The BLLJ_1391 protein from Bifidobacterium longum subsp. longum JCM1217, a cytosolic β-N-acetylglucosaminidase belonging to glycoside hydrolase family (GH) 20, hydrolyzed lacto-N-triose II (LNTri) as well as chitin oligosaccharides. Its reaction was found to follow a substrate-assisted mechanism with anomeric retention, which is common for GH 20 enzymes. Homologous enzymes are found in genomic sequences of B. longum subsp. infantis, Bifidobacterium bifidum, and Bifidobacteium breve, all of which are infant gut-associated species of Bifidobacterium. The distribution resembles that of 1,3-β-galactosyl-N-acetylhexosamine phosphorylase, suggesting that the enzyme plays a role in metabolism of human milk oligosaccharides by hydrolyzing LNTri generated via the cytosolic hydrolysis of lacto-N-tetraose (LNT) by LNT 1,3-β-galactosidase.

抄録全体を表示

Potato starch (PS), L (+)-lysine hydrochloride (Lys) and glucose/fructose stearic acid monoester (GE/FE) were conjugated by autoclaving them by heat-moisture treatment (HMT) and the Maillard reaction to prepare PS-Lys-GE/FE conjugate with a molar ratio of PS (as glucose residues) : Lys : GE/FE=684 : 1.0 : 0.66. PS-Lys-GE/FE exhibited increased thermal stability in terms of significantly higher gelatinization temperature, lower gelatinization enthalpy, lower solubility than those of native and control PSs. It maintained the state of swollen granules without collapse, even if heated at 110°C for 30 min. In addition, gelatinized PS-Lys-GE/FE exhibited resistance to digestibility with α-amylase and easy vaporization of water, similar that of free water. Addition of PS-Lys-GE/FE markedly reduced the peak viscosity and breakdown values of wheat flour batter. Simultaneous modification through HMT and the Maillard reaction resulting in conjugation of PS with GE/FE through Lys could provide a conjugated starch material with unique properties in terms of the elevated gelatinization temperature, reduced solubility, swelling and digestibility, easy water vaporization, high thermal resistance, and reduced viscosity of wheat flour batter.

抄録全体を表示