Disclosed are genetically engineered microbial cells for the production of oligosaccharides comprising a galactose-β1,4-glucose moiety at their reducing end, wherein said microbial cells are able to produce said oligosaccharides in the absence of exogenously added lactose, and a method of producing said oligosaccharides using said microbial cells.

Disclosed are genetically engineered microbial cells for the production of oligosaccharides comprising a galactose-β1,4-glucose moiety at their reducing end, wherein said microbial cells are able to produce said oligosaccharides in the absence of exogenously added lactose, and a method of producing said oligosaccharides using said microbial cells.

Disclosed are genetically engineered microbial cells for the production of oligosaccharides comprising a galactose-β1,4-glucose moiety at their reducing end, wherein said microbial cells are able to produce said oligosaccharides in the absence of exogenously added lactose, and a method of producing said oligosaccharides using said microbial cells.

Disclosed are genetically engineered microbial cells for the production of oligosaccharides comprising a galactose-1,4-glucose moiety at their reducing end, wherein said microbial cells are able to produce said oligosaccharides in the absence of exogenously added lactose, and a method of producing said oligosaccharides using said microbial cells.

The present invention relates to a method of providing a gene cluster that determines the rare sugar utilization ability of a strain unable to metabolize a rare sugar. A novel sugar metabolic pathway may be constructed using an expression cassette or a vector containing the same according to the present invention, and a mutant strain transformed with the vector or a mutant strain containing a mutated gene has a novel sugar metabolic pathway constructed therein. In addition, the present invention relates to a method for selecting a variant with increased activity, and a composition for selecting a variant with increased activity may be advantageously used to select a variant with increased activity by detecting the mutation of SEQ ID NO: 11.