Impact of degree of acetylation on the colonic fermentation of plant xylan

Acetyl substitutions play an important role in regulating the physiological functions of xylan. The degree of acetylation, defined by the mole ratio of O-acetyl units to xylosyl units, determines the hydrophobicity of xylan molecules. Acetylation not only influences the physical and chemical properties of xylan but also limits the activity of xylan-degrading enzymes. Considering that plant xylan is a source of dietary fiber, present in grains and vegetables, it is important to understand how it is degraded in the human colon. Few studies connect xylan degree of acetylation with colonic fermentability and the corresponding changes in the human gut microbial community. Therefore, in this study, we aimed to investigate how varying degrees of acetylation influence xylan degradation in the colonic environment, shift the abundance of gut microbial populations, and alter metabolic outcomes. Beechwood xylan (BWX) was chemically modified to reach 0.0, 0.5, 1.1, 1.6, and 1.9 degrees of acetylation, which were denoted BWXDA0.0, BWXDA0.5, BWXDA1.1, BWXDA1.6, and BWXDA1.9, respectively. These five samples were subjected to an in vitro fermentation trial after inoculation with human fecal microbiota.