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Research article

Article

Research article

J. Microbiol. Biotechnol. 2015; 25(11): 1908-1919

Published online November 28, 2015 https://doi.org/10.4014/jmb.1506.06010

Copyright © The Korean Society for Microbiology and Biotechnology.

Combined Effects of Curcumin and (–)-Epigallocatechin Gallate on Inhibition of N-Acylhomoserine Lactone-Mediated Biofilm Formation in Wastewater Bacteria from Membrane Bioreactor

Harshad Lade 1, Diby Paul 1 and Ji Hyang Kweon 1*

Water Treatment and Membrane Laboratory, Department of Environmental Engineering, Konkuk University, Seoul 143-701, Republic of Korea

Received: June 4, 2015; Accepted: June 30, 2015

Abstract

This work investigated the potential of curcumin (CCM) and (–)-epigallocatechin gallate
(EGCG) to inhibit N-acyl homoserine lactone (AHL)-mediated biofilm formation in gramnegative
bacteria from membrane bioreactor (MBR) activated sludge. The minimum inhibitory
concentrations (MICs) of CCM alone against all the tested bacteria were 200-350 μg/ml,
whereas those for EGCG were 300-600 μg/ml. Biofilm formation at one-half MICs indicated
that CCM and EGCG alone respectively inhibited 52-68% and 59-78% of biofilm formation
among all the tested bacteria. However, their combination resulted in 95-99% of biofilm
reduction. Quorum sensing inhibition (QSI) assay with known biosensor strains demonstrated
that CCM inhibited the expression of C4 and C6 homoserine lactones (HSLs)-mediated
phenotypes, whereas EGCG inhibited C4, C6, and C10 HSLs-based phenotypes. The Center for
Disease Control biofilm reactor containing a multispecies culture of nine bacteria with onehalf
MIC of CCM (150 μg/ml) and EGCG (275 μg/ml) showed 17 and 14 μg/cm2 of
extracellular polymeric substances (EPS) on polyvinylidene fluoride membrane surface,
whereas their combination (100 μg/ml of each) exhibited much lower EPS content (3 μg/cm2).
Confocal laser scanning microscopy observations also illustrated that the combination of
compounds tremendously reduced the biofilm thickness. The combined effect of CCM with
EGCG clearly reveals for the first time the enhanced inhibition of AHL-mediated biofilm
formation in bacteria from activated sludge. Thus, such combined natural QSI approach could
be used for the inhibition of membrane biofouling in MBRs treating wastewaters.

Keywords: Curcumin, (–,)-epigallocatechin gallate, quorum sensing inhibition, biofilm formation, wastewater treatment, membrane bioreactor