Page 499 - Refining Biomass Residues for Sustainable Energy and Bioproducts

456 Refining Biomass Residues for Sustainable Energy and Bioproducts

grown in an optimum condition, their growth rate is too slow (Lassing, et al.,
2008). It is one of the most promising biofuel producing microalgae due to its high
lipid content. B. braunii is a little unusual in the secretion of lipids in the extracellu-
lar medium, whereas other microalgae have cytoplasmic lipids (Hirose et al., 2013).

20.3.2.3 Pleurochrysis carterae

The unicellular microalgae, Pleurochrysis carterae, have a unique ability of calcifi-
cation process occurring at the subcellular level to produce calcified scales. This
type of microalgae can be commercially used for the production of biodiesel due to
their lipid content. It is a fast growing organism with low risk of contamination
(Rahbari, 2009).

20.3.2.4 Dunaliella salina

The biflagellate green microalgae, Dunaliella salina, belong to the family
Dunalliellacea. It is predominantly found in high salt regions commonly in marine
waters. Due to its high amount of carotenoids and its antioxidant activity, it is
regarded as a food source. It is also used for the biodiesel production due to its
methylation of fatty acids, such as linolenic and palmetic acids (Oren, 2005).

20.3.3 Macroalgae

20.3.3.1 Gracilaria chilensis
The red macroalgae Gracilaria chilensis have been reported to produce higher
amounts of biomass when compared to other macroalgae (Wi et al., 2009). Due to
the high content of polysaccharides, it is useful for the production of bioethanol by
the method called hydrolysis. After the extraction of biomass, it can be used for
producing other value-added by-products.

20.3.3.2 Sargassum angustifolium
The brown algae Sargassum angustifolium are abundantly present in the Persian
Gulf, which is used for the production of biodiesel and other value-added by-
products. After the extraction of biofuel, S. angustifolium is mainly used for
the production of sodium alginate. The biomass obtained after the alginate produc-
tion is used for bioethanol production by fermentation method. The macroalgal
S. angustifolium biomass can be used as the substitute for yeast during ethanolic
fermentation (Ardalan et al., 2018). The bioethanol production from S. angustifo-
lium biomass should be pretreated with acid (Yazdani et al., 2015). This pretreat-
ment step disrupts the recalcitrant structure completely and evolves nitrogen gas
that can be used for the fermentation, thus cutting down the cost of nutrients
required for the process.