Department of Chemistry and Biotechnology, Tallinn University of Technology, 19086, Tallinn, Estonia; Center of Food and Fermentation Technologies, 12618, Tallinn, Estonia.
Department of Chemistry and Biotechnology, Tallinn University of Technology, 19086, Tallinn, Estonia.
Anaerobe. 2018 Aug;52:100-110. doi: 10.1016/j.anaerobe.2018.06.009. Epub 2018 Jun 20.
The aim of the study was to investigate the metabolism of non-digestible oligo- and polysaccharides by fecal microbiota, using isothermal microcalorimetry. The five tested substrates were raffinose, melibiose, a mixture of oligo- and polysaccharides produced from raffinose by levansucrase, levan synthesized from raffinose, and levan from timothy grass. Two inocula were comprised of pooled fecal samples from overweight or normal-weight children, from healthy adult volunteers and a pure culture of Bacteroides thetaiotaomicron as a reference bacterium for colon microbiota. The growth was analyzed based on the heat evolution curves, and the production of organic acids and gases. Taxonomic profiles of the microbiota were assessed by 16S rDNA sequencing. Raffinose and melibiose promoted the growth of bifidobacteria in all fecal pools. Several pool-specific substrate-related responses to raffinose and melibiose were revealed. Lactate-producing bacteria (Streptococcus and Enterococcus) became enriched in the pool of overweight children resulting in lactic acid as the major fermentation product on short saccharides. Acetic and butyric acids were prevalent at fermentation in the normal-weight pool coinciding with the enrichment of Catenibacterium. In the adult pool, the specific promotion of Bacteroides and Lachnospiraceae by levans was disclosed. In the fecal pool of normal-weight children, levans stimulated the growth of Senegalimassilia and Lachnoclostridium and this particular pool also showed the highest maximum heat production rate at levan fermentation. Levans and raffinose-derived oligosaccharides, but not raffinose and melibiose were completely fermented by a pure culture of Bacteroides thetaiotaomicron. The main conclusion from the study is that fecal microbiota of normal and overweight children have different compositions and they respond in specific manners to non-digestible oligo- and polysaccharides: raffinose, melibiose, raffinose-derived oligosaccharides and levans. The potential of the tested saccharides to support a healthy balance of colon microbiota requires further studies.
本研究旨在利用等温微量热法研究膳食纤维代谢物在肠道微生物群中的代谢。五种测试底物为棉子糖、密二糖、由棉子糖经蔗糖酶产生的低聚糖和多糖混合物、由棉子糖合成的莱鲍迪苷以及来自梯牧草的莱鲍迪苷。两种接种物由超重或正常体重儿童、健康成年志愿者的粪便样本混合而成，并以纯培养的拟杆菌属（Bacteroides thetaiotaomicron）作为结肠微生物群的参考细菌。通过热演化曲线和有机酸及气体的产生来分析生长情况。通过 16S rDNA 测序评估微生物群的分类组成。棉子糖和密二糖促进了所有粪便样本中双歧杆菌的生长。在棉子糖和密二糖方面，揭示了几种与粪便样本相关的底物特异性反应。产乳酸细菌（链球菌属和肠球菌属）在超重儿童的粪便样本中富集，导致短链糖发酵的主要产物为乳酸。在正常体重儿童的粪便样本中，与 Catenibacterium 富集相一致的是，乙酸和丁酸是主要发酵产物。在成年粪便样本中，发现莱鲍迪苷特异性促进拟杆菌属和毛螺菌科的生长。在正常体重儿童的粪便样本中，莱鲍迪苷刺激 Senegalimassilia 和 Lachnoclostridium 的生长，且该粪便样本在莱鲍迪苷发酵时表现出最高的最大产热率。在纯培养的拟杆菌属中，莱鲍迪苷和棉子糖衍生的低聚糖，但不是棉子糖和密二糖，可被完全发酵。本研究的主要结论是，正常和超重儿童的粪便微生物群具有不同的组成，它们对非消化性低聚糖和多糖（棉子糖、密二糖、棉子糖衍生的低聚糖和莱鲍迪苷）有特定的反应。需要进一步研究这些测试糖在支持结肠微生物群健康平衡方面的潜力。
