초록
<P><B>Abstract</B></P><P>The overall goal of this research was to systematically evaluate H<SUB>2</SUB> production among different heterocystous cyanobacteria in response to defined experimental variables including N<SUB>2</SUB> and O<SUB>2</SUB> concentration, carbon source, and light intensity. N<SUB>2</SUB> elicited an immediate reduction of H<SUB>2</SUB> production rates and the magnitude of the effect was strikingly similar across the diverse collection of heterocystous cyanobacteria that were tested. At the N<SUB>2</SUB>:O<SUB>2</SUB> ratio found in air (4:1), N<SUB>2</SUB> was a much more potent inhibitor of H<SUB>2</SUB> production than O<SUB>2</SUB>. Low levels of O<SUB>2</SUB> (1–5% headspace, vol:vol) were generally found to support optimal H<SUB>2</SUB> production. Glucose addition (10 mM) stimulated light-dependent H<SUB>2</SUB> production in 8 of 10 cyanobacteria examined, eliciting a 2–11 fold increase in production rates and 2–45 fold increase in yields. The addition of glucose also effectively lowered the intensity of light required for optimal H<SUB>2</SUB> production in 4 of 10 strains tested. H<SUB>2</SUB> production rates ranged from 1 to 50 μmol mg chl <I>a</I><SUP>−1</SUP> h<SUP>−1</SUP>. The results from this study provide important benchmark phenotypes against which to evaluate newly discovered H<SUB>2</SUB>-producing heterocystous cyanobacteria, and we discuss how these findings highlight the necessity of a multi-parameter approach to comprehensively screen for superior H<SUB>2</SUB>-producing heterocystous cyanobacteria.</P> <P><B>Highlights</B></P><P>► N<SUB>2</SUB> is a more potent inhibitor of cyanobacterial H<SUB>2</SUB> production than O<SUB>2</SUB>. ► Most strains exhibit optimal H<SUB>2</SUB> production when atmospheric O<SUB>2</SUB> is maintained at 25%. ► Glucose typically increases cyanobacterial H<SUB>2</SUB> production rates and yields. ► Bioprospecting for H<SUB>2</SUB>-producing cyanobacteria requires a multifactorial approach.</P>