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Abstract
Background: Photofermentation, usually used to convert organic acids into hydrogen, has the potential capacity to effectively use a variety of feedstocks. Hydrogen production by photofermentation via immobilized reactor systems has many advantages such as avoiding cell washout at low hydraulic retention times (HRTs) and keeping high biomass inventory in the bioreactor. In this study, two newly isolated strains were entrapped in LentiKat® and the LentiKat discs were filled in an upflow reactor. The influent solution was composed of acetate and butyrate, which are the main effluents of the dark fermentation process. The effect of HRT (72, 36, 18 and 9 h) on hydrogen production and substrate concentration were monitored daily. Another upflow reactor without any immobilized material was operated at the same conditions to compare the immobilized and suspended systems. Results: Two upflow bioreactors, namely the suspended and immobilized cell reactors (biomass entrapped in LentiKat polymer) were used to compare the hydrogen production performances at varying and identical HRT conditions. Immobilized cell bioreactors showed better results even at low HRT values; on the other hand, the lower HRT values (HRT < 36 h) resulted in cell washout from the system in suspended cell bioreactors. Conclusion: The two newly isolated strains of Rubrivax gelatinosus and Stenotrophomas maltophilia were demonstrated to be good candidates for biohydrogen production from acetate and butyrate. Cell immobilization has improved the system’s performance even at low HRT values in terms of volumetric hydrogen production.
Acknowledgements
Data presented in this article were produced within the project below; however, it is only the authors of this article who are responsible for the results and discussions made herein.
Financial & competing interests disclosure
The authors wish to thank The Scientific and Technological Research Council of Turkey (Ankara, Turkey) – Environment Atmosphere Land Nature Research Group under Grant No. 111Y161 for the financial support of this study. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.
No writing assistance was utilized in the production of this manuscript.