Evaluation of different support materials used with a photo-fermentative consortium for hydrogen production

• Supports for immobilization of photobacteria for H2 production were tested.
• The photofermentative consortium was mainly composed of R. palustris.
• H2 production depended on the cell concentration attached to the support.
• Luffa fibers was the best support allowing the highest quantity of fixed biomass.

Three different support materials were evaluated for immobilization of a consortium of purple non-sulfur bacteria producing hydrogen gas. The inoculum was obtained from a bioelectrochemical system, and it was subsequently enriched. Molecular analysis showed that the consortium was mainly composed of Rhodopseudomonas palustris. The tested materials included acrylic rods, high-density polyethylene cylinders and luffa (dispersed fibers and cubes). The hydrogen production, using volatile fatty acids as the substrate, was evaluated in continuously illuminated reactors (7 klux) at 32 °C. The hydrogen production rate observed was between 14 and 20 mL H2/g VS/h. Dispersed luffa fibers showed the highest amount of immobilized biomass (19.6 ± 1.5 mg VS/cm3) followed by luffa in cubes, high-density polyethylene cylinders, and acrylic bars. The dispersed luffa fibers allowed for a better light distribution and contact with the media than the luffa in cubes. There was no significant difference in hydrogen production among the three support materials (luffa, acrylic bars or polyethylene) when the same amount of immobilized biomass was used. The luffa in fibers was the most suitable support for the purple non-sulfur consortium because of the highest area/volume ratio, biomass attachment as well as the adequate light distribution.