Essential roles of eDNA and AI-2 in aerobic granulation in sequencing batch reactors operated at different settling times |
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Authors: | Yanghui Xiong Yu Liu |
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Institution: | (1) Division of Environmental and Water Resources Engineering, School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore; |
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Abstract: | Settling time has been considered as one of the most effective selection pressures for aerobic granulation in sequencing batch
reactors (SBRs), i.e., poorly settleable bioparticles would be washed out from SBRs, and the heavy and good settling ones
would be retained at a shorter setting time. However, its biological implication remains unclear. This study investigated
the microbiological mechanisms of aerobic granulation at different settling times. It provided experimental evidence for the
first time showing that a shorter settling time could enhance release of extracellular DNA through cell lysis, which in turn
initiated microbial aggregation leading to increased biomass size and density, while AI-2-mediated quorum sensing was found
not to be involved in initial aggregation. It was further shown that the AI-2-mediated quorum sensing system was activated
to regulate the growth and maturation of aerobic granules when the biomass density reached a threshold of 1.025 g ml−1. It appears from this study that a short settling time of SBR would induce microbiological and physiological responses of
bacteria which are required at different stages of aerobic granulation and provide new insights into biological mechanisms
of settling time-triggered aerobic granulation. |
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Keywords: | |
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