Effects of the surface physico-chemical properties and the surface textures on the initial colonization and the attached growth in algal biofilm

Background: Algal biofilm reactors represent a promising cultivation system that can economically produce biomass without the need for expensive harvesting operations. A critical component of algal biofilm systems is the material used for attachment. This research reports a comprehensive study of the effects of material surface physicochemical properties, the surface texture, and their interactions on the initial colonization and the long-term attached growth in algal biofilm systems. A total of 28 materials with a smooth surface were tested for initial cell colonization and it was found that the tetradecane contact angle of the materials had a good correlation with cell attachment. The effects of surface texture were evaluated using mesh materials (nylon, polypropylene, high-density polyethylene, polyester, aluminum, and stainless steel) with openings ranging from 0.05 to 6.40 mm. Results: The mesh materials with an opening of 0.5 mm resulted in the highest attachment. The interaction of surface physico-chemical properties and surface texture, and their co-effects on the cell attachment, was quantitatively described using a second-order polynomial regression. The long-term algal attached growth for the different materials showed a trend similar to that found in initial colonization. Conclusions: Collectively, nylon and polypropylene mesh with 0.50-1.25 mm openings resulted in the best initial colonization and long-term attached growth, with a 28-30 g m(-2) biomass yield and 4.0-4.3 g m(-2) day biomass productivity being achieved on a pilot-scale revolving algal biofilm system.