Department of Biological Sciences, Marquette University, Wehr Life Sciences Building, P.O. Box 1881, Milwaukee, WI, 53201-1881, USA.
BioTechnology Institute, University of Minnesota, St. Paul, MN, 55108, USA.
Appl Microbiol Biotechnol. 2020 May;104(10):4563-4575. doi: 10.1007/s00253-020-10552-9. Epub 2020 Mar 26.
Buildup of volatile fatty acids (VFAs) in anaerobic digesters (ADs) often results in acidification and process failure. Understanding the dynamics of microbial communities involved in VFA degradation under stable and overload conditions may help optimize anaerobic digestion processes. In this study, five triplicate mesophilic completely mixed AD sets were operated at different organic loading rates (OLRs; 1-6 g chemical oxygen demand [COD] Lday), and changes in the composition and abundance of VFA-degrading microbial communities were monitored using amplicon sequencing and taxon-specific quantitative PCRs, respectively. AD sets operated at OLRs of 1-4 g COD Lday were functionally stable throughout the operational period (120 days) whereas process instability (characterized by VFA buildup, pH decline, and decreased methane production rate) occurred in digesters operated at ≥ 5 g COD Lday. Though microbial taxa involved in propionate (Syntrophobacter and Pelotomaculum) and butyrate (Syntrophomonas) degradation were detected across all ADs, their abundance decreased with increasing OLR. The overload conditions also inhibited the proliferation of the acetoclastic methanogen, Methanosaeta, and caused a microbial community shift to acetate oxidizers (Tepidanaerobacter acetatoxydans) and hydrogenotrophic methanogens (Methanoculleus). This study's results highlight the importance of operating ADs with conditions that promote the maintenance of microbial communities involved in VFA degradation.
在厌氧消化器 (AD) 中，挥发性脂肪酸 (VFAs) 的积累常常导致酸化和工艺失败。了解在稳定和过载条件下参与 VFA 降解的微生物群落的动态，可能有助于优化厌氧消化过程。在这项研究中，五个重复的中温完全混合 AD 系统在不同的有机负荷率 (OLR；1-6 g 化学需氧量 [COD] L 天) 下运行，通过扩增子测序和分类特异性定量 PCR 分别监测 VFA 降解微生物群落的组成和丰度变化。在 OLR 为 1-4 g COD L 天的 AD 系统在整个运行期间（120 天）功能稳定，而在 OLR 为≥5 g COD L 天的消化器中出现了工艺不稳定（表现为 VFA 积累、pH 值下降和甲烷生成速率降低）。尽管参与丙酸（Syntrophobacter 和 Pelotomaculum）和丁酸（Syntrophomonas）降解的微生物类群在所有 AD 中均被检测到，但它们的丰度随着 OLR 的增加而降低。过载条件还抑制了产乙酸甲烷菌 Methanosaeta 的增殖，并导致微生物群落向乙酸氧化菌（Tepidanaerobacter acetatoxydans）和氢营养型甲烷菌（Methanoculleus）转移。本研究结果强调了在有利于维持参与 VFA 降解的微生物群落的条件下运行 AD 的重要性。
