Biohydrogen yield obtained from glucose in this study
(1.7 mol H2/mol glucose) was higher than those were
measured by Wang et al. [31], Evvyernie et al. [32], and Chong
et al. [17] who reported a hydrogen yield of 0.81 mol H2/mol
glucose, 1.1 mol H2/mol glucose and 1.18 mol H2/mol glucose,
respectively in dark fermentation by Clostridium species.
However, a number of studies were conducted that showed
higher hydrogen yield than that was obtained in this study. In
this regard, the cultivation of Clostridium tyrobutyricum JM1 on
glucose at an incubation temperature of 37 C and pH 6.3 led
to a hydrogen yield of 3.24 mol H2/mol glucose consumed [33].
It was noted that Clostridium sp. DMHC-10 produced a
hydrogen yield of 3.35 mol H2/mol glucose when batch culture
was performed at 37 C and pH 5 [34]. Research study fulfilled
by Lin et al. [35] revealed that the maximum hydrogen yield of
2.81 mol H2/mol glucose was produced when Clostridium beijerinckii
L9 was cultivated on glucose at 35 C and pH 7.2 in
dark fermentation process. Variations in hydrogen yield obtained
by hydrogen-producing microbes could be related to
the types of bacteria, culture conditions used, mode of
fermentation (batch or continuous), and type of substrate
utilized