Membrane fouling induced by AHL-mediated soluble microbial product (SMP) formation by fouling-causing bacteria co-cultured with fouling-enhancing bacteria

Abstract

Membrane fouling still remains a major obstacle for wider applications of membrane bioreactor (MBR), which is mainly caused by soluble microbial products (SMP). Identification of key bacteria responsible for SMP production is essential for mitigation of membrane fouling. Here, we investigated the effect of microbial interaction on membrane fouling. We measured the membrane fouling potentials of 13 bacterial strains isolated from a pilot-scale MBR treating domestic wastewater when they were cultivated as single-culture and co-culture. We found that fouling-causing bacteria (FCB) displayed much higher fouling potential when co-cultured even with non-FCB and mixed population (activated sludge). In particular, the fouling potential of strain S26, one of FCB, increased 26.8 times when cultivated with strain S22 (fouling-enhancing bacteria, FEB). The secretion of N-octanoyl-L-homoserine lactone (C8-HSL) was increased by co-cultivating S22 and S26 as compared with cultivating as single culture, which stimulated the production of fouling-causing SMP by S26 and consequently resulted in severe membrane fouling. This result suggests that AHL-mediated quorum-sensing (QS) regulatory system was involved in secretion of fouling-causing SMP.

Fouling Development in A/O-MBR under Low Organic Loading Condition and Identification of Key Bacteria for Biofilm Formations

“…To date, bacteria related to biofilm formation have been determined in various MBRs treating several kinds of wastewater. The relationship between fouling development and bacterial species that show high productivity of foulants such as EPS, SMPs, and auto-inducers, has been studied and reported previously 5 , 6 . High bacterial relative abundance, high microbial community diversity, and high productivity of foulants probably has an important role in biofilm formation 7 , 8 .…”

Complete Genome Sequence of Klebsiella quasipneumoniae Strain S05, a Fouling-Causing Bacterium Isolated from a Membrane Bioreactor

“…similipneumoniae (07A044 T , GenBank accession number CBZR000000000) ( 8 ). These results suggest that strain S05 belongs to the species K. quasipneumoniae , although strain S05 was previously considered to be most closely related to K. pneumoniae , based on the 16S rRNA gene sequence similarity of 99.5% ( 5 ).…”

“…Previously, we isolated bacterial strains responsible for membrane fouling, termed fouling-causing bacteria (FCB), from fouled membranes in a pilot-scale MBR fed with real municipal wastewater ( 4 ). One of the FCB, Klebsiella quasipneumoniae strain S05, was found to excrete soluble microbial products (SMPs) that cause severe membrane fouling ( 4 , 5 ). Interestingly, this strain is also capable of respiring on various electron accepters, including solid-state anodic electrodes and oxygen and nitrate (S. Ishizaki, P. R. Islam, H. Miyake, Y. Narita, and S. Okabe, unpublished data).…”

Quorum Sensing Signaling and Quenching in the Multidrug-Resistant Pathogen Stenotrophomonas maltophilia

“…isolated from sediments of wastewater treatment systems (Valle et al, 2004 ; Hu et al, 2016 ) and activated sludge (Tan et al, 2014 , 2015 ). Besides the Stenotrophomonas genus, AHL-activity has also been detected in other Xanthomonadaceae including Thermomonas (Ishizaki et al, 2017 ), Lysobacter (Tan et al, 2015 ) and Xanthomonas sp. (Veselova et al, 2003 ).…”