Production of galactooligosaccharides and heterooligosaccharides with disrupted cell extracts and whole cells of lactic acid bacteria and bifidobacteria

This study employed β-galactosidases present in disrupted crude cell extracts (CCEs) and whole cells of lactic acid bacteria (LAB) and bifidobacteria for formation of galactooligosaccharides (GOSs) and heterooligosaccharides (HeOSs) from lactose and the acceptor carbohydrates mannose, fucose, N-acetylglucosamine (GlcNAc) and sialic acid. CCEs and whole cells successfully produced up to three HeOSs with mannose, fucose or GlcNAc in addition to GOS, but did not utilize sialic acid as acceptor. Synthesis of HeOS by a heterologously expressed β-galactosidase of Streptococcus thermophilus verified that HeOSs were indeed formed by β-galactosidases present in CCEs or whole cells. Heterologously expressed β-galactosidases of S. thermophilus and Lactobacillus plantarum hydrolysed the novel HeOSs and confirmed, for the first time, fucose as an acceptor carbohydrate. In summary, LAB CCEs and bifidobacteria CCEs and whole cells are suitable sources of β-galactosidases that can be used to synthesize novel HeOSs with potentially expanded functionality in addition to GOSs.