TY - JOUR
T1 - Powerful fermentative hydrogen evolution of photosynthate in the cyanobacterium Lyngbya aestuarii BL J mediated by a bidirectional hydrogenase
AU - Kothari, Ankita
AU - Parameswaran, Prathap
AU - Garcia-Pichel, Ferran
N1 - Publisher Copyright:
© 2014 Kothari, Parameswaran and Garcia-Pichel.
PY - 2014
Y1 - 2014
N2 - Cyanobacteria are considered good models for biohydrogen production because they are relatively simple organisms with a demonstrable ability to generate H2 under certain physiological conditions. However, most produce only little H2, revert readily to H2 consumption, and suffer from hydrogenase sensitivity to O2. Strains of the cyanobacteria Lyngbya aestuarii and Microcoleus chthonoplastes obtained from marine intertidal cyanobacterial mats were recently found to display much better H production potential. Because of their ecological origin in environments that become quickly anoxic in the dark, we hypothesized that this differential ability may have evolved to serve a role in the fermentation of the photosynthate. Here we show that, when forced to ferment internal substrate, these cyanobacteria display desirable characteristics of physiological H production. Among them, the strain L. aestuarii BL J had the fastest specific rates and attained the highest H concentrations during fermentation of photosynthate, which proceeded via a mixed acid fermentation pathway to yield acetate, ethanol, lactate, H, CO, and pyruvate. Contrary to expectations, the H yield per mole of glucose was only average compared to that of other cyanobacteria. Thermodynamic analyses point to the use of electron donors more electronegative than NAD(P)H in Lyngbya hydrogenases as the basis for its strong H production ability. In any event, the high specific rates and H concentrations coupled with the lack of reversibility of the enzyme, at the expense of internal, photosynthetically generated reductants, makes L. aestuarii BL J and/or its enzymes, a potentially feasible platform for large-scale H production.
AB - Cyanobacteria are considered good models for biohydrogen production because they are relatively simple organisms with a demonstrable ability to generate H2 under certain physiological conditions. However, most produce only little H2, revert readily to H2 consumption, and suffer from hydrogenase sensitivity to O2. Strains of the cyanobacteria Lyngbya aestuarii and Microcoleus chthonoplastes obtained from marine intertidal cyanobacterial mats were recently found to display much better H production potential. Because of their ecological origin in environments that become quickly anoxic in the dark, we hypothesized that this differential ability may have evolved to serve a role in the fermentation of the photosynthate. Here we show that, when forced to ferment internal substrate, these cyanobacteria display desirable characteristics of physiological H production. Among them, the strain L. aestuarii BL J had the fastest specific rates and attained the highest H concentrations during fermentation of photosynthate, which proceeded via a mixed acid fermentation pathway to yield acetate, ethanol, lactate, H, CO, and pyruvate. Contrary to expectations, the H yield per mole of glucose was only average compared to that of other cyanobacteria. Thermodynamic analyses point to the use of electron donors more electronegative than NAD(P)H in Lyngbya hydrogenases as the basis for its strong H production ability. In any event, the high specific rates and H concentrations coupled with the lack of reversibility of the enzyme, at the expense of internal, photosynthetically generated reductants, makes L. aestuarii BL J and/or its enzymes, a potentially feasible platform for large-scale H production.
KW - Bidirectional hydrogenase
KW - Cyanobacteria
KW - Fermentation
KW - Hydrogen
KW - Lyngbya aestuarii
KW - Microcoleus chthonoplastes
KW - Synechocystis
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U2 - 10.3389/fmicb.2014.00680
DO - 10.3389/fmicb.2014.00680
M3 - Article
AN - SCOPUS:84930504870
SN - 1664-302X
VL - 5
JO - Frontiers in Microbiology
JF - Frontiers in Microbiology
IS - DEC
M1 - 680
ER -