Polysaccharide

Organic chemistry

Hydrolysis

Fermentation

Fraction (chemistry)

Chemistry

Periodate

Glucan

Pentose

Residue (chemistry)

Chromatography

Journal of the Institute of Brewing

A nitrogen-free non-starchy polysaccharide was isolated from frozen beer precipitate by repeated precipitation with ethanol, and further fractionated with ammonium sulphate into a pentose-free fraction (G-1) and a pentose-containing fraction (G-2). The G-1 fraction, which constituted about 90% of the non-starchy polysaccharide, was composed solely of glucose residues united by β-linkages, as evidenced by the specific rotation (-12°) and the infrared absorption spectrum. The G-1 glucan gave glucose, celloblose, and laminaribiose on partial acid hydrolysis. Hydrolysis of the methylated G-1 glucan gave 2,3,6-tri-O-methyl-D-glucose and 2,4,6-tri-O-methyl-D-glucose together with trace amounts of 2,3,4,6-tetra-O-methyl-D-glucose and di-O-methyl-D-glucose (paper chromatography). Gas chromatography of the methanolysate of the methylated G-1 glucan indicated the presence of methyl 2,3,6-tri-O-methyl-D-glucopyranoside and methyl 2,4,6-tri-O-methyl-D-glucopyranoside with a proportion of 3:1. The G-1 glucan consumed 0·8 mole periodate per anhydroglucose residue on periodate oxidation. These results indicate that the G-1 glucan is a β-glucan of essentially linear structure containing β-1,4- and β-1,3-linked glucopyranose residues in proportions of 3:1 to 4:1. The molecular weight of the G-1 glucan was estimated as 114,000.

STUDIES ON FROZEN BEER PRECIPITATES II. CHEMICAL STRUCTURE OF THE β-GLUCAN ISOLATED FROM THE PRECIPITATES