Abstract
Hydrogen could be alternative energy carrier in the future as well as source for chemical and fuel synthesis due to its high energy content, environmentally friendly technology and zero carbon emissions. In particular, conversion of organic substrates to hydrogen via dark fermentation process is of great interest. The aim of this study was fermentative hydrogen production using anaerobic mixed culture using different carbon sources (mono and disaccharides) and further optimization by varying a number of operating parameters (pH value, temperature, organic loading, mixing intensity). Among all tested mono- and disaccharides, glucose was shown as the preferred carbon source exhibiting hydrogen yield of 1.44 mol H(2)/mol glucose. Further evaluation of selected operating parameters showed that the highest hydrogen yield (1.55 mol H(2)/mol glucose) was obtained at the initial pH value of 6.4, T=37 °C and organic loading of 5 g/L. The obtained results demonstrate that lower hydrogen yield at all other conditions was associated with redirection of metabolic pathways from butyric and acetic (accompanied by H(2) production) to lactic (simultaneous H(2) production is not mandatory) acid production. These results therefore represent an important foundation for the optimization and industrial-scale production of hydrogen from organic substrates.
Highlights
Biohydrogen is considered as one of the most promising energy carriers, many research topics focusing on renewable energy emphasize its on-site use in the chemical industry and refineries
Lower hydrogen production levels occurred in test mixtures with initial pH values below 5.8, as low pH values are known to suppress hydrogenase activity.[13]
By further lowering pH value of the fermentation broth to 4.8, hydrogen production rate and hydrogen yield decreased to only 0.34 NmL/h and 0.03 mol H2/mol glucose, respectively
Summary
Biohydrogen is considered as one of the most promising energy carriers, many research topics focusing on renewable energy emphasize its on-site use in the chemical industry and refineries. Dark fermentative hydrogen production exhibits several advantages over other biological hydrogen production processes, as it enables higher conversion yields, a wider range of substrate utilization and requires no light.[2] Fermentative hydrogen production from biomass can be attained either by mixed acidogenic microbial cultures or a pure culture of saccharolytic bacteria. Even though pure cultures have the potential to produce hydrogen at higher yields,[3] these are not suitable for large-scale biohydrogen production due to requirements of frequent reactor sterilization, ongoing substrate hygienisation and process stability issues. In terms of scale-up and industrial application, use of mixed microbial consortia is more practical than pure seed cultures, as the former allows simpler operation and utilization of a wider range of substrates
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