Modulation of the Human Gut Microbiota by Corn Arabinoxylans: Insights from In Vitro Batch Culture Fermentation
A 24-hour in vitro fermentation study examined how corn arabinoxylans (a cereal fiber) of different molecular weights affect gut microbiota composition and short-chain fatty acid (SCFA) production. Five arabinoxylan preparations (ranging from 225 kDa to <3 kDa) were compared with inulin as a reference prebiotic. After simulated digestion, fibers were fermented using pooled stool from three healthy adults. Researchers measured microbial shifts via 16S rRNA sequencing and quantified SCFAs such as acetate and butyrate.
Results showed that fiber structure strongly shaped fermentation patterns. High-molecular-weight arabinoxylans (225–175 kDa) produced the most sustained effects, increasing Faecalibacterium to ~46% at 18 hours and driving large rises in acetate (~452 μg/mL) and butyrate (~296 μg/mL, p < 0.001). Medium-weight fibers showed a delayed butyrogenic response, while low-molecular-weight forms produced more gradual, moderate SCFA increases. In contrast, inulin caused a rapid early acetate spike (~321 μg/mL at 6 hours) but generated lower and less sustained butyrate overall. Microbial diversity remained stable across treatments.
These findings suggest that more structurally complex, high-molecular-weight fibers promote longer-lasting fermentation and sustained butyrate production, whereas rapidly fermentable fibers drive quicker, shorter-lived effects. The study also shows that small structural differences within the same fiber class can meaningfully redirect microbial and metabolic outcomes.
Limitations include the use of a static in vitro model and pooled donor samples, which cannot fully replicate human physiology. Future research should test these fibers in human trials to determine how molecular weight influences gut and metabolic health in vivo.
Overall, this study reinforces that fiber structure—not just fiber amount—determines functional impact in the gut.
