Prebiotic Potential of Non-digestible Oligosaccharides Isolated from Barnyard Millet ( Echinochloa frumentacea ) Grain

ABSTRACT It is encouraging to see the growing acceptance of millet among the general public, driven by its numerous health benefits. Various research efforts have focused on the many non-digestible oligosaccharides (NDOs) in millets, given their significant nutraceutical potential. Barnyard millet is a viable candidate for extracting NDOs owing to its superior nutritional value and affordability. In the present study, crude oligosaccharides were extracted from barnyard millet under optimized conditions: 80% aqueous ethanol (v/v) at a 1:5 sample-to-solvent ratio for 1 h at 60 °C, yielding 3.61±0.24%. Extracted oligosaccharides were further purified through adsorption chromatography and dialyzed through dialysis membranes (500 Da). Several significant peaks at m/z values of 527, 689, 852, 1014, and 1338 were detected in the MALDI-TOF mass spectrum, indicating that barnyard millet oligosaccharides (BMOs) comprise various oligosaccharides with degrees of polymerization (DP) from 3 to 8. BMOs were treated with digestive enzymes (porcine pancreatic and salivary α-amylase) and an artificial acidic solution, and results showed that approximately 91% of BMOs were not digested. The positive prebiotic scores and the generation of lactic and short-chain fatty acids (SCFAs) upon fermentation by various probiotic strains indicate the prebiotic potential of BMOs. In this study, the results also showed that the presence of BMOs increased auto-aggregation of lactobacilli and enhanced the adhesion of probiotics to HCT116 cells. Our findings indicate that, with its nutritional benefits, barnyard millet may serve as a viable reservoir of beneficial carbohydrates, including NDOs. Highlights Extraction of BMOs under optimized parameters. Partial purification of BMOs through charcoal column chromatography and dialysis. A positive prebiotic activity score conferred the prebiotic potential of BMOs. Production of short-chain fatty acids by fermentation of BMOs. BMOs increased the auto-aggregation percentage of different probiotics. Competing Interest Statement The authors have declared no competing interest. Abbreviation - v/v - volume/volume - FOS - Fructooligosaccharides - XOS - Xylooligosaccharides - GI - Gastrointestinal - MWCO - Molecular Weight Cut-Off - w/v - weight/volume - MALDI-TOF - Matrix-Assisted Laser Desorption Ionization—Time of Flight - MRS - De Man-Rogosa-Sharpe - HPLC - High-Performance Liquid Chromatography - DAD - Diode Array Detector - DMEM - Dulbecco’s Modified Eagle Medium