title: Biodegradation of microcystins during gravity-driven membrane (GDM) ultrafiltration.
abstract: Gravity-driven membrane (GDM) ultrafiltration systems require little maintenance: they operate without electricity at ultra-low pressure in dead-end mode and without control of the biofilm formation. These systems are already in use for water purification in some regions of the world where adequate treatment and distribution of drinking water is not readily available. However, many water bodies worldwide exhibit harmful blooms of cyanobacteria that severely lower the water quality due to the production of toxic microcystins (MCs). We studied the performance of a GDM system during an artificial Microcystis aeruginosa bloom in lake water and its simulated collapse (i.e., the massive release of microcystins) over a period of 21 days. Presence of live or destroyed cyanobacterial cells in the feed water decreased the permeate flux in the Microcystis treatments considerably. At the same time, the microbial biofilms on the filter membranes could successfully reduce the amount of microcystins in the filtrate below the critical threshold concentration of 1 µg L(-1) MC for human consumption in three out of four replicates after 15 days. We found pronounced differences in the composition of bacterial communities of the biofilms on the filter membranes. Bacterial genera that could be related to microcystin degradation substantially enriched in the biofilms amended with microcystin-containing cyanobacteria. In addition to bacteria previously characterized as microcystin degraders, members of other bacterial clades potentially involved in MC degradation could be identified.
authors.affiliation: Limnological Station, Institute of Plant Biology, University of Zurich, Kilchberg, Switzerland.
authors.forename: Esther
authors.initials: E
authors.lastname: Kohler
authors.affiliation: Limnological Station, Institute of Plant Biology, University of Zurich, Kilchberg, Switzerland.
authors.forename: Jörg
authors.initials: J
authors.lastname: Villiger
authors.affiliation: Limnological Station, Institute of Plant Biology, University of Zurich, Kilchberg, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Posch
authors.affiliation: Eawag: Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Derlon
authors.affiliation: Limnological Station, Institute of Plant Biology, University of Zurich, Kilchberg, Switzerland.
authors.forename: Tanja
authors.initials: T
authors.lastname: Shabarova
authors.affiliation: Eawag: Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland; Institute of Environmental Engineering, ETH Zurich, Zurich, Switzerland.
authors.forename: Eberhard
authors.initials: E
authors.lastname: Morgenroth
authors.affiliation: Limnological Station, Institute of Plant Biology, University of Zurich, Kilchberg, Switzerland.
authors.forename: Jakob
authors.initials: J
authors.lastname: Pernthaler
authors.affiliation: Limnological Station, Institute of Plant Biology, University of Zurich, Kilchberg, Switzerland.
authors.forename: Judith F
authors.initials: JF
authors.lastname: Blom
mesh_terms: D001673:Biodegradation, Environmental; D018441:Biofilms / Q000254:growth & development; D004784:Environmental Monitoring; D006112:Gravitation; D060106:Lakes / Q000382:microbiology*; D052998:Microcystins / Q000302:isolation & purification / Q000378:metabolism*; D046931:Microcystis / Q000254:growth & development* / Q000302:isolation & purification / Q000378:metabolism; D014462:Ultrafiltration / Q000295:instrumentation*; D018508:Water Purification / Q000295:instrumentation*
chemical_list: D052998:Microcystins; C078588:microcystin