A comprehensive review on the structure-activity relationships and applications of β-D-glucans

β-D-glucan is a polysaccharide formed from glucose monomers linked by beta-glucoside bonds and can be found in grains (barley and oats), yeast and mushrooms. β-D-glucan has a variety of physiological activities, such as immune regulation, anti-tumor, hypoglycemic and regulating gut microbiota, etc. The bioactivity of β-glucan varies with different sources and structures. However, to the best of our knowledge, the structure-activity relationship of β-glucan has not been systematically studied. Based on the most up-to-date published papers, we summarized the source and structure of β-D-glucan, and introduced the various physiological activities of β-D-glucan. More importantly, we discussed the structure-activity relationship of β-D-glucan from various aspects, such as molecular weight, branched chains and structural modification, and summarized the application of β-D-glucan in health product, food and other industries. This review is helpful to systematically understand the structure-activity relationship of β-D-glucan, and further guides its application in food and pharmaceutical industries.