초록
<P><B>Abstract</B></P> <P>The objective of this study was to enhance the hydrogen production rate of dark fermentation in batch operation. For the first time, the hyperthermophilic pure culture of <I>Thermotoga neapolitana cf. Capnolactica</I> was applied at elevated biomass concentrations. The increase of the initial biomass concentration from 0.46 to 1.74 g cell dry weight/L led to a general acceleration of the fermentation process, reducing the fermentation time of 5 g glucose/L down to 3 h with a lag phase of 0.4 h. The volumetric hydrogen production rate increased from 323 (±11) to 654 (±30) mL/L/h with a concomitant enhancement of the biomass growth and glucose consumption rate. The hydrogen yield of 2.45 (±0.09) mol H<SUB>2</SUB>/mol glucose, the hydrogen concentration of 68% in the produced gas and the composition of the end products in the digestate, i.e. 62.3 (±2.5)% acetic acid, 23.5 (±2.9)% lactic acid and 2.3 (±0.1)% alanine, remained unaffected at increasing biomass concentrations.</P> <P><B>Highlights</B></P> <P> <UL> <LI> An increase of biomass concentration from 0.46 to 1.74 g/L reduced the fermentation time from 7 to 3 h. </LI> <LI> The hydrogen production rate reached up to 654 (±30) mL/L/h at a biomass concentration of 1.74 g/L. </LI> <LI> The specific hydrogen production rate decreased with increasing biomass concentration. </LI> <LI> Hydrogen yield and end product composition were not affected by biomass concentration. </LI> <LI> The concentration of hydrogen in the produced gas was 67.6 (±2.4)%. </LI> </UL> </P>