Project 8: Signalling and constitutive compounds of biofilms as targets to prophylaxis/remediation of bio-fouling during cultivation of planktonic microalgae in a closed photobioreactor system

This is an industry-based project which is examining strategies for preventing the build-up and removal of biofilms at the liquid to plastic polymer surface interface during the (non-axenic) cultivation of Nannochchloropsis sp. in the proprietary ProviAPT photobioreactors. Although data is available on bacterial communities in Nannochloropsis open production systems, little is known about the origin and nature of bio-films occuring in closed photo-bioreactors such as the proprietary ProviAPT system.

Javier Giraldo has been appointed researcher this project. Based at Proviron in Belgium, Javier’s research is aimed at the identification of;

  • Signalling molecules/bactericidal compounds that can be manipulated or used to prevent biofouling;
  • Biological (bacterial) and biochemical (biofilm matrix) targets for biofilm removal; and
  • Operating conditions and nutrient recipes resulting in reduced biofouling.

There is a considerable overlap between this project and project 7. Project 8, however, focuses on planktonic algae rather than benthic diatom species. Its results will provide input to  project 7, for example, through the portfolio of compounds to be tested on biofilm formation, through new polymer formulations, or the identification of generic solutions for polymer coating.

It is noted that seasonal light variations are accompanied by marked changes in the bacterial load of algae cultures; during spells of high insolation, biofilm formation seems delayed and in some cases sloughing is observed. Identifying both the nature and the mechanisms governing the build-up of these biofilms should enable us to devise (prophylactic) strategies to control or remediate them. To this end, project 8 will investigate the bacterial composition and matrix components of biofilms, helped by research to be undertaken at SAMS and FSU Jena. In parallel, the evolution of candidate signalling molecules involved in biofilm formation, for example, both Nannochloropsis sp. and Isochrysis sp. have been reported to produce compounds affecting quorum-sensing (QS) or quorum-quenching (QQ). Presumed bactericidal compounds will be investigated both during industrial production campaigns and under controlled lab-cultivation.

This screening and characterisation of QS/QQ activity or biofilm destabilizing activity will be performed through a close collaboration with researchers at the UGent and FSU JENA according to the methodology acquired through the work of project 7. Finally, based on the results obtained, a limited number of candidate biofilm destabilizing agents will be selected and tested further. Operating conditions and nutrient recipes will be adjusted so as to manipulate their presence, while both biofilm formation/composition and algae productivity are followed.