(154h) The Impact of Surface Topography on Adhesion and Biofilm Formation of Cyanobacteria

Biomass based renewable energy production is increasingly gaining attention due to the finite nature of fossil fuels and rapid increase in CO₂ levels in the atmosphere. In this regard, cyanobacteria (blue-green algae) based third generation biofuels are considered a promising alternative to fossil fuels, mainly because of their ability to capture CO₂ as a sole carbon source to produce fuels by photosynthesis. To date, a number of fuels and high value chemicals have been produced from cyanobacteria, but their cultivation in photobioreactors (PBRs) is challenging due to fouling on the transparent inner walls of the PBRs. Fouling can affect the light transmission efficiency of the PBR materials which in turn reduce the light availability to cyanobacteria cells and overall biomass generation and biofuel productivity. In order to prevent or reduce cyanobacteria fouling, we subjected polycarbonate PBR materials to surface topography modification by direct laser interference patterning (DLIP), and investigated the antifouling ability of the modified materials using a selected cyanobacterium (genetically engineered to enhance biofuel production). Various experimental techniques were used to characterize the biofilm formation of cyanobacteria on topography modified materials, including scanning electron microscopy (SEM), contact angle measurements, bright field microscopy, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, UV-Vis spectroscopy and atomic force microscopy (AFM). The feature size and topography of the modified PBR materials were examined by AFM. The transmission efficiency of the PBR materials was reduced by 5 - 11% as a result of laser micro patterning. The biofilm formation assay revealed that, after 7 days, the mean percent area coverage of cyanobacteria was reduced by 40% on topography modified PBR materials when compared to the smooth control surface. The cyanobacteria cells showed a tendency to align across the features, when the feature size of the topography was greater than the size of the microorganisms. Surface hydrophobicity of all the patterned materials was reduced within 4 days due to the adhesion of cyanobacteria as determined from the contact angle measurements. ATR-FTIR spectroscopy revealed proteins and polysaccharides as prominent groups involved in fouling of cyanobacteria on patterned PBR materials. Overall, the PBR materials modified through DLIP in this study showed an important role of surface topography in the prevention of cyanobacteria biofilms, indicating a viable approach to engineering antifouling materials by using this technique to explore a wide range of different topographical features and sizes.

Keywords: Biofouling, Photobioreactors, Cyanobacteria, Direct Laser Interference Patterning, Antifouling.