A simple rotating annular reactor for replicated biofilm studies

The performance of two types of rotating annular reactors for the cultivation of river biofilms was compared qualitatively and quantitatively. One reactor was a commercially available system with a rotating inner solid cylinder and polycarbonate slides in the outer fixed cylinder. The other, a non-commercial system manufactured in the laboratory, had the polycarbonate slides positioned on a machined, rotating inner cylinder. Microscale comparison of the biofilms was carried out using confocal laser scanning microscopy techniques including, fluorescent nucleic acid staining, fluor conjugated lectins and autofluorescence imaging. The results obtained indicated that the reactors were similar in terms of biofilm development pattern, thickness, bacterial biomass, and exopolymer production. Significant differences were found in terms of photosynthetic biomass with the glass bodied non-commercial reactor providing more favourable conditions for algal growth than the opaque polycarbonate outer cylinder of the commercial reactor. The study indicated that a simple inexpensive reactor constructed from available components and materials, produced river biofilms similar to those obtained using a commercial system but at substantially lower cost. The availability of such inexpensive annular reactors should facilitate much needed replicated studies of biofilm development.