Residual pigments and carbohydrates are separated from the hydrophilic phase
through dead-end or tangential flow membrane filtration (Gerardo et al. 2014;
Lorente et al. 2017; Marcati et al. 2014; Safi et al. 2014a, b; Schwenzfeier et al.
2011, 2014; Van Reis and Zydney 2001). Besides, membrane technologies can be
combined with other processes to increase selectivity by combining principles of
other fields (Demmer et al. 2005) for isolation of specific proteins using adsorbent
particles embedded in membrane pores or selective aqueous buffer systems for the
next fractioning step of carbohydrates and/or proteins (Weaver et al. 2013).
High-resolution chromatography has also been used for fractioning product
recovery. In a first step, Schwenzfeier et al. (2011) characterized Tetraselmis
sp. fractioning with a mild process and ionic exchange chromatography was used to
obtain protein. High purity can be also reached through ionic exchange chromatography and size exclusion chromatography for phycoerythrin from
Porphyridium cruentum (Bermejo et al. 2006; Cuellar-Bermudez et al. 2015).
Those highly purified proteins could be of interest for clinical and pharmacological
research as they can present some properties interesting for health, such as
antioxidant or anticancer activities.
3.1.5 Selective Extraction
Some techniques, such as ionic liquids, SFE, and ATPS, are applied to hydrophobic
phase for further separation of their different compounds (PUFAs, glycolipids,
phospholipids) from oily fraction. Solvent extraction or SFE is specifically used to
split up lipids and pigments (Cuellar-Bermudez et al. 2015; Grosso et al. 2015).
Innovative processes, such as direct transesterification during SFE, are commented
by Ranjith Kumar et al. (2015) and Taher et al. (2014) in reviews, but they need
deeper research for scaling up to industrial scale.
3.2 Processing Biomass to Obtain Energy
Processes involved in microalgae biomass transformation in the biofuel-driven
biorefineries are classified into direct combustion, thermochemical or biochemical
processing, and chemical transformation (see Fig. 2) involving the chemical
transformation of lipids extracted from biomass to produce biodiesel through
transesterification. All of them are explained in the following sections.
3.2.1 Direct Combustion
It is the most direct route to utilize microalgae biomass as fuel. Direct combustion is
a thermochemical technique used to burn biomass in the presence of excess air. In
theory, algae can be dried and burned. Combustion of algae for power generation
5 Microalgae Biorefineries for Energy …
109
through dead-end or tangential flow membrane filtration (Gerardo et al. 2014;
Lorente et al. 2017; Marcati et al. 2014; Safi et al. 2014a, b; Schwenzfeier et al.
2011, 2014; Van Reis and Zydney 2001). Besides, membrane technologies can be
combined with other processes to increase selectivity by combining principles of
other fields (Demmer et al. 2005) for isolation of specific proteins using adsorbent
particles embedded in membrane pores or selective aqueous buffer systems for the
next fractioning step of carbohydrates and/or proteins (Weaver et al. 2013).
High-resolution chromatography has also been used for fractioning product
recovery. In a first step, Schwenzfeier et al. (2011) characterized Tetraselmis
sp. fractioning with a mild process and ionic exchange chromatography was used to
obtain protein. High purity can be also reached through ionic exchange chromatography and size exclusion chromatography for phycoerythrin from
Porphyridium cruentum (Bermejo et al. 2006; Cuellar-Bermudez et al. 2015).
Those highly purified proteins could be of interest for clinical and pharmacological
research as they can present some properties interesting for health, such as
antioxidant or anticancer activities.
3.1.5 Selective Extraction
Some techniques, such as ionic liquids, SFE, and ATPS, are applied to hydrophobic
phase for further separation of their different compounds (PUFAs, glycolipids,
phospholipids) from oily fraction. Solvent extraction or SFE is specifically used to
split up lipids and pigments (Cuellar-Bermudez et al. 2015; Grosso et al. 2015).
Innovative processes, such as direct transesterification during SFE, are commented
by Ranjith Kumar et al. (2015) and Taher et al. (2014) in reviews, but they need
deeper research for scaling up to industrial scale.
3.2 Processing Biomass to Obtain Energy
Processes involved in microalgae biomass transformation in the biofuel-driven
biorefineries are classified into direct combustion, thermochemical or biochemical
processing, and chemical transformation (see Fig. 2) involving the chemical
transformation of lipids extracted from biomass to produce biodiesel through
transesterification. All of them are explained in the following sections.
3.2.1 Direct Combustion
It is the most direct route to utilize microalgae biomass as fuel. Direct combustion is
a thermochemical technique used to burn biomass in the presence of excess air. In
theory, algae can be dried and burned. Combustion of algae for power generation
5 Microalgae Biorefineries for Energy …
109