Combinations of fermentation and autohydrolysis to produce polysaccharide-based prebiotics from wheat bran and in vitro assessment of their prebiotic potentials

Abstract

Gramineous biomass is an excellent source of polysaccharide-based prebiotics. However, there are shortages of the preparation process due to just xylooligosaccharide (XOS) were exploited, only specific particles from crushed materials were selected and a single concentration of ethanol precipitate were collected. Herein, Bacillus subtilis S1702 fermented wheat bran, 121 °C autohydrolysis with 0.75 M citric acid assistance, 20, 50, 60, and 80% ethanol precipitation were successively adopted to obtained fractions WB20, WB50, WB60, and WB80. It was demonstrated that the combined process including incubation at 37 °C for 36 h by 13% incubation dose, followed by acid-assisted autohydrolysis for 30 min at a solid:liquid ratio of 1:5 (w/v, g/mL), induced the feruloylated arabinoxylan yield of 340.00 ± 0.95 mM, which was significantly higher than those of only autohydrolysis (220.25 ± 1.18 mM) or fermentation and then autohydrolysis without acid assistance (120.76 ± 1.32 mM) (p < 0.05). Furthermore, treatment by WB60 with moderate mass ratio of ferulic acid (FA) to glucan and arabinoxylan being 1:187 showed strong in vitro prebiotic activity based on highest total short-chain fatty acid output, the greatest ratios of butyric acid/acetic acid and Bifidobacteria/Escherichia-Shigella, which was better than those of administration of commercial XOS without FA, WB80 (1:136) and WB50 (1:218) with too higher or lower FA ratio. WB20 with the lowest FA ratio of 1:664 contained different complex polysaccharides and improved gut microbial diversities better than that of XOS. Overall, an appropriate concentration of ethanol precipitate with proper proportion of polyphenols to polysaccharides can improve gut redox imbalance better than purified or simple polysaccharides. This study will lay the foundation for making full use of bran prebiotic by using green technology.