Optimizing the Molecular Weight of Oat β-Glucan for in Vitro Bile Acid Binding and Fermentation

A previous study showed beta-glucan with low molecular weight (MW, 1.56 x 10(5) g/mol) bound more bile acid and produced greater amounts of short-chain fatty acids (SCFA) than did beta-glucan with high MW (M-n = 6.87 x 10(5) g/mol). In the current study, beta-glucan extracted from oat flour was fractionated into six different MW levels (high MW, 7.09 x 10(5); low level I (L1), 3.48 x 10(5); L2, 2.42 x 10(5); L3, 1.61 x 10(5); L4, 0.87 x 10(5); and L5, 0.46 x 10(5) g/mol) and evaluated to find the optimum MW affecting in vitro bile acid binding and fermentation. The beta-glucan fractions with 2.42 x 10(5)-1.61 x 10(5) g/mol (L2 and L3) bound the greatest amounts of bile acid. After 24 h of fermentation, no differences were found in total SCFA formation among L1, L2, L3, and L4 fractions; however, the high MW and L5 MW fractions produced lower amounts of total SCFA. Thus, the optimum MW of beta-glucan to affect both hypocholesterolemic and antitumorigenic in vitro effects was in the range of 2.42 x 10(5)-1.61 x 10(5) g/mol. This MW range also was the most water-soluble among the MWs evaluated.