By comparing the experiments of Conditions 3, 4, 5 and 6, it is possible to notice that, when there was sugar concentration higher than 1 g/L, the addition of extra sugar, even changing the type of the sugar, did not favored hydrogen production. Therefore, in the assay of Condition 7, the performance of the photo-fermentation process was investigated by relaying repeatedly the carbon source (lactose and glucose), around 6.0 g/L, right after the sugar was totally consumed.