Food Engineering Department, Ordu University, Ordu, 52200, Turkey.
Whistler Center for Carbohydrate Research, Department of Food Science, Purdue University, West Lafayette, IN, 47907, USA.
Sci Rep. 2018 Nov 9;8(1):16655. doi: 10.1038/s41598-018-34912-8.
Though the physical structuring of insoluble dietary fiber sources may strongly impact their processing by microbiota in the colon, relatively little mechanistic information exists to explain how these aspects affect microbial fiber fermentation. Here, we hypothesized that wheat bran fractions varying in size would be fermented differently by gut microbiota, which would lead to size-dependent differences in metabolic fate (as short-chain fatty acids; SCFAs) and community structure. To test this hypothesis, we performed an in vitro fermentation assay in which wheat bran particles from a single source were separated by sieving into five size fractions and inoculated with fecal microbiota from three healthy donors. SCFA production, measured by gas chromatography, uncovered size fraction-dependent relationships between total SCFAs produced as well as the molar ratios of acetate, propionate, and butyrate. 16S rRNA sequencing revealed that these size-dependent metabolic outcomes were accompanied by the development of divergent microbial community structures. We further linked these distinct results to subtle, size-dependent differences in chemical composition. These results suggest that physical context can drive differences in microbiota composition and function, that fiber-microbiota interaction studies should consider size as a variable, and that manipulating the size of insoluble fiber-containing particles might be used to control gut microbiome composition and metabolic output.
尽管不溶性膳食纤维来源的物理结构可能会强烈影响其在结肠中被微生物群的加工，但目前几乎没有机制信息可以解释这些方面如何影响微生物纤维发酵。在这里，我们假设大小不同的麦麸会被肠道微生物群以不同的方式发酵，这将导致代谢命运（如短链脂肪酸；SCFAs）和群落结构的尺寸依赖性差异。为了验证这一假设，我们进行了一项体外发酵试验，其中从单一来源分离的麦麸颗粒通过筛分分为五个大小级分，并接种来自三个健康供体的粪便微生物群。通过气相色谱法测量的 SCFA 产量揭示了总 SCFA 产生以及乙酸盐、丙酸盐和丁酸盐的摩尔比之间与大小有关的关系。16S rRNA 测序表明，这些依赖于大小的代谢结果伴随着微生物群落结构的不同发展。我们进一步将这些不同的结果与化学组成中细微的、依赖于大小的差异联系起来。这些结果表明，物理环境可以驱动微生物群落组成和功能的差异，纤维-微生物群相互作用研究应将大小视为一个变量，并且操纵含有不溶性纤维的颗粒的大小可能用于控制肠道微生物组组成和代谢产物。
