In Vitro Digestibility of Galactooligosaccharides: Effect of the Structural Features on Their Intestinal Degradation

Abstract

Small intestinal brush border membrane vesicles (BBMV) from pig were used to evaluate the digestibility of different mixtures of galactooligosaccharides from lactose (GOS), differing in the predominant glycosidic linkage, and from lactulose (OsLu). Dissimilar hydrolysis rates were detected after BBMV digestion. Predominant glycosidic linkages and monomeric composition showed to play a key role in the resistance to intestinal mammalian digestive enzymes. β(1→3) GOS mixture was the most susceptible to hydrolysis with 50.2 % of degradation after digestion, followed by β(1→4) with 34.9 % hydrolysis, whereas β(1→6) linkages showed to be highly resistant to digestion (27.1 %). Monomeric composition seems to provide a better resistance in β(1→6) oligosaccharides from lactulose (22.8 %) as compared to β(1→6)-GOS (27.1 %). This was also observed in β-galactosyl-fructoses and β-galactosyl-glucoses disaccharides where the presence of fructose provided a higher resistance to digestion. Thus, the resistance to small intestinal digestive enzymes highly depends on structural characteristic and composition of prebiotic ingredients. Increasing knowledge on this regard could contribute to the future synthesis of new tailored prebiotic with specific functional properties.

Evaluation of the impact of a rat small intestinal extract on the digestion of four different functional fibers

“…These results underline the relevance of the higher M w composition in terms of digestibility. 16,36 Higher hydrolysis in Inulin Orafti GR was observed in the tetrasaccharide fraction after 180 min of digestion, supporting the data obtained in the in vivo and in vitro studies by Ferreira-Lazarte et al (2017) 14 and Molis et al (1996), 37 resulting in 12% and 11% of total digestion, respectively. In the case of Raftilose P95, a not significant decrease of tri-and tetrasaccharides was observed: hydrolysis being higher in the case of the linkage β(2 → 1) between fructose monomers (inulotriose and inulotetraose of Raftilose P95), when glucose is not present in the structure ending compared to sucrose oligosaccharides (kestose and nystose of Inulin Orafti GR) ( Table 2).…”

“…20,21,46 These enzymatic structures could also have more versatility in terms of hydrolytic activity, as was showed elsewhere. 16,47 To the best of our knowledge, these data are the first evidence about digestibility of α-GOS with small intestine enzymes.…”

“…42 Considering the sum of total oligosaccharides of AlphaGOS P (manninotriose and verbascotetraose) the hydrolysis was considerably high (61.2%) ( Table 2), despite the lack of pancreatic α-galactosidase in mammals. 43 However, Ferreira-Lazarte et al (2019) 16 showed meaningful hydrolysis degree of prebiotic β-GOS (53% for linkages β(1 → 3)) using brush border membrane vesicles of small intestine of pig. A possible explanation for this fact could be the promiscuous multienzymatic complexes in the rat small intestine extract.…”

“…Increases in galactose levels also suggest that linkages between galactose monomers are being broken by digestive enzymes, similar to the degradation of β-GOS derived from lactose and lactulose observed during small intestinal digestion in previous works. 14,16,36,38,39 Beneficial effect of the α-GOS on the modulation of the intestinal microbiota is wellknown. 40,41 Nevertheless, there is not enough information about their digestibility, even the expert scientific panel from the European Food Safety Authority (EFSA) claims that the α-GOS are non-digestible carbohydrates.…”

“…12,13 Recently, a promising in vitro digestibility method of dietary carbohydrates using rat small intestinal extract (RSIE) has questioned the belief that recognized prebiotics oligosaccharides derived from lactose (GOS) and fructooligosaccharides (FOS) reach the distal portions of colon without alterations. [14][15][16] Therefore, with the aim of gain more insight on the benefits of non-digestible carbohydrates, in this work the digestibility of commercial functional fiber, such as α-galactooligosaccharides derived from peas and different types of fructans have been tested using a rat small intestine extract.…”