Short communication: Gelatinization and enzymatic hydrolysis characteristics relevant to digestion and analysis of glycogen granules isolated from ruminal protozoa

摘要

Glycogen is an α-glucan produced by rumen microbesfrom various feed carbohydrates. It may bedigested ruminally or intestinally to provide nutrients.The physicochemical and enzymatic hydrolysis characteristicsof microbial glycogen have not been describedin detail, but do influence its conversion to absorbablenutrients in vivo, its nutritional comparability withplant starch sources, and its accurate analysis in vitro.The objectives of this study were to determine presenceor absence of a gelatinization response and todescribe enzymatic digestion characteristics of glycogengranules isolated from ruminal protozoa obtained fromlactating dairy cows. Protozoal glycogen granules weredetermined to be 98.3% α-glucan. Granules displayedgelatinization, the breaking of hydrogen bonds betweenmolecules or branches, at 65°C compared with purifiedwheat and corn starches, which initiated gelatinizationat 50 and 65°C, respectively. Digestion of ungelatinizedsamples with amyloglucosidase for 2 h at 39°C showedapproximately 3-fold greater hydrolysis to glucose forprotozoal glycogen (25.2% of dry matter; DM) than forwheat (9.9% of DM) or corn (8.2% of DM) starches.Based on enzymatic digestion results, protozoal glycogenmay be more readily digested than intact corn orwheat starches and should be gelatinized or the hydrogenbonds otherwise disrupted to allow more completerecovery in enzymatic analysis.