As seen in Table 1, C. butyricum and the heat treated LE37 and
LE58 cultures were able to produce H2 from the microalgal biomass. The H2 yields determined for LE37 by using 10 and 25 g/L
of S. obliquus biomass were remarkably low compared to that
obtained with 50 g/L (1.52 mol/mol), certainly due to the low sugar
concentration. The increase of the biomass feedstock load and the
consequent increment in the available soluble sugars supported a
major raise of H2 production, becoming comparable to that produced by the pure strain. LE37 attained a maximum of 34.8 mL/g
vs when using 50 g/L of S. obliquus biomass whereas C. butyricum
achieved the highest production of 35 mL/g vs corresponding to a
H2 yield of 1.44 mol/mol (Table 1). Both values are higher than
the ones referred in the literature for the fermentation of microalgal biomass without previous hydrolytic pretreatment. Yun and
co-workers [40] achieved values as high as 30.74 mL/g dw in the fermentation of Chlorella vulgaris biomass by mixed cultures. In
another study, this microalga was also used to produce bioH2 with
a slightly lower value, 10.8 mL/g dw [41], whereas in the fermentation of Dunaliella tertiolecta biomass the authors achieved a
H2 production of 12.6 mL/g dw.