Highlights 1) Hydrogen produced by dark fermentation based on repeated-batch cycles 2) Extension superior to 900 h was succeeded with alternated cycles of sugars 3) Maximum H2 yield (3.4 mol H2/mol hexose) resulted from alternated addition of sugars 4) Maximum hydrogen productivity was 168.27 mmol H2/L/day in 24 h of process
5) Microorganisms followed the butyric-type fermentation
AbstractHydrogen is considered a very clean energy source, since its combustion releases mainly water as a reaction product. Besides, it has the advantage of having the highest energy density when compared to any other fuel. This work studied the hydrogen production applying dark fermentation by a heat shock pre-treated microbial 2 consortium. A repeated batch cycle operation was evaluated by adding glucose or lactose in an isolated, alternated or simultaneous ways, in order to keep the production of hydrogen for a longer time. Fermentations with simultaneous addition of glucose and lactose promoted maximum productivity of 168.27 mmol H2·L -1 ·day -1 . Nevertheless, the alternation of two carbon source (glucose and lactose) allowed keeping the culture active with potential to hydrogen production for a period of time higher than 900 h. At the end of fermentation, the main products were lactic acid and butyric acid, followed by acetic acid, ethanol and propionic acid.
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