cycle, and (3) diplobiontic life cycle (Diaz-Pulido and McCook 2008). Marine
macroalgae such as Rhodophyta, Ochrophyta, and Chlorophyta phyla are widely
studied due to their applications (Barsanti et al. (2008) ). Traditionally, they were
cultivated from the sea directly. Lately, macroalgae cultivation methodologies have
been improvised (Sahoo and Yarish 2005; Kim et al. 2017). Macroalgal species
belonging to Undaria, Sargassum, Saccharina (Laminaria), Kappaphycus alvarezii,
Porphyra, Eucheuma denticulatum, Gracilaria, Gelidium, Saccharina, and
Lessonia have applications in food and medicine. Main genera were Kappaphycus,
Gracilaria, Eucheuma, Porphyra, Saccharina japonica, and Sargassum fusiforme.
The idea behind the use of macroalgae for bioenergy generation is that they are rich
in polysaccharides which make them potential candidates for bioenergy generation
(Kraan 2013). There process would become economically feasible only if it is
coupled with production of valuable bioproducts (Balina et al. 2017). Brown algae
contain alginates and fucoidans and laminarin, while red algae contain agar, carrageenans, xylans, and mannans. Xylans, sulfated galactans, and ulvanes are present in
green algae. Hydrogen produced by macroalgae is attractive for renewable energy
due to their rapid growth (Luning and Pang 2003). The most cultivated are Undaria
pinnatifida, Laminaria japonica, Gracilaria, Eucheuma, Porphyra and
Kappaphycus, Enteromorpha, Monostroma, Laminaria japonica, Porphyra,
Eucheum, and Enteromorpha. Gendy and El-Temtamy (2013) suggested that
microalgae-based energy fuels are eco-friendly and nontoxic. Kraan (2010) observed
that some macroalgae gather a high quantity of carbohydrates for the assembly of
biofuels. Park et al. (2011) have reported that Gelidium amansii can produce
biohydrogen by anaerobic fermentation. Prospects of hydrogen production by
algae were reviewed by Prince and Kheshgi (2005). Anabaena was pretreated with
the enzyme to generate biohydrogen (Nayak et al. 2014). Sparging the cultures of
Mastigocladus laminosus with gases was used for biohydrogen production
(Miyamoto et al. 1979). Aerobic and anaerobic phases, light intensity, and mixing
speed of Chlamydomonas reinhardtii were investigated by simulation of environmental conditions by Oncel et al. (2015b). Various algae used for hydrogen production are tabulated (Table 7.1).
7.5 Mechanism of Hydrogen Production by Algae
Hydrogen can be produced by the following methods: dissociation of water in the
presence of sunlight into hydrogen and oxygen which is termed direct photolysis
(Johnston et al. 2005).
H 2 O ! H 2 + ½O 2 .
Microalgae can carry out photosynthesis in the presence of light (Ghirardi et al.
2000). Indirect photolysis splits water molecules in sunlight forming oxygen
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R. Kumar et al.
macroalgae such as Rhodophyta, Ochrophyta, and Chlorophyta phyla are widely
studied due to their applications (Barsanti et al. (2008) ). Traditionally, they were
cultivated from the sea directly. Lately, macroalgae cultivation methodologies have
been improvised (Sahoo and Yarish 2005; Kim et al. 2017). Macroalgal species
belonging to Undaria, Sargassum, Saccharina (Laminaria), Kappaphycus alvarezii,
Porphyra, Eucheuma denticulatum, Gracilaria, Gelidium, Saccharina, and
Lessonia have applications in food and medicine. Main genera were Kappaphycus,
Gracilaria, Eucheuma, Porphyra, Saccharina japonica, and Sargassum fusiforme.
The idea behind the use of macroalgae for bioenergy generation is that they are rich
in polysaccharides which make them potential candidates for bioenergy generation
(Kraan 2013). There process would become economically feasible only if it is
coupled with production of valuable bioproducts (Balina et al. 2017). Brown algae
contain alginates and fucoidans and laminarin, while red algae contain agar, carrageenans, xylans, and mannans. Xylans, sulfated galactans, and ulvanes are present in
green algae. Hydrogen produced by macroalgae is attractive for renewable energy
due to their rapid growth (Luning and Pang 2003). The most cultivated are Undaria
pinnatifida, Laminaria japonica, Gracilaria, Eucheuma, Porphyra and
Kappaphycus, Enteromorpha, Monostroma, Laminaria japonica, Porphyra,
Eucheum, and Enteromorpha. Gendy and El-Temtamy (2013) suggested that
microalgae-based energy fuels are eco-friendly and nontoxic. Kraan (2010) observed
that some macroalgae gather a high quantity of carbohydrates for the assembly of
biofuels. Park et al. (2011) have reported that Gelidium amansii can produce
biohydrogen by anaerobic fermentation. Prospects of hydrogen production by
algae were reviewed by Prince and Kheshgi (2005). Anabaena was pretreated with
the enzyme to generate biohydrogen (Nayak et al. 2014). Sparging the cultures of
Mastigocladus laminosus with gases was used for biohydrogen production
(Miyamoto et al. 1979). Aerobic and anaerobic phases, light intensity, and mixing
speed of Chlamydomonas reinhardtii were investigated by simulation of environmental conditions by Oncel et al. (2015b). Various algae used for hydrogen production are tabulated (Table 7.1).
7.5 Mechanism of Hydrogen Production by Algae
Hydrogen can be produced by the following methods: dissociation of water in the
presence of sunlight into hydrogen and oxygen which is termed direct photolysis
(Johnston et al. 2005).
H 2 O ! H 2 + ½O 2 .
Microalgae can carry out photosynthesis in the presence of light (Ghirardi et al.
2000). Indirect photolysis splits water molecules in sunlight forming oxygen
190
R. Kumar et al.