In vitro and in vivo digestibility of prebiotic galactooligosacharides synthesized by β ‐galactosidase from Lactobacillus delbruecki subsp. bulgaricus CRL450

Abstract

BACKGROUND: To date, the general belief that prebiotics reach the colon without any alterations is challenged. Some in vitro and in vivo studies have demonstrated that "non-digestible" oligosaccharides are digested to different degrees depending on their structural composition. In this work, we compared different methods to assess the digestibility of oligosaccharides synthesized by β-galactosidase (β-gal) of Lactobacillus delbruecki subsp. bulgaricus CRL450 (CRL450-β-gal) from lactose, lactulose and lactitol. RESULTS: In simulated gastrointestinal fluid (SGIF) method no changes were observed. However, the oligosaccharides synthesized by CRL450-β-gal were partially hydrolyzed in vitro, depending on their structure and composition, with rat small intestinal extract (RSIE) and small intestinal brush-border membrane vesicles (BBMV) from pig. Digestion of some oligosaccharides increased when mixtures were fed to C57BL/6 mice used as in vivo model, however, lactulose-oligosaccharides were the most resistant to the physiological conditions of mice. In general β(1→6) linked products showed higher resistance compared to β(1→3) oligosaccharides. CONCLUSION: In vitro digestion methods, without disaccharidases, may underestimate the importance of carbohydrates hydrolysis in the small intestine. Although BVMM and RSIE digestion assays are appropriate in vitro methods for these studies, in vivo studies remain the most reliable for understanding what actually happens in the digestion of oligosaccharides.