Biomedical Engineering Reference
In-Depth Information
6.3.3
Development, Status, and Problems of Biological
Hydrogen Production
As early as the nineteenth century, people recognized that bacteria and algae could
produce molecular hydrogen. The oil crisis in the 1970s prompted awareness of
governments and scientists regarding the urgency of seeking alternative energy, with
biological hydrogen production first considered practically possible. Since then,
various biological hydrogen sources and hydrogen production technologies have
started to be researched. Currently, the dual pressure of energy and environment
resulted in the reemergence of biological hydrogen production research. A variety
of modern biotechnologies applied in biohydrogen production has greatly promoted
the development of biohydrogen production technology. At present, it is reported
that the hydrogen-producing taxa include photosynthetic organisms (photosynthetic
bacteria, cyanobacteria, and green algae); nonphotosynthetic organisms (obligate
anaerobic bacteria, facultative anaerobic bacteria); and archaeas. Special hydrogen
metabolism systems exist in these microorganisms. In general, different kinds of
microbial mechanisms and processes of hydrogen production are mainly the ones
discussed next.
6.3.3.1
Dark Fermentation Hydrogen Production
Nonphotosynthetic organisms that can produce hydrogen by dark fermentation
include obligate anaerobes, facultative anaerobes, and archaeas (e.g.,
Clostridium
butyricum
,
Clostridium acetobutylicm
,
Escherichia coli
,
Enterobacter aerogenes
,
Azotobacter chroococcum
,
Ruminococcus albus
,
Rhizobium
, etc.). Compared with
photosynthetic hydrogen production, dark fermentation has more advantages, such
as strong hydrogen-producing ability and rapid growth rate of the strains; wide
range of low-cost substrates; lack of need for alight source; and simple and
convenient reactor design, operation, and management. Compared with photosyn-
thetic hydrogen-producing strains, which mostly belong to the medium-temperature
(about 35
ı
C) type, the anaerobic fermentation hydrogen-producing strains belong
to the high-temperature type. They can produce hydrogen at about 55
ı
C, and at
high temperature, it is not easy to infect bacteria. Thus, the reaction conditions are
relatively easy to implement, and anaerobic fermentation hydrogen production is
easy to realize industrialization [
61
].
(1) Anaerobic fermentation hydrogen production
Fermentative hydrogen-producing strains mainly include four categories:
Enter-
obacter
,
Clostridium
,
Escherichia,
and
Bacillus
spp. Among them,
Enterobacter
spp. and
Clostridium
spp. are studied most. Fermentative hydrogen-producing
strains can utilize a variety of substrates to produce hydrogen catalyzed by nitro-
genase or hydrogenase. These substrates include formic acid, lactic acid, pyruvic
acid, short-chain fatty acids, glucose, starch, xylose, cellobiose, sulfide, and others.
