The Condition 7 was carried out in order to investigate if the
proposal of interchanging the type of sugar is enough to alter the
metabolic route of the bacterium and, consequently, the composition
of the medium with the purpose of minimizing possible inhibition
effects of the photo-fermentation medium and,
consequently, extending the evolution process of hydrogen with
high productivity. The initial composition of DFE supplemented
with lactose used as substrate in the photo-fermentation test (Condition
7) was 9.31 g/L of lactose, 14.12 g/L of lactic acid, 0.71 g/L of
formic acid, 1.21 g/L of acetic acid, 4.61 g/L of butyric acid and
2.53 g/L of propionic acid. The temperature was 35 ± 3 C and the
initial cell concentration was 0.53 gvs/L. The volume of the medium
was maintained constant in 700 mL by the replacement with new
medium with the same initial composition, except the sugar and
the results are presented in Fig. 3.