In vitro digestion of glycoproteins from Porphyra haitanensis: Effects on structure, hypoglycemic activity, and fermentation characteristics

This study was to investigate the fundamental composition and structure, hypoglycemic activity and fermentation characteristics of Porphyra haitanensis glycoprotein (PG) following in vitro simulate gastrointestinal digestion. After in vitro digestion, PG was degraded into peptides, amino acids, and reducing sugars, and the digested PG structure evolved into functional aggregates that were more favorable for regulating intestinal flora. Such aggregated structure might inhibit the accessibility of digestive enzymes and significantly enhanced its hypoglycemic activity. Compared with undigested PG, the inhibition rate of digested PG on alpha-amylase and alpha-glucosidase was increased by 4.70 % and 7.69 %, respectively (P < 0.05). Furthermore, digested PG enhanced the abundances of Lactobacillus and Bifidobacterium, etc., which was positive related with the increased secretion of butyric acid, thereby playing a role in regulating intestinal homeostasis and blood glucose homeostasis in the host. Our findings can offer novel perspectives on the regulation of the intestinal flora by glycoproteins during gastrointestinal digestion.