biofuel production, bioremediation, and greenhouse gas sequestration. Several useful bioproducts like lipids, proteins, vitamins, pigments, polysaccharides, and antioxidants are generated from algae (Brennan and Owende 2010). The influence of
freshwater pretreatment on S. muticum as a feedstock was investigated by Milledge
et al. (2018a). Yuan et al. (2018) extracted polysaccharides from the algae Ulva
prolifera using microwave technology and studied the properties and activities of
them. The commercial cultivation of microalgae for novel natural useful ingredients
has increased over the years. The connection between gas production and electron
transport pathway in sulfur-limited Chlamydomonas reinhardtii was studied by
Antal et al. (2009). Macro and microalgae are used for bioenergy production
(Carlsson et al. 2007) as they are extremely productive, simply harvestable, and
economical compared to different other sources used for bioenergy production.
Skjanes et al. (2013) analyzed the potential of microalgae in biohydrogen production
and other high-value bioproducts. The optimum temperature is 20–24
C, though
this might also differ with the culture medium and the species cultured (Brown et al.
1989). Most typically cultured microalgae withstand up to 27
C temperature, while
the temperature less than 16
C slows down algal growth. The temperatures above
35
C are inhibitory for a wide variety of species. Algal species isolation is not easy
due to the fact of the small cell dimension and the association with different
epiphytic species. Bacteria can be removed from the algae by way of washing or
plating with medium containing antibiotics. The various types of algal culture
methods include indoor or outdoor, open, axenic, batch, continuous, and
semicontinuous. Indoor cultures allow the control over operating conditions such
as temperature, nutrient level, illumination, and contamination. The axenic cultures
are free of any contamination and are sterilized. The limitations of the continuous
system are that these systems are highly expensive as constant illumination is
required.
Counting chambers are of two kinds, namely, Fuchs-Rosenthal and Burker,
which are used for a variety of cell sizes and concentrations. For a unique algal
species, dry weight per cell can also differ notably in accordance to the stress and
tradition conditions. Microalgae can additionally be viewed as a rich source of
ascorbic acid (Brown and Miller 1992). The dietary value of microalgae can differ
significantly according to the culture conditions. Culture medium used significantly
affects the metabolite production in various species of microalgae. Palanisamy et al.
(1991) have studied the application of algal cultures in shrimp hatcheries. Walsh
et al. (1987) have cultivated marine microalgae for producing bivalve seed. Principles for the cultivation of microalgae in photo-bioreactors were designed by Posten
(2009). Challenges and opportunities in microalgal bioreactors were explained by
Xu et al. (2009). The microorganisms in mixotrophic cultures grow quicker and may
synthesize hydrogen through autophytic and heterotrophic pathways (Ceron Garcia
et al. 2005). Dragone et al. (2010) have felt that mixotrophic conditions with
inorganic carbon and organic carbon such as aldohexose, glycerol, and acetate can
7 Sustainable Production of Hydrogen by Algae: Current Status and Future. . .
185
freshwater pretreatment on S. muticum as a feedstock was investigated by Milledge
et al. (2018a). Yuan et al. (2018) extracted polysaccharides from the algae Ulva
prolifera using microwave technology and studied the properties and activities of
them. The commercial cultivation of microalgae for novel natural useful ingredients
has increased over the years. The connection between gas production and electron
transport pathway in sulfur-limited Chlamydomonas reinhardtii was studied by
Antal et al. (2009). Macro and microalgae are used for bioenergy production
(Carlsson et al. 2007) as they are extremely productive, simply harvestable, and
economical compared to different other sources used for bioenergy production.
Skjanes et al. (2013) analyzed the potential of microalgae in biohydrogen production
and other high-value bioproducts. The optimum temperature is 20–24
C, though
this might also differ with the culture medium and the species cultured (Brown et al.
1989). Most typically cultured microalgae withstand up to 27
C temperature, while
the temperature less than 16
C slows down algal growth. The temperatures above
35
C are inhibitory for a wide variety of species. Algal species isolation is not easy
due to the fact of the small cell dimension and the association with different
epiphytic species. Bacteria can be removed from the algae by way of washing or
plating with medium containing antibiotics. The various types of algal culture
methods include indoor or outdoor, open, axenic, batch, continuous, and
semicontinuous. Indoor cultures allow the control over operating conditions such
as temperature, nutrient level, illumination, and contamination. The axenic cultures
are free of any contamination and are sterilized. The limitations of the continuous
system are that these systems are highly expensive as constant illumination is
required.
Counting chambers are of two kinds, namely, Fuchs-Rosenthal and Burker,
which are used for a variety of cell sizes and concentrations. For a unique algal
species, dry weight per cell can also differ notably in accordance to the stress and
tradition conditions. Microalgae can additionally be viewed as a rich source of
ascorbic acid (Brown and Miller 1992). The dietary value of microalgae can differ
significantly according to the culture conditions. Culture medium used significantly
affects the metabolite production in various species of microalgae. Palanisamy et al.
(1991) have studied the application of algal cultures in shrimp hatcheries. Walsh
et al. (1987) have cultivated marine microalgae for producing bivalve seed. Principles for the cultivation of microalgae in photo-bioreactors were designed by Posten
(2009). Challenges and opportunities in microalgal bioreactors were explained by
Xu et al. (2009). The microorganisms in mixotrophic cultures grow quicker and may
synthesize hydrogen through autophytic and heterotrophic pathways (Ceron Garcia
et al. 2005). Dragone et al. (2010) have felt that mixotrophic conditions with
inorganic carbon and organic carbon such as aldohexose, glycerol, and acetate can
7 Sustainable Production of Hydrogen by Algae: Current Status and Future. . .
185