An Aspergillus nidulans endo-β-1,3-glucanase exhibited specific catalytic features and was used to prepare 3-O-β-cellobiosyl-d-glucose and 3-O-β-gentiobiosyl-d-glucose with high antioxidant activity from barley β-glucan and laminarin, respectively

An endo -β-1,3(4)-glucanase AnENG16A from Aspergillus nidulans shows distinctive catalytic features for hydrolysis of β-glucans. AnENG16A hydrolyzed Eisenia bicyclis laminarin to mainly generate 3-O-β-gentiobiosyl- d -glucose and hydrolyzed barley β-glucan to mainly produce 3-O-β-cellobiosyl- d -glucose. Using molecular exclusion chromatography, we isolated and purified 3-O-β-cellobiosyl- d -glucose and 3-O-β-gentiobiosyl- d -glucose, respectively, from AnENG16A-hydrolysate of barley β-glucan and E. bicyclis laminarin. Further study reveals that 3-O-β-cellobiosyl- d -glucose had 8.99-fold higher antioxidant activity than barley β-glucan and 3-O-β-gentiobiosyl- d -glucose exhibited 43.0% higher antioxidant activity than E. bicyclis laminarin. Notably, 3-O-β-cellobiosyl- d -glucose and 3-O-β-gentiobiosyl- d -glucose exhibited 148.9% and 116.0% higher antioxidant activity than laminaritriose, respectively, indicating that β-1,4-linkage or -1,6-linkage at non-reducing end of β-glucotrioses had enhancing effect on antioxidant activity compared to β-1,3-linkage. Furthermore, 3-O-β-cellobiosyl- d -glucose showed 237.9% higher antioxidant activity than cellotriose, and laminarin showed 5.06-fold higher antioxidant activity than barley β-glucan, indicating that β-1,4-linkage at reducing end of β-glucans or oligosaccharides resulted in decrease of antioxidant activity compared to β-1,3-linkage. • A distinctive β-glucanase for preparation of glucooligosaccharide from β-glucan • Superdex™ 30 open column can efficiently purification of glucooligosaccharides. • Antioxidant activity increases with increase of DP of glucooligosaccharides. • β-1,4/1,6-Linkage at non-reducing end enhance antioxidant activity of oligosaccharide. • β-1,4-Linkage at reducing end decreases antioxidant activity of glucooligosaccharide. [ABSTRACT FROM AUTHOR]