Characterization of light-dependent hydrogen production by new green microalga Parachlorella kessleri in various conditions.

Nowadays, hydrogen (H) production by green microalgae seems to be a very perspective, as stocks of water and solar energy are practically inexhaustible and renewable. The aim of this study was the optimization of conditions (organic carbon sources and lighting regime), which can provide light-dependent H production by green microalga Parachlorella kessleri RA-002 newly isolated in Armenia. The results indicated that carbon sources and lighting regimes affected H production. In the presence of used carbon sources H production was observed, but the highest yield of H was obtained in the presence of acetate. It was 2-fold higher than the H yield determined in the presence of glucose. The increase of H production might be connected with the stimulation of H-producing enzyme - [Fe]-hydrogenase synthesis. The data obtained show that acetate can be used as an effective carbon source in H production. H production by microalga (in the presence of acetate and glucose) was enhanced by 1.5-2.5-fold in comparison with continuously illuminated algal cells, when P. kessleri was illuminated during 24h, and then was moved in the darkness. H yield increase is possible due to hydrogenase activation and the creation of anaerobic conditions. This study was significant to find out available effective substrates and optimal lighting regime to provide with light-dependent H production by microalgae.