Selection of a support medium for a fixed-film green sulphur bacteria reactor

The ability of green sulphur bacteria (Chlorobium limicola) to grow on six different transparent plastic tube materials (PTMs) was tested to determine which material would be best as a support medium in a fixed-film bioreactor. The materials were: Bev-a-Line (polyethylene liner with ethyl vinyl acetate shell), FEP (fluorinated ethylene propylene), Kynar (polyvinylidene fluoride), PFA (perfluoroalkoxy), polypropylene and Tygon (vinyl chloride–vinylidene chloride co-polymer). The materials were soaked in water, autoclaved and added to sterile liquid growth medium. 3 to 7 days after inoculating, the bacteria concentrations in the liquid and on the PTM were measured. There was no distinction in total growth between those tubes with and those without PTMs. In comparing bacteria growth on the PTMs, the fraction of the total growth that was on the tubing was significantly higher for Tygon (1.7%) and Bev-a-line (0.6%) tubing than the other PTMs. In terms of bacteriochlorophyll (bchl) per surface area, again Tygon and Bev-a-line tubing were superior to the other PTMs tested with 220 and 81 mg bchl per square metre of tubing surface area, respectively.