Prevention of biofilm growth on man-made surfaces: evaluation of antialgal activity of two biocides and photocatalytic nanoparticles

Abstract

As algal growth on man-made surfaces impacts their appearance, biocides and surfaces with self-cleaning properties are widely used in the building and paint industries. The objective of this study was to evaluate the antialgal activity of two biocides (triazine and isothiazoline) and photocatalytic nanoparticles of zinc oxide (20–60 nm). An aeroterrestrial green, microalgal strain of the genus Stichococcus was chosen as the test organism. By comparing a set of different structural and physiological performance parameters, lethal and also sublethal (chronic) effects were determined. Even though the herbicide triazine effectively inhibited growth (EC50 = 1.6 μmol l⁻¹) and photosynthetic performance, structural properties (eg membrane integrity) were unaffected at the EC100 (250 μmol l⁻¹), hence this herbicide did not kill the algal cells. In contrast, and due to their multiple modes of action, isothiazoline and the photocatalytic nanoparticles (the latter activated with low UV radiation) severely impacted all performance and structural parameters.

Keywords:

• aeroterrestrial algae
• growth prevention
• effectivity tests
• biocides
• photocatalysis

Acknowledgements

The authors thank Dr Constanze Messal (CEO) from MICOR Gesellschaft für mikrobielle Prozesse und Materialkunde mbH for her support. Furthermore, they are grateful to Solvig Görs who helped with the HPLC. They thank Jana Wölfel profusely for her help with the optodes. This study was supported by grants from the Max-Buchner-Stiftung and the Ministry of Education, Science and Culture Mecklenburg-Vorpommern, Germany.