title: Impacts of hydrophilic colanic acid on bacterial attachment to microfiltration membranes and subsequent membrane biofouling.
abstract: In order to examine the interactions between physicochemical properties of specific extracellular polymeric substances (EPS) and membrane biofouling, we investigated the impacts of hydrophilic colanic acid, as a model extracellular polysaccharide component, on initial bacterial attachment to different microfiltration (MF) membranes and membrane biofouling by using Escherichia coli strains producing different amounts of colanic acid. In a newly designed microtiter plate assay, the bacterial attachment by an E. coli strain RcsF(+), which produces massive amounts of colanic acid, decreased only to a hydrophobic membrane because the colanic acid made cell surfaces more hydrophilic, resulting in low cell attachment to hydrophobic membranes. The bench-scale cross-flow filtration tests followed by filtration resistance measurement revealed that RcsF(+) caused severe irreversible membrane fouling (i.e., pore-clogging), whereas less extracellular polysaccharide-producing strains caused moderate but reversible fouling to all membranes used in this study. Further cross-flow filtration tests indicated that colanic acid liberated in the bulk phase could rapidly penetrate pre-accumulated biomass layers (i.e., biofilms) and then directly clogged membrane pores. These results indicate that colanic acid, a hydrophilic extracellular polysaccharide, and possible polysaccharides with similar characteristics with colanic acid are considered as a major cause of severe irreversible membrane fouling (i.e., pore-clogging) regardless of biofilm formation (dynamic membrane).
authors.affiliation: Division of Environmental Engineering, Faculty of Engineering, Hokkaido University, North-13, West-8, Kita-ku, Sapporo, Hokkaido, 060-8628, Japan.
authors.forename: Keitaro
authors.initials: K
authors.lastname: Yoshida
authors.affiliation: Division of Environmental Engineering, Faculty of Engineering, Hokkaido University, North-13, West-8, Kita-ku, Sapporo, Hokkaido, 060-8628, Japan; Department of Applied Chemistry and Biochemical Engineering, Graduate School of Engineering, Shizuoka University, 3-5-1, Johoku, Naka-ku, Hamamatsu, Shizuoka, 432-8561, Japan.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Tashiro
authors.affiliation: Division of Environmental Engineering, Faculty of Engineering, Hokkaido University, North-13, West-8, Kita-ku, Sapporo, Hokkaido, 060-8628, Japan.
authors.forename: Thithiwat
authors.initials: T
authors.lastname: May
authors.affiliation: Division of Environmental Engineering, Faculty of Engineering, Hokkaido University, North-13, West-8, Kita-ku, Sapporo, Hokkaido, 060-8628, Japan. Electronic address: sokabe@eng.hokudai.ac.jp.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Okabe
mesh_terms: D001422:Bacterial Adhesion; D018441:Biofilms; D057219:Biofouling; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D005374:Filtration / Q000295:instrumentation*; D057927:Hydrophobic and Hydrophilic Interactions; D008567:Membranes, Artificial; D030781:Organisms, Genetically Modified; D011134:Polysaccharides / Q000737:chemistry*
chemical_list: D008567:Membranes, Artificial; D011134:Polysaccharides; C004275:colanic acid
keywords: Bacterial attachment; Colanic acid; Extracellular polymeric substances (EPS); Membrane fouling