Environmental Engineering Reference
In-Depth Information
Table 11.4
Various light driven bio-hydrogen production methods
No
The process
Organisms
Key enzyme
Advantages
Disadvantages
1
Anaerobic photo-
synthetic under
N deficiency
Nitrogen fixing anoxy-
genic photosynthetic
bacteria
Nitrogenase
High rates, especially by purple non-sulfur
bacteria, might be activated by near-
infrared light; low sensitivity to high H
2
pressure
Sensitivity to N sources (due to repression
and inactivation of nitrogenase); needs
in simple organics as electron donor
for photosynthesis; narrow range of
organics; inactivation by oxygen; low
efficiency (needs in electrons and ATP)
2
Anaerobic photo-
synthetic under
over reduced
conditions
Anoxygenic photosyn-
thetic bacteria and
cyanobacteria under
anaerobic condi-
tions with reversible
hydrogenase (
hox YH
)
Hydrogenase
Relatively high efficiency (does not need
ATP)
At present knowledge appears only
during short-term experiments under
over-reduced conditions; high H
2
concentration inhibits the process; under
mesophilic conditions a possibility for
pathogenic bacteria development
3
Aerobic
photosynthetic
Nitrogen fixing
cyanobacteria
Nitrogenase
Converts light energy into H
2
fuel in stoi-
chiometry near to 2H
2
O < - > 2H
2
+ O
2
;
low sensitivity to high H
2
concentra-
tions; temporal or spatial separation of
O
2
and H
2
production
Low rates of the process; low efficiency
(needs in electrons and ATP)
4
Temporal separa-
tion of oxygenic
photosynthesis
and light-depen-
dent H
2
produc-
tion under sulfur
deprivation
Microalgae with Fe-Fe
hydrogenase; proved
for several species
including
Chlamydo-
monas
and
Chlorella
Hydrogenase
Converts light energy into H
2
fuel; long
term process; possibility to repeat the
cycle “oxygenic photosynthesis-light-
dependent H
2
production”
Low rates; high sensitivity to oxygen inac-
tivation; still need experimental studies
to determine efficiency of process
5
Aerobic
photosynthetic
Microalgae with Fe-Fe
hydrogenase
Hydrogenase
Converts light energy into H
2
fuel in stoi-
chiometry near to 2H
2
O < - > 2H
2
+ O
2
;
high efficiency; high rates of the process
Appears only during short-term experi-
ments at the start of anaerobic cultures
illumination; under S-deprivation shows
decreased rates but for longer period.
By-products under S-deprivation are
organic acids and ethanol
