Photobiohydrogen production and high-performance photobioreactor - Solar Energy Sciences and Engineering Applications - page 351

Table 11.3.1 Genetic modification and metabolic engineering strategies to improve photobiohydrogen
production.

Problems Strategies Microorganisms References

Oxygen toxicity Attenuating the photosynthesis/ Chlamydomonas Melis (2007)

to enzymes respiration capacity ratio by DNA reinhardtii

insertional mutagenesis
Reducing the oxygen sensitivity of Synechococcus sp. Xu et al. (2005)

enzymes by engineering oxygen-
tolerant hydrogenase genes
Enhancing oxygen tolerance of Chlamydomonas Ghirardi et al. (2000)

hydrogenase by random and reinhardtii

directed mutagenesis

Lower Truncating the chlorophyll antenna Chlamydomonas Polle et al. (2003)

photosynthetic size of PSII to dissipate excessive reinhardtii

efficiency photons Rhodobacter Vasilyeva et al. (1999)

sphaeroides Kondo et al. (2002)

Insufficient Reducing the proton gradient Chlamydomonas Lee and Greenbaum

supply of across the thylakoid membrane reinhardtii (2003)

electrons and Increasing the availability of Chlamydomonas Kruse et al. (2005)

protons electrons and protons for hydrogen reinhardtii

evolution using a strain Stm6 with
modified respiratory metabolism
Increasing nitrogenase expression Rhodobacter Ozturk et al. (2006)

capsulatus

Presence of Removing the hupL gene Anabaena sp . Masukawa et al. (2002)

uptake Increasing the hydrogen evolution Thiocapsa Fodor et al. (2001)

hydrogenase capacity by a hypF-deficient mutant roseopersicina

Destroying the uptake hydrogenase Rhodobacter Kars et al. (2008)

genes by site directed mutagenesis sphaeroides

Lower ammonia Interrupting the genes coding for Rhodobacter Kim et al. (2008)

tolerance two PII-like proteins, GlnB and GlnK sphaeroides

Hence, interruption of the genes coding for two PII-like proteins from the chromosome
of Rhodobacter sphaeroides can make the glnB-glnK mutant exhibit less ammonium
ion-mediated repression for nitrogenase compared with its parental strain, resulting in
more hydrogen accumulation by the mutant under the conditions (Kim et al., 2008).
In summary, the incorporation of the genetic and metabolic engineering into the
cultivation of hydrogen-producing microorganisms has significantly improved the per-
formance of microorganisms in different aspects (Table 11.3.1). The oxygen toxicity to
enzymes for green algae and cyanobacteria can be weakened by alleviating the extreme
oxygen sensitivity to enzymes. Main measures include attenuating the photosynthe-
sis/respiration (P/R) capacity ratio, engineering oxygen-tolerant hydrogenase genes and
achieving the appropriate mutants. To enhance the transport of electrons, truncating
the chlorophyll antenna size is an effective approach to boost the photobiohydrogen
production rate for both photoautotrophic and photosynthetic bacteria. The suffi-
cient supply of electrons and protons can also be achieved by a genetic insertion of a
polypeptide protein channel. Additionally, to reduce the consumption of hydrogen by
the uptake hydrogenase, construction of a hydrogenase mutants or the removal of the