Unraveling optimum culture composition for hydrogen and 5-aminolevulinic acid production by Rhodobacter sphaeroides O.U.001

Abstract

The objective of this work was to reveal optimum culture composition for hydrogen and 5aminolevulinic acid productions by Rhodobacter sphaeroides O.U.001 regarding substrate concentration and supplementations of elements and vitamins. Acetate was chosen as carbon source and five distinct concentrations (20, 25, 30, 35 and 40 mM) were tested in two experimental setups. While, elements (FeSO4, 2 g L-1 and Na2MoO4.2H2O, 0.2 g L-1) and vitamins (Biotin, 0.015 g L-1 , Niacin, 0.5 g L-1 and Thiamine, 0.5 g L-1) were added into the media in the first setup, they were omitted in the latter for comparison. As a result, the highest hydrogen production (0.33 L H2 L-1 culture) was attained in the presence of supplements using 20 mM acetate. Similarly, the maximum amount of 5-ALA generation (16.54 mM) was achieved in 20 mM acetate containing medium under the same conditions. On the other hand, the greatest bacterial growth (OD660: 4.412, 2.162 g cdw L-1) was achieved in the absence of supplements using 40 mM acetate. To conclude, while element and vitamin supplementations promoted hydrogen and 5-ALA productions, absence of these had a positive effect on cell biomass. Specifically, the medium containing 20 mM acetate together with elements and vitamins could be suggested as the optimum growth culture for the highest hydrogen and 5-ALA productions.