Abstract
Arabinogalactan (AG) is a kind of water-soluble polysaccharide, which is long, densely branched and consists of galactose and arabinose. Type II AG composed of β-(1→3)-linked galactan main chain with frequent arabinose and galactose residues containing side chains. Furthermore, Type II AG is frequently distributed in coffee beans. AG from coffee beans was investigated for its effect on the growth of established enterobacterial strains. Thirty-four species of enterobacteria were cultivated in AG-containing media. After 72 hours cultivation, the cell number of Bifidobacterium longum and Bifidobacterium pseudocatenulatum especially increased, pH of the media significantly decreased and both DL-lactic acid and acetic acid accumulated. The enzyme produced by B. longum in the supernatant of its culture showed hydrolyzing activity toward AG from coffee bean and AG from larch wood. This enzyme generated arabinose, galactose, and unknown oligosaccharide when it was incubated with AGs. These observations indicate that B. longum and B. pseudocatenulatum selectively utilize AG as carbon-source. The digestion of AG by artificial digestive juices was investigated in vitro. AG artificial pancreatic juice, and only slightly digested by small intestinal enzymes. Therefore it could be expected that AG from coffee beans had potential as a prebiotic to promote the improvement of healthful human intestinal microflora.
