Microbial community regulation and performance enhancement in gas biofilters by interrupting bacterial communication

Abstract

Background Controlling excess biomass accumulation and clogging is important for maintaining the performance of gas biofilters and reducing energy consumption. Interruption of bacterial communication (quorum quenching) can modulate gene expression and alter biofilm properties. However, whether the problem of excess biomass accumulation in gas biofilters can be addressed by interrupting bacterial communication remains unknown. Results In this study, parallel laboratory-scale gas biofilters were operated with Rhodococcus sp. BH4 (QQBF) and without Rhodococcus sp. BH4 (BF) to explore the effects of quorum quenching (QQ) bacteria on biomass accumulation and clogging. QQBF showed lower biomass accumulation (109 kg/m3) and superior operational stability (85–96%) than BF (170 kg/m3; 63–92%) at the end of the operation. Compared to BF, the QQBF biofilm had lower adhesion strength and decreased extracellular polymeric substance production, leading to easier detachment of biomass from filler surface into the leachate. Meanwhile, the relative abundance of quorum sensing (QS)-related species was found to decrease from 67 (BF) to 56% (QQBF). The QS function genes were also found a lower relative abundance in QQBF, compared with BF. Moreover, although both biofilters presented aromatic compounds removal performance, the keystone species in QQBF played an important role in maintaining biofilm stability, while the keystone species in BF exhibited great potential for biofilm formation. Finally, the possible influencing mechanism of Rhodococcus sp. BH4 on biofilm adhesion was demonstrated. Overall, the results of this study achieved excess biomass control while maintaining stable biofiltration performance (without interrupting operation) and greatly promoted the use of QQ technology in bioreactors. Graphical Abstract

Improving Biofilm Formation and Bioreactor Startup at Low Temperature through Regulating Microbial Community Communication and Stability

“…To verify the effect of spermidine on the formation of biofilm and the performance of the reactor at low temperatures, two sets of gaseous toluene treatment biofilters, named control biofilter (CBF) and treatment biofilter (TBF), were established and operated at 15 °C. The construction of biofilters is as described in our previous studies. , Briefly, about 1 L of filler was filled into a 1.3 L acrylic glass biofilter with a height of 45 cm. The same sludge used in Section was cultivated for 7 days using liquid toluene and then inoculated into the two biofilters.…”

“…Activated sludge from the secondary sedimentation tank (Tianjin Jinnan Wastewater Treatment Plant) was selected as the model system for biofilm formation since it is one of the most common inoculated sludges . The biofilm formation experiment was set up as described in our previous studies. , Specifically, the collected activated sludge was aerated for 3 days, and the concentration of chemical oxygen demand was monitored to indicate the depletion of the original carbon source. Then the activated sludge was washed 3 times with buffered saline solution (0.9% NaCl, pH = 7) and added to two sets of 250 mL Erlenmeyer flasks (namely Control (without spermidine) and Treatment (with spermidine); optical density: 1.0) and incubated for 48 h at 15 °C and 120 rpm.…”

“…The construction of biofilters is as described in our previous studies. 15,18 Briefly, about 1 L of filler was filled S1. The performance, including removal efficiencies (RE) and elimination capacity (EC), and biomass accumulation were monitored during the operation.…”

“…To date, several attempts have been made to mitigate the impact of low temperature on biofilm formation, including the installation of temperature controllers, construction of cometabolism systems, and regulation of microbial communities. 13,15 Among these approaches, microbial community regulation has drawn great attention because it could achieve engineering objectives through the regulation of biofilm characteristics. 16−18 For instance, the exogenous addition of signal molecules based on the quorum sensing (QS) principle has been proven to promote the formation and activity of biofilms at low temperatures.…”

“…To date, several attempts have been made to mitigate the impact of low temperature on biofilm formation, including the installation of temperature controllers, construction of cometabolism systems, and regulation of microbial communities. , Among these approaches, microbial community regulation has drawn great attention because it could achieve engineering objectives through the regulation of biofilm characteristics. − For instance, the exogenous addition of signal molecules based on the quorum sensing (QS) principle has been proven to promote the formation and activity of biofilms at low temperatures . Biomass accumulation in gas biofilters and the activity of anammox biofilm have been significantly improved through the exogenous addition of N -acyl-homoserine lactones (AHLs). , However, the high cost of signal molecules has become the main factor restricting their large-scale application.…”