Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, the Netherlands.
FEMS Microbiol Ecol. 2019 Feb 1;95(2). doi: 10.1093/femsec/fiy233.
A mechanistic understanding of microbial community establishment and product formation in open fermentative systems can aid the development of bioprocesses utilising organic waste. Kinetically, a single rate-limiting substrate is expected to result in one dominant species. Four enrichment cultures were operated to ferment either xylose or glucose in a sequencing batch reactor (SBR) or a continuous-flow stirred tank reactor (CSTR) mode. The combination of 16S rRNA gene-based analysis and fluorescence in situ hybridisation revealed no complete dominance of one species in the community. The glucose-fed and xylose-fed SBR enrichments were dominated >80% by one species. Enterobacteriaceae dominated the SBRs enrichments, with Citrobacter freundii dominant for xylose and Enterobacter cloacae for glucose. Clostridium, Enterobacteriaceae and Lachnospiraceae affiliates dominated the CSTRs enrichments. Independent of substrate, SBR communities displayed 2-3 times higher biomass-specific rate of substrate uptake (qsmax) and 50% lower biomass yield on ATP, to CSTR communities. Butyrate production was linked to dominance of Clostridium and low qsmax (1.06 Cmols Cmolx-1 h-1), while acetate and ethanol production was linked to dominance of Enterobacteriaceae and Lachnospiraceae and high qsmax (1.72 Cmols Cmolx-1 h-1 and higher). Overall, more diversity than expected through competition was observed, indicating mutualistic mechanisms might shape microbial diversity.
在开放式发酵系统中，对微生物群落建立和产物形成的机制理解可以帮助利用有机废物开发生物工艺。从动力学角度来看，单一的限速底物预计会导致一种优势物种。在序批式反应器 (SBR) 或连续搅拌釜式反应器 (CSTR) 模式下，进行了四个富集培养实验，分别以木糖或葡萄糖为底物进行发酵。16S rRNA 基因分析和荧光原位杂交的结合表明，群落中没有一种物种完全占主导地位。葡萄糖和木糖喂养的 SBR 富集物中，有一个物种占主导地位>80%。肠杆菌科在 SBR 富集物中占主导地位，其中弗氏柠檬酸杆菌（Citrobacter freundii）是木糖的优势种，阴沟肠杆菌（Enterobacter cloacae）是葡萄糖的优势种。梭菌、肠杆菌科和lachnospiraceae 附属物在 CSTR 富集物中占主导地位。与底物无关，SBR 群落的基质比生物量特异性吸收速率 (qsmax) 高 2-3 倍，生物量产率对 ATP 的比产率低 50%，而 CSTR 群落的基质比生物量特异性吸收速率 (qsmax) 低 2-3 倍，生物量产率对 ATP 的比产率低 50%。但丁酸的产生与梭菌的优势和 qsmax 较低（1.06 Cmols Cmolx-1 h-1）有关，而乙酸和乙醇的产生与肠杆菌科和lachnospiraceae 的优势和 qsmax 较高（1.72 Cmols Cmolx-1 h-1 及以上）有关。总的来说，观察到的多样性比预期的通过竞争更多，这表明互惠共生机制可能会影响微生物多样性。
