초록
<P><B>Abstract</B></P> <P>In this study, we tested four algal species (<I>Synechocystis</I> sp. PCC 6803 and three novel algal species isolated from Egyptian paddy rice soil, having high 16S rRNA gene sequence identity to <I>Nostoc spongiaeforme</I>, <I>Parachlorella kessleri</I> SAG 211-11 and <I>Nostoc</I> sp. PCC 7524) under aerobic, anaerobic and 3% CO<SUB>2</SUB>-supplemented anaerobic condition. Significant changes in photohydrogen production, morphology, chlorophyll <I>a</I> and protein content/pattern were observed in all species, when grown in these different conditions. H<SUB>2</SUB> production was higher in anaerobic condition in all species with the highest H<SUB>2</SUB> production rate of 4 mmol H<SUB>2</SUB> mg Chl<I>a</I> <SUP>−1</SUP> h<SUP>−1</SUP> at 24 h in <I>Synechocystis</I> sp. In contrast, Chl<I>a</I> content and protein content decreased (%) in <I>N. spongiaeforme</I>, (29%, 58%), <I>P. kessleri</I> (47%, 7%) and <I>Nostoc</I> sp. (59%, 65%).The anaerobic condition with 3% CO<SUB>2</SUB> stimulated early production of H<SUB>2</SUB> in all species except <I>Synechocystis</I> sp. Our results compared all selected algal species under different growth conditions for the screening of a superior H<SUB>2</SUB>-producing algal species that can help to address engineering challenges in the field of large-scale H<SUB>2</SUB> photoproduction by microalgae.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Microalgal H<SUB>2</SUB> production is both a promising and challenging biotechnological approach. </LI> <LI> Aerobic/anaerobic conditions significantly affect the metabolism of previously unidentified Egyptian microalgal strains. </LI> <LI> Anaerobic conditions promote H<SUB>2</SUB> production over aerobic conditions. </LI> <LI> Significant decrease in pigment yield and protein content was noted in anaerobic over aerobic conditions. </LI> <LI> Anaerobic conditions supplemented with CO<SUB>2</SUB> improved H<SUB>2</SUB> production rates by 3% in some species. </LI> </UL> </P>