Macroencapsulation of quorum quenching bacteria by polymeric membrane layer and its application to MBR for biofouling control

We report the preparation and characterization of macrocapsules coated by a polymeric membrane layer for the stable encapsulation of quorum quenching (QQ) bacteria (Rhodococcus sp. BH4). As a new macrocapsule manufacturing platform, a phase inversion method was adopted to cover an alginate core with a microporous membrane layer of poly(vinylidene) fluoride (PVDF), polyethersulfone (PES) or polysulfone (PSf). Scanning electron microscopy revealed that membrane layer was successfully formed on the outside of the alginate-QQ bacteria matrix. Although contact with the organic solvent during the phase inversion step caused minor cell damage, the QQ activity of macrocapsules could be reactivated through cultivation. The QQ bacteria entrapping macrocapsules showed an excellent anti-biofouling capacity in the continuous membrane bioreactor (MBR) fed even with real wastewater. The macrocapsules were capable of maintaining QQ activity more safely than previously reported alginate beads under harsher environmental conditions such as in real wastewater or in the presence of chelating agent (EDTA) which can disintegrate an alginate matrix. Particularly, the PSf coated membrane layer was pronounced in preventing QQ bacteria from leaking outside the macrocapsules. This study is expected to bring the bacterial QQ closer to being a practical solution to the biofouling problem in MBR for wastewater treatment. (C) 2014 Elsevier B.V. All rights reserved,