Support material dictates the attached biomass characteristics during the immobilization process in anaerobic continuous-flow packed-bed bioreactor

- Immobilization process in continuous-flow packed-bed bioreactor was investigated.
- Seven-day-operation was necessary to reach microbial and metabolic stability.
- Bacterial diversity/quantity were higher on polyethylene and expanded clay supports.
- Metabolic shift coincided with the lowest pH occurred differently between supports.
- Support material was important factor in biofilm formation and metabolic outcome.

Hydrogen is considered to be an ideal energy alternative to replace environmentally burdensome fossil fuels. For its long-term production the immobilized biofilm system is the most promising and to choose the right support material the most challenging. In this respect, the anaerobic up-flow bioreactors packed with four most used support materials (polyethylene, polyurethane, activated carbon and expanded clay) were tested to investigate the crucial bacteria sensitive period-the immobilization process. Seven-day-operation was necessary and sufficient to reach metabolic and microbial stability regardless of support material used. The support material had an influence on the microbial metabolic activity as well as on quantity and quality characteristics of the immobilized microbial community, being polyethylene and expanded clay more appropriate as supports among the materials evaluated; this could be attributed to pH alteration. The obtained results suggest that the support material dictates the outcome of the immobilization process in the anaerobic continuous-flow bioreactor.