A simple rotating annular reactor for replicated biofilm studies

The performance of two types of rotating annular reactors for the cultivati on of river biofilms was compared qualitatively and quantitatively. One rea ctor was a commercially available system with a rotating inner solid cylind er and polycarbonate slides in the outer fixed cylinder. The other, a non-c ommercial system manufactured in the laboratory, had the polycarbonate slid es positioned on a machined, rotating inner cylinder. Microscale comparison of the biofilms was carried out using confocal laser scanning microscopy t echniques including, fluorescent nucleic acid staining, fluor conjugated le ctins 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-commerci al reactor providing more favourable conditions for algal growth than the o paque polycarbonate outer cylinder of the commercial reactor. The study ind icated that a simple inexpensive reactor constructed from available compone nts and materials, produced river biofilms similar to those obtained using a commercial system but at substantially lower cost. The availability of su ch inexpensive annular reactors should facilitate much needed replicated st udies of biofilm development. (C) 2000 Elsevier Science BN. All lights rese rved.