like genetic diversity and possess numerous physiological and biochemical characteristics apart from generation of abundant carbohydrates and lipids. Still, several
microalgae needs to be explored for cultivation, and there metabolism needs to be
understood for any genetic modification to generate strains which are capable of
higher hydrogen production (Wang et al. 2014). Borowitzka (1999) felt that industrial biomass production of microalgae through phototrophic approach is the most
viable and economical, and many factors like light intensity, pH, temperature,
salinity, vapor content, and nutrients have an effect on the microalgal cultivation.
Ras et al. (2011) reported that Scenedesmus, Spirulina, and genus Ulva have the
potential to produce biogas. Taihu blue alga was investigated for biogas production
with corn straw as a carbon source (Zhong et al. 2012). Production of biogas from
macroalgal waste streams for bioenergy generation was investigated by Tedesco and
Stokes (2017) in Eire. Vergara-Fernandez et al. (2008) reported that algal species
like Macrocystis pyrifera generated biogas in anaerobic reactor. Mussgnug et al.
(2010) reported that the microalgal species C. reinhardtii and Scenedesmus obliquus
can be used as substrates for fermentative biogas production. They additionally
reported that heat, salt levels, and macromolecule content have an effect on the
biogas yield. Pretreatment could enhance the biogas production (Kavitha et al.
2017). Bayro-Kaiser and Nelson (2016) mutagenized C. reinhardtii to come up
with mutants that exhibited temperature-sensitive photoautotrophic growth.
Eilenberg et al. (2016) generated the HydA enzyme and reported that the in vivo
enzymatic activity of the Fd-HydA enzyme is more than that of the native HydA and
shows higher gas tolerance. Under sulfur deprivation, hydrogen formation from
algae was reported (Skjanes et al. 2013).
Batyrova and Hallenbeck (2017) reported about the genetically modified
Chlamydomonas reinhardtii strain cy6Nac2.49, which was suitable for hydrogen
generation. Krassen et al. (2009) studied the stepwise assembly of photosystem I and
hydrogen evolution. Melis and associates discovered that sulfur limitation caused
production of hydrogen in light by Chlamydomonas reinhardtii (Melis et al. 2000).
Satoh et al. (2002) studied the regulation of energy balance in photosystems.
Techno-economic analysis of microalgal biofuels was done by Stephens et al.
(2010). The effect of pH and a methanogenic matter addition on hydrogen production was studied by Kumar et al. (2016). The promising way forward for microalgae
as a renewable source of energy was reviewed by Khan et al. (2018). Melis et al.
(2000) have reported that microalgae that produce polysaccharide will also produce
biohydrogen along with methane in anaerobic conditions. A review of algal
biohydrogen production was done by Rathore and Singh (2013). Genetic improvement of microalgae for biohydrogen production was investigated by Oncel et al.
(2015a). Anaerobic membrane bioreactors for biohydrogen production were studied
by Aslam et al. (2018). Show et al. (2012) reviewed the current status of
biohydrogen production. Li et al. (2020) have studied microalgae for biofuel production. Shaikh Abdur et al. (2017) have reviewed the possibilities of growing
microalgae in wastewater. Investigations on the cultural conditions required for
growing Chlorella vulgaris were optimized by Daliry et al. (2017). Saba et al.
(2017) have used bacteria and algae in microbial fuel cells for generation of
188
R. Kumar et al.
microalgae needs to be explored for cultivation, and there metabolism needs to be
understood for any genetic modification to generate strains which are capable of
higher hydrogen production (Wang et al. 2014). Borowitzka (1999) felt that industrial biomass production of microalgae through phototrophic approach is the most
viable and economical, and many factors like light intensity, pH, temperature,
salinity, vapor content, and nutrients have an effect on the microalgal cultivation.
Ras et al. (2011) reported that Scenedesmus, Spirulina, and genus Ulva have the
potential to produce biogas. Taihu blue alga was investigated for biogas production
with corn straw as a carbon source (Zhong et al. 2012). Production of biogas from
macroalgal waste streams for bioenergy generation was investigated by Tedesco and
Stokes (2017) in Eire. Vergara-Fernandez et al. (2008) reported that algal species
like Macrocystis pyrifera generated biogas in anaerobic reactor. Mussgnug et al.
(2010) reported that the microalgal species C. reinhardtii and Scenedesmus obliquus
can be used as substrates for fermentative biogas production. They additionally
reported that heat, salt levels, and macromolecule content have an effect on the
biogas yield. Pretreatment could enhance the biogas production (Kavitha et al.
2017). Bayro-Kaiser and Nelson (2016) mutagenized C. reinhardtii to come up
with mutants that exhibited temperature-sensitive photoautotrophic growth.
Eilenberg et al. (2016) generated the HydA enzyme and reported that the in vivo
enzymatic activity of the Fd-HydA enzyme is more than that of the native HydA and
shows higher gas tolerance. Under sulfur deprivation, hydrogen formation from
algae was reported (Skjanes et al. 2013).
Batyrova and Hallenbeck (2017) reported about the genetically modified
Chlamydomonas reinhardtii strain cy6Nac2.49, which was suitable for hydrogen
generation. Krassen et al. (2009) studied the stepwise assembly of photosystem I and
hydrogen evolution. Melis and associates discovered that sulfur limitation caused
production of hydrogen in light by Chlamydomonas reinhardtii (Melis et al. 2000).
Satoh et al. (2002) studied the regulation of energy balance in photosystems.
Techno-economic analysis of microalgal biofuels was done by Stephens et al.
(2010). The effect of pH and a methanogenic matter addition on hydrogen production was studied by Kumar et al. (2016). The promising way forward for microalgae
as a renewable source of energy was reviewed by Khan et al. (2018). Melis et al.
(2000) have reported that microalgae that produce polysaccharide will also produce
biohydrogen along with methane in anaerobic conditions. A review of algal
biohydrogen production was done by Rathore and Singh (2013). Genetic improvement of microalgae for biohydrogen production was investigated by Oncel et al.
(2015a). Anaerobic membrane bioreactors for biohydrogen production were studied
by Aslam et al. (2018). Show et al. (2012) reviewed the current status of
biohydrogen production. Li et al. (2020) have studied microalgae for biofuel production. Shaikh Abdur et al. (2017) have reviewed the possibilities of growing
microalgae in wastewater. Investigations on the cultural conditions required for
growing Chlorella vulgaris were optimized by Daliry et al. (2017). Saba et al.
(2017) have used bacteria and algae in microbial fuel cells for generation of
188
R. Kumar et al.