Influence of light intensities on hydrogen production by sulfur-deprivedChlamydomonas reinhardtii

摘要

The green alga, Chlamydomonas reinhardti, is capable to sustained H2 production whengrown under sulfur-deprived conditions. It is known, that sulfur-deprivation graduallyinactivates PS II activity and leads to the establishment of anaerobiosis in the medium. The lostresults in hydrogenase induction in algae and hydrogen photoproduction for several days. Theinfluence of light intensity on the hydrogen production by sulfur-deprived Chlamydomonasreinhardtii was studied in long-term and short-term experiments in situ or in sampleswithdrawn from the PhBR. Overall hydrogen production by S-deprived culture was shown todepend on the light intensity with regions of light limitation and light inhibition. Optimalincident light intensities (I0) for maximum hydrogen production did not depend on the methodof sulfur deprivation and the initial acetate concentration (12-34 mM). At the same time, theoptimal I0 varied with the chlorophyll (Chl) concentration and the thickness of the vessel. Tocalculate the average light intensity in the PhBR, the special mathematics approach has beendeveloped. The optimal average light intensity for the overall H2 production was 30-40 μE m -2sec -1 and did not depend on the Chl and acetate concentrations and the method of sulfurdeprivation. Inhibitory effect of high light intensity is suppose to be due to enhanced oxygenaccumulation during the photosynthetic stage, and high activity of PSII at the beginning ofhydrogen production phase. Data suggest an important contribution of PSII in electronsfeeding to PSI through the whole process.