Faust L, Szendy M, Plugge C M, van den Brink P F H, Temmink H, Rijnaarts H H M
Wetsus-Centre of Excellence for Sustainable Water Technology, P.O. Box 1113, 8900 CC, Leeuwarden, The Netherlands,
Appl Microbiol Biotechnol. 2015 Jun;99(12):5327-37. doi: 10.1007/s00253-015-6402-y. Epub 2015 Jan 30.
High-loaded membrane bioreactors (HL-MBRs), i.e., bioreactors equipped with a membrane for biomass retention and operated at extremely short sludge and hydraulic retention times, can concentrate sewage organic matter to facilitate subsequent energy and chemical recovery from these organics. Bioflocculation, accomplished by microorganisms that produce extracellular polymers, is a very important mechanism in these reactors. Bacterial diversity of the sludge and supernatant fraction of HL-MBRs operated at very short sludge retention times (0.125, 0.5, and 1 day) were determined using a PCR-denaturing gradient gel electrophoresis (DGGE) and clone library approach and compared to the diversity in sewage. Already at a sludge retention time (SRT) of 0.125 day, a distinct bacterial community developed compared to the community in sewage. Bioflocculation, however, was low and the majority of the bacteria, especially Arcobacter, were present in the supernatant fraction. Upon increasing SRT from 0.125 to 1 day, a much stronger bioflocculation was accompanied by an increased abundance of Bacteroidetes in the (solid) sludge fraction: 27.5 % at an SRT of 0.5 day and 46.4 % at an SRT of 1 day. Furthermore, cluster analysis of DGGE profiles revealed that the bacterial community structure in the sludge was different from that in the supernatant. To localize specific bacterial classes in the sludge flocs, fluorescence in situ hybridization (FISH) was carried out with three different bacterial probes. This showed that Betaproteobacteria formed clusters in the sludge flocs whereas Alphaproteobacteria and Gammaproteobacteria were mainly present as single cells.
高负荷膜生物反应器（HL-MBRs），即配备用于生物量保留的膜并在极短的污泥和水力停留时间下运行的生物反应器，可以浓缩污水中的有机物，以便于随后从这些有机物中回收能量和化学品。由产生细胞外聚合物的微生物完成的生物絮凝是这些反应器中非常重要的机制。使用PCR-变性梯度凝胶电泳（DGGE）和克隆文库方法确定了在极短污泥停留时间（0.125、0.5和1天）下运行的HL-MBRs的污泥和上清液部分的细菌多样性，并与污水中的多样性进行了比较。在污泥停留时间（SRT）为0.125天时，与污水中的群落相比，形成了一个独特的细菌群落。然而，生物絮凝程度较低，大多数细菌，尤其是弓形杆菌，存在于上清液部分。当SRT从0.125天增加到1天时，更强的生物絮凝伴随着（固体）污泥部分中拟杆菌丰度的增加：SRT为0.5天时为27.5%，SRT为1天时为46.4%。此外，DGGE图谱的聚类分析表明，污泥中的细菌群落结构与上清液中的不同。为了定位污泥絮体中的特定细菌类群，使用三种不同的细菌探针进行了荧光原位杂交（FISH）。结果表明，β-变形菌在污泥絮体中形成簇，而α-变形菌和γ-变形菌主要以单细胞形式存在。
