Aspergillus niger APC-9319株のα-ガラクトシダーゼによるα-結合ガラクトオリゴ糖 (α-GOS) の製造とその諸性質

α-Linked galactooligosaccharide (α-GOS, 7.5 kg) was produced from galactose (18 kg; prepared from lactose hydrolyzate) by the reverse reaction of α-galactosidase from Aspergillus niger APC-9319. α-GOS contained 58% disaccharide, 28% trisaccharide and 14% oligosaccharides larger than trisaccharide The disaccharide in α-GOS consisted largely of α-1,6-galactobiose (73%). α-GOS was stable at neutral and acidic pHs, at temperatures up to 180°C (pH 4.5, 10 min). The water activity of α-GOS was 0.84 (25°C, 70% (w/v)). The powder preparation was highly hygroscopic, and its solution showed higher activity in retaining moisture than sucrose. The sweetness of α-GOS was 25% of that of sucrose. The taste of α-GOS was mild and mellow. α-GOS reduced acid taste, bitterness, astringency, and harsh taste without spoiling the original taste in various fruit juices, and emphasized the original flavor of food materials in various cooked foods. α-GOS was not hydrolyzed in an in vitro digestion method. In an oral α-GOS tolerance test, the blood glucose level did not change at all. α-GOS had a strong selective growth activity for Bifidobacterium sp. and Clostridium butyricum. An α-GOS intake in rats made the content of lactate and n-butyrate in the cecum higher, and pH in the cecum lower than for a control intake. The viable count of Candida albicans in the cecum and colon of mouse was decreased by an α-GOS intake more than by a raffinose intake.