Enhanced hydrogen production by means of sulfur-deprived Chlamydomonas reinhardtii grown in preteated olive mill wastewater

Under sulfur-deprived conditions, the metabolism of Chlamydomonas reinhardtii switches to
the photoproduction of hydrogen. This process is sustained by both photosystem II-driven
water splitting and by the fermentation of stored carbohydrates. We investigated the
possibility of using diluted pretreated olive mill wastewaters (OMW), which contain
organic acids and sugars, as a substrate on which to grow Chlamydomonas, in order to
obtain suitable biomass to produce hydrogen. The cells grown on a mixture of pretreated
OMW and TAP (tris-acetate-phosphate) (50% dilution) were found to be richer in carbohydrates
and exhibited a greater production of hydrogen (150 ml H2 l-1 culture), compared
to the control cells (100 ml H2 l-1 culture). In these cultures, the hydrogen production
process was characterized by a shorter aerobic phase and a longer hydrogen-production
period. The results offer a useful perspective for the utilization of olive mill wastewaters,
which constitute an environmental problem, particularly in Mediterran areas, and for increasing the output for hydrogen production with Chlamydomonas.