Biomedical Engineering Reference
In-Depth Information
used to rupture the algae cells, including autoclaving, microwave, sonication, osmotic
shock, and bead beating. Lee et  al. (2010) evaluated five different cell disruption
techniques for enhancing lipid extraction efficiency. They reported that the micro-
wave oven method is an efficient method for extracting lipids from microalgae.
Because of its simplicity and cost effectiveness, solvent extraction is widely used by
researchers (Letellier and Budzinski, 1999). For laboratory-scale studies, lipid con-
tent and composition can be determined using well-established techniques. The most
commonly used method for lipid extraction is the Bligh and Dyer method, or some
variation thereof. Methods for simultaneous extraction and transesterification of
algal biomass to extract the algal lipids are also available (Belarbi et al., 2000; Lewis
et al., 2000).
7.2
LIPID PROFILES
7.2.1 i dentiFiCation oF a lGae l lipid p roFiles
The steps involved in the upstream process for algal oil-based biodiesel production
include strain identification, optimization for higher lipid yield, and mass produc-
tion. For quantifying the lipids available in microalgae, any one of the following
chromatography techniques may be followed: high-pressure liquid chromatogra-
phy (HPLC), gas chromatography (GC), or chromatography-mass spectrometry
(LC/GC-MS). Usually, GC is employed for analyzing the algae lipid profiles after
conversion to FAMEs. GC-FID (flame ionization detection) or GC-MS may be used
for the identification of fatty acid profiles of algae lipids. In case of GC-FID, the
retention time for the individual components of FAMEs is compared to known stan-
dards (Mansour, 2005; Lin et al., 2007; Paik et al., 2009). The lipid profile of algal
oils can be analyzed via GC-FID using the ASTM D6584 and EN 14105 standard
methods. The methylated lipid/FAMEs of algae may contain traces of contaminants
such as chlorophylls, catalyst, or water, and samples injected in GC must be free
from these contaminants to prevent GC column damage.
7.2.2 s uitability oF a lGae l lipid For b iodiesel p roduCtion
In general, algal oils contain a higher degree of polyunsaturated fatty acids (PUFA)
(i.e., more than four double bonds) than vegetable oil (Belarbi et al., 2000; Harwood
and Guschina, 2009) and higher free fatty acid content (>2%). ASTM D6751 (United
States) and EN 14214 (European Union) provide the specifications for pure biodiesel
(B 100 , Table 7.1) and are used in many parts of world for comparing the fuel proper-
ties of biodiesel. The biodiesel standards developed in many countries are based on
the availability of region-specific biodiesel feedstocks. The specifications developed
for ensuring biodiesel fuel quality are frequently subjected to modifications, and
biodiesel-producing countries are required to update their specifications according
to changes in ASTM- or EN-based biodiesel standards.
The lipid composition of algal oil is different from plant oils/animal fats, and
it varies with species and growing conditions (Mutanda et  al., 2011). Major fuel
and chemical properties considered for the selection of an alternate diesel fuel are
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