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

- The carbon sources and lighting regime affected H2 production by P. kessleri.
- The highest yield of H2 in P. kessleri was obtained in the presence of acetate.
- P. kessleri did not able to produce H2 in darkness.
- Dark incubation after pre-illumination period enhanced H2 yield in P. kessleri.

Nowadays, hydrogen (H2) 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 H2 production by green microalga Parachlorella kessleri RA-002 newly isolated in Armenia. The results indicated that carbon sources and lighting regimes affected H2 production. In the presence of used carbon sources H2 production was observed, but the highest yield of H2 was obtained in the presence of acetate. It was 2-fold higher than the H2 yield determined in the presence of glucose. The increase of H2 production might be connected with the stimulation of H2-producing enzyme - [Fe]-hydrogenase synthesis. The data obtained show that acetate can be used as an effective carbon source in H2 production. H2 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 24 h, and then was moved in the darkness. H2 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 H2 production by microalgae.