Duncan Sylvia H, Russell Wendy R, Quartieri Andrea, Rossi Maddalena, Parkhill Julian, Walker Alan W, Flint Harry J
Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen, UK.
Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy.
Environ Microbiol. 2016 Jul;18(7):2214-25. doi: 10.1111/1462-2920.13158. Epub 2016 Jan 21.
Cereal fibres such as wheat bran are considered to offer human health benefits via their impact on the intestinal microbiota. We show here by 16S rRNA gene-based community analysis that providing amylase-pretreated wheat bran as the sole added energy source to human intestinal microbial communities in anaerobic fermentors leads to the selective and progressive enrichment of a small number of bacterial species. In particular, OTUs corresponding to uncultured Lachnospiraceae (Firmicutes) related to Eubacterium xylanophilum and Butyrivibrio spp. were strongly enriched (by five to 160 fold) over 48 h in four independent experiments performed with different faecal inocula, while nine other Firmicutes OTUs showed > 5-fold enrichment in at least one experiment. Ferulic acid was released from the wheat bran during degradation but was rapidly converted to phenylpropionic acid derivatives via hydrogenation, demethylation and dehydroxylation to give metabolites that are detected in human faecal samples. Pure culture work using bacterial isolates related to the enriched OTUs, including several butyrate-producers, demonstrated that the strains caused substrate weight loss and released ferulic acid, but with limited further conversion. We conclude that breakdown of wheat bran involves specialist primary degraders while the conversion of released ferulic acid is likely to involve a multi-species pathway.
诸如麦麸之类的谷物纤维被认为因其对肠道微生物群的影响而对人类健康有益。我们在此通过基于16S rRNA基因的群落分析表明，在厌氧发酵罐中向人类肠道微生物群落提供经淀粉酶预处理的麦麸作为唯一添加的能量来源，会导致少数细菌物种的选择性和渐进性富集。特别是，与嗜木真杆菌和丁酸弧菌属相关的未培养毛螺菌科（厚壁菌门）的操作分类单元（OTU）在使用不同粪便接种物进行的四项独立实验中，在48小时内强烈富集（富集了5至160倍），而其他九个厚壁菌门OTU在至少一项实验中显示出>5倍的富集。阿魏酸在降解过程中从麦麸中释放出来，但通过氢化、脱甲基和脱羟基迅速转化为苯丙酸衍生物，生成在人类粪便样本中检测到的代谢物。使用与富集的OTU相关的细菌分离物进行的纯培养工作，包括几种丁酸盐产生菌，表明这些菌株导致底物重量减轻并释放阿魏酸，但进一步转化有限。我们得出结论，麦麸的分解涉及专门的初级降解者，而释放的阿魏酸的转化可能涉及多物种途径。
