We examined the in vitro digestibility of maltobionic acid, obtained from enzymatic oxidation of maltose, its utilization by intestinal bacteria, and its biological effects on the bowel movements in healthy subjects. We found that maltobionic acid is not digested in vitro by saliva, gastric juice, or pancreatic juice. Moreover, it is digested only to a small extent by small intestinal enzymes. Among the 24 strains of intestinal bacteria, maltobionic acid was selectively utilized by

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... zed by Bifidobacterium dentium and Bi. adolescentis. We also evaluated the influence of long-term ingestion of maltobionic acid calcium salt on bowel movements in healthy Japanese women by a randomized, double-blind, placebocontrolled, crossover trial. Thirty-four subjects completed the study, and no adverse events related to the test food were observed. Ten subjects were excluded prior to the efficacy analysis because of conflict with the control criteria; the remaining 24 subjects were analyzed. Intake of test food containing 4 g maltobionic acid for 4 weeks caused a significant increase in the stool frequency, significant improvement in stool form scale and CAS-MT total scores as compared with the placebo group. These results suggest that maltobionic acid is an indigestible carbohydrate and is a promising therapeutic agent for improving the intestinal environment. This is an open-access paper distributed under the terms of the Creative Commons Attribution Non-Commercial (by-nc) License (CC-BY-NC4.0: https://creativecommons.org/licenses/by-nc/4.0/). physical properties when formulated into foods because it has an extremely weak calcium-specific bitterness, a high glass transition temperature (T g ) (anhydrous T g = 145 °C), and a non-crystallizing nature even under high relative humidity conditions. 6) While in addition to its use in mineral supplements and acid coagulant applications, gluconic acid, which is a component of maltobionic acid, has been reported to promote the growth of Bifidobacterium, 7) no report on the digestibility of maltobionic acid and its utilization by intestinal bacteria exists. Therefore, in this study, we carried out a comparative in vitro study of digestibility by intestinal enzymes and assimilation by intestinal bacteria of maltobionic acid and other oligosaccharides; we also evaluated their effects on fecal improvement in healthy human subjects. MATERIAL AND METHODS Sample preparation. The analytical grade reagents viz. maltose monohydrate, maltotriose, maltotetraose, maltopentaose, sodium hydrogen carbonate, catalase, and glucose oxidase required for the synthesis of the sodium salts of maltobionic acid, maltotrionic acid, maltotetraonic acid, and maltopentaonic acid were purchased from FUJIFILM Wako Pure Chemical Corporation (Tokyo, Japan) and/or Amano Enzyme Inc. (Aichi, Japan), unless mentioned otherwise. The sodium salt of maltobionic acid was synthe-