wild-type LacY.
2 . The genetically engineered microbial cell according to claim 1 , wherein the variant of the E. coli lactose permease LacY has a sequence identity of at least 70%, at least 80%, at least 90%, at least 95% sequence identity to E. coli wild-type lactose permease LacY.
3 . The genetically engineered microbial cell according to claim 1 or 2 , wherein the variant of the E. coli lactose permease LacY comprises a basic amino acid residue in at least one of amino acid positions 292, 293 and 293 with respect to the lactose permease as represented by SEQ ID No. 1.
4 . The genetically engineered microbial cell according to claim 3 , wherein the basic amino acid residue is selected from the group consisting of arginine, histidine and lysine.
5 . The genetically-engineered microbial cell according to any one of claims 1 to 4 , wherein the microbial cell comprises a nucleic acid molecule comprising a nucleotide sequence from the group consisting of
a) nucleotide sequences encoding a variant of the E. coli wild-type lactose permease LacY as defined in any one of claims 1 to 4 ,
b) nucleotide sequences which are complementary to any one of the nucleotide sequences of a);
c) nucleotide sequences that hybridize to any one of the nucleotide sequences set forth in a) or b) under stringent conditions.
6 . The genetically engineered microbial cell according to claim 5 , wherein the nucleotide sequence encoding a variant of the E. coli wild-type lactose permease LacY is operably inked to expression control sequences.
7 . The genetically engineered microbial cell according to any one of claims 1 to 6 , wherein the microbial cell further comprises
at least one metabolic pathway for intracellular biosynthesis of a nucleotide activated sugar; and
at least one glycosyltransferase for transferring intracellularly a monosaccharide moiety from the nucleotide-activated monosaccharide as donor substrate to lactose or an oligosaccharide as acceptor molecule.
8 . Use of a genetically engineered microbial cell according to any one of claims 1 to 7 for the production of an oligosaccharide of interest, wherein said oligosaccharide of interest comprises a lactose moiety at its reducing end.
9 . A method for producing an oligosaccharide of interest, wherein the oligosaccharide of interest is synthesized in a microbial cell, the method comprises:
providing a genetically engineered microbial cell for intracellular biosynthesis of the oligosaccharide as defined in any one of claims 1 to 7 ;
cultivating the genetically engineered cell in the presence of exogenous lactose in a medium and under conditions allowing the cell to intracellularly synthesize the oligosaccharide of interest; and
recovering the oligosaccharide of interest from the culture medium or the cell.
10 . The method according to claim 9 , wherein the oligosaccharide is selected from the group consisting of 2′-fucosyllactose (2′-FL), 3-fucosyllactose (3-FL), 2′,3-difucosyllactose (DFL), lacto-N-triose II, lacto-N-tetraose (LNT), lacto-N-neotetraose (LNnT), lacto-N-fucopentaose I (LNFP-I), lacto-N-neofucopentaose I (LNnFP-I), lacto-N-fucopentaose II (LNFP-II), lacto-N-fucopentaose III (LNFP-III), lacto-N-fucopentaose V (LNFP-V), lacto-N-neofucopentaose V (LNnFP-V), lacto-N-hexaose (LNH), lacto-N-neohexaose (LNnH), para-lacto-N-hexaose (paraLNH), para-lacto-N-neohexaose (paraLNnH), difucosyl-lacto-N-neohexaose (DF-LNnH), lacto-N-difucosylhexaose I, lacto-N-difucosylhexaose II, para-lacto-N-fucosylhexaose (paraLNH), fucosyl-lacto-N-sialylpentaose a (F-LST-a), fucosyl-lacto-N-sialylpentaose b (F-LST-b), fucosyl-lacto-N-sialylpentaose c (F-LST-c), fucosyl-lacto-N-sialylpentaose c, disialyl-lacto-N-fucopentaose, 3-fucosyl-3′-sialyllactose (3F-3′-SL), 3-fucosyl-6′-sialyllactose (3F-6′-SL), lacto-N-neodifucohexaose I, 3′-sialyllactose (3-SL), 6′-sialyllactose (6-SL), sialyllacto-N-tetraose a (LST-a), sialyllacto-N-tetraose b (LST-b), sialyllacto-N-tetraose c (LST-c), disialyllacto-N-tetraose (DS-LNT), Disialyl-lacto-N-fucopentaose (DS-LNFP V), lacto-N-neodifucohxaose I (LNnDFH I), 3′-galactosyllactose (3′-GL), 6′-galactosyllactose (6′-GL).