Enzyme-Synthesized Highly Branched Maltodextrins Have Slow Glucose Generation at the Mucosal α-Glucosidase Level and Are Slowly Digestible In Vivo

Abstract

For digestion of starch in humans, α-amylase first hydrolyzes starch molecules to produce α-limit dextrins, followed by complete hydrolysis to glucose by the mucosal α-glucosidases in the small intestine. It is known that α-1,6 linkages in starch are hydrolyzed at a lower rate than are α-1,4 linkages. Here, to create designed slowly digestible carbohydrates, the structure of waxy corn starch (WCS) was modified using a known branching enzyme alone (BE) and an in combination with β-amylase (BA) to increase further the α-1,6 branching ratio. The digestibility of the enzymatically synthesized products was investigated using α-amylase and four recombinant mammalian mucosal α-glucosidases. Enzyme-modified products (BE-WCS and BEBA-WCS) had increased percentage of α-1,6 linkages (WCS: 5.3%, BE-WCS: 7.1%, and BEBA-WCS: 12.9%), decreased weight-average molecular weight (WCS: 1.73×108 Da, BE-WCS: 2.76×105 Da, and BEBA-WCS 1.62×105 Da), and changes in linear chain distributions (WCS: 21.6, BE-WCS: 16.9, BEBA-WCS: 12.2 DPw). Hydrolysis by human pancreatic α-amylase resulted in an increase in the amount of branched α-limit dextrin from 26.8% (WCS) to 56.8% (BEBA-WCS). The α-amylolyzed samples were hydrolyzed by the individual α-glucosidases (100 U) and glucogenesis decreased with all as the branching ratio increased. This is the first report showing that hydrolysis rate of the mammalian mucosal α-glucosidases is limited by the amount of branched α-limit dextrin. When enzyme-treated materials were gavaged to rats, the level of postprandial blood glucose at 60 min from BEBA-WCS was significantly higher than for WCS or BE-WCS. Thus, highly branched glucan structures modified by BE and BA had a comparably slow digesting property both in vitro and in vivo. Such highly branched α-glucans show promise as a food ingredient to control postprandial glucose levels and to attain extended glucose release.

A Survey of Commercially Available Isomaltooligosaccharide‐Based Food Ingredients

“…A review of the literature differentiated the digestibility of RMDx from resistant starch, a high molecular weight polyglucan that is either retrograded, granular (and hence resistant to amylolytic activity), or chemically modified so as to be indigestible (Sajilata and others ; Fuentes‐Zaragoza and others ). RMDx can be subdivided as (1) an indigestible, highly branched glucan made from starch via heat, acid, and/or α and β‐amylases, (2) other enzymes that transglycosylate starch to yield a variety of linkage types (Lee et al ), or (3) known as “limit dextrins,” are relatively small, glycogen‐like α‐(1,4) glucans that are α‐(1,6) branched so as to resist the further action of α‐amylase (α‐limit dextrin can also be made). α‐D‐1,6‐glucan‐6‐hydrolases (dextranase), pullulan α‐1,6‐glucanhydrolases (pullulanase), and so on, should be able to quickly reduce it into a digestible form, for example, oligo amylose (maltodextrin).…”

Enzymatic modification of corn starch with 4-α-glucanotransferase results in increasing slow digestible and resistant starch

“…Therefore, improving food quality with higher amounts of SDS is becoming an area of interest for researchers from industry and academia, due to fewer amounts of SDS in thermal processing carbohydrate products. Meanwhile, there are limit reports on SDS preparation by using enzymatic method [2,6].…”

Biochemical Characterization of the Lactobacillus reuteri Glycoside Hydrolase Family 70 GTFB Type of 4,6-α-Glucanotransferase Enzymes That Synthesize Soluble Dietary Starch Fibers

“…Of all the nutritional types of starch, slowly digestible starch with low GI has drawn the strongest interest. Annealing/heatmoisture treatment, recrystallization, and enzymatic treatment are recognized approaches to obtain slowly digestible starch (9)(10)(11). Slowly digestible starch materials prepared by physical processing suffer losses upon boiling; therefore, structural modifications through enzymatic treatment of starch are more desirable.…”