Biological hydrogen production is done in a bioreactor based on the production of hydrogen by algae. Algae produce hydrogen under certain conditions. In the late 1990s it was discovered that if algae[clarify] are deprived of sulfur they will switch from the production of oxygen, as in normal photosynthesis, to the production of hydrogen.

Interesting article from Wikipedia. Read the full article here - http://en.wikipedia.org/wiki/Biological ... production

Which one is the best method to measure the concentrations of molecular hydrogen and oxygen produced in the photobioreactor?

I think Gas chromatography is the better way .