Value-Added Products from Microalgae - Biotechnological Applications of Microalgae - page 155

Harvesting and metabolite recovery methods depend on the nature of the species
and end-product. Centrifugation is probably the most reliable method of harvest-
ing but, on the other hand, it is costly. Filtration and flocculation are cost-effective
methods that are widely used for the harvesting of algal biomass. The cost of
the downstream recovery process for such high-value, high-purity products contrib-
utes to a significant portion of the overall production cost. For example, 60% of the
total production cost of EPA is attributed to the recovery process of EPA (Grima
et al., 2003), while biomass production only contributes approximately 40% of the
total production cost. Thus, reducing the cost of downstream processing can signifi-
cantly influence the overall economics of microalgal metabolite production (Grima
et al., 2003).
Genetic modification of microalgae has been considered for improving the yield
of valuable products at reduced costs (Milledge, 2011). The production of recom-
binant proteins in microalgal chloroplasts has several attributes (Specht, 2010).
Transgenic proteins can accumulate to much higher levels in the chloroplasts than
when expressed from the nuclear genome; chloroplasts can be transformed with
multiple genes in a single event due to multiple insertion sites (Specht, 2010).
Furthermore, proteins produced in chloroplasts are not glycosylated (Franklin and
Mayfield, 2005); this can be useful in the production of antibodies that are similar
to native antibodies in their ability to recognize their antigens (Specht, 2010). To
demonstrate the feasibility of human antibody expression in an algal system, a full-
length IgG (Immunoglobulin G) antibody has been synthesized in the chloroplast
of the green alga Chlamydomonas reinhardtii (Hempel et al., 2011). The ability to
accumulate high-value compounds makes microalgae attractive for recombinant
protein production; however, there are some factors that limit microalgal expres-
sion systems (Gong et al., 2011). These include the lack of standard procedures
for genetic transformation of commercially important microalgal species, limited
availability of molecular toolkits for genetic modification of microalgae, and low
expression levels of recombinant proteins (Surzycki et al., 2009).
The use of genetic modification may reduce the organic and natural appeal of
specific algal products, especially when the product is to be applied in the food
and feed industries. It is thus imperative to prioritize endeavors toward proper
species selection and production process development. This is a preferred
approach, rather than resorting to genetic engineering of microalgae. However, for
specialized applications, such as for therapeutic and diagnostic purposes, the use
of microalgae as bioreactors for the production of recombinant proteins may be
advantageous.
Microalgae boast a range of high-purity, valuable products that have progressed
successfully to commercialization in applications in the food, pharmaceutical, clini-
cal research, and animal nutrition industries. The possible employment of microalgae
in environmental applications (phycoremediaion and biofertilizers) provides poten-
tial solutions to global warming and sustainable economic development. Although
in their infancy, these applications hold significant promise, and with potential
use in diagnostics and therapeutics, the range of applications continues to grow.
However, for these industries to progress, it is important to start at grass-root levels
in research. Exhaustive screening procedures must be conducted for specific species