Optimization of metabolic capacity and flux through environmental cues to maximize hydrogen production by the cyanobacterium "Arthrospira (Spirulina) maxima"

Ananyev, GM, Carrieri D, Dismukes GC.  2008.  

Journal:

Applied and Environmental Microbiology

Volume Number:

74

Pages:

6102-6113

Abstract:

Environmental and nutritional conditions that optimize the yield of hydrogen (H-2) from water using a two-step photosynthesis/ fermentation (P/F) process are reported for the hypercarbonate-requiring cyanobacterium "Arthrospira maxima." Our observations lead to four main conclusions broadly applicable to fermentative H-2 production by bacteria: (i) anaerobic H-2 production in the dark from whole cells catalyzed by a bidirectional [NiFe] hydrogenase is demonstrated to occur in two temporal phases involving two distinct metabolic processes that are linked to prior light-dependent production of NADPH (photosynthetic) and dark/anaerobic production of NADH (fermentative), respectively; (ii) H-2 evolution from these reductants represents a major pathway for energy production (ATP) during fermentation by regenerating NAD(+) essential for glycolysis of glycogen and catabolism of other substrates; (iii) nitrate removal during fermentative H-2 evolution is shown to produce an immediate and large stimulation of H-2, as nitrate is a competing substrate for consumption of NAD(P) H, which is distinct from its slower effect of stimulating glycogen accumulation; (iv) environmental and nutritional conditions that increase anaerobic ATP production, prior glycogen accumulation (in the light), and the intracellular reduction potential (NADH/NAD(+) ratio) are shown to be the key variables for elevating H-2 evolution. Optimization of these conditions and culture age increases the H-2 yield from a single P/F cycle using concentrated cells to 36 ml of H-2/g (dry weight) and a maximum 18% H-2 in the headspace. H-2 yield was found to be limited by the hydrogenase-mediated H-2 uptake reaction.

Notes:

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Related External URL:

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Citation:
Ananyev, GM, Carrieri D, Dismukes GC.  2008.  Optimization of metabolic capacity and flux through environmental cues to maximize hydrogen production by the cyanobacterium "Arthrospira (Spirulina) maxima". Applied and Environmental Microbiology. 74:6102-6113.